# A search for passive protoplanetary disks in the Taurus-Auriga star-forming region

Gaspard Duchene, Adam Becker, Yizhe Yang, H. Bouy, Robert J. de Rosa,

Jennifer Patience, Julien H. Girard

► To cite this version:

Gaspard Duchene, Adam Becker, Yizhe Yang, H. Bouy, Robert J. de Rosa, et al. A search for passive protoplanetary disks in the Taurus-Auriga star-forming region. Monthly Notices of the Royal Astronomical Society, 2017, 469 (2), pp.1783-1808. 10.1093/mnras/stx852. hal-01509502

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# A search for passive protoplanetary discs in the Taurus–Auriga star-forming region

Gaspard Duchêne,<fnref n="1" />,<fnref n="2" />* Adam Becker,<fnref n="1" /> Yizhe Yang,<fnref n="3" /> Hervé Bouy,<fnref n="4" />,<fnref n="5" />
Robert J. De Rosa,<fnref n="1" /> Jennifer Patience<fnref n="6" /> and Julien H. Girard<fnref n="2" />,<fnref n="7" />

Accepted 2017 April 4. Received 2017 March 23; in original form 2016 November 21

## ABSTRACT

We conducted a 12-month monitoring campaign of 33 T Tauri stars (TTS) in Taurus. Our goal was to monitor objects that possess a disc but have a weak $H\alpha$ line, a common accretion tracer for young stars, in order to determine whether they host a passive circumstellar disc. We used medium-resolution optical spectroscopy to assess the accretion status of the objects and to measure the $H\alpha$ line. We found no convincing examples of passive discs: only transition disc and debris disc systems in our sample are non-accreting. Among accretors, we found no example of flickering accretion, leading to an upper limit of 2.2 per cent on the duty cycle of accretion gaps, assuming that all accreting TTS experience such events. When combining literature results with our observations, we found that the reliability of traditional $H\alpha$-based criteria to test for accretion is high but imperfect, particularly for low-mass TTS. We found a significant correlation between stellar mass and the full width at 10 per cent of the peak ($W_{10}$) of the $H\alpha$ line that does not seem to be related to variations in free-fall velocity. Finally, our data revealed a positive correlation between the $H\alpha$ equivalent width and its $W_{10}$, indicative of a systematic modulation in the line profile whereby the high-velocity wings of the line are proportionally more enhanced than its core when the line luminosity increases. We argue that this supports the hypothesis that the mass accretion rate on the central star is correlated with the $H\alpha W_{10}$ through a common physical mechanism.

**Key words:** circumstellar matter – stars: variables: T Tauri, Herbig Ae/Be.

## 1 INTRODUCTION

T Tauri stars (TTS) are pre-main-sequence stars with masses $M \lesssim 1.5 M_{\odot}$. Many of these objects host circumstellar discs that can be traced by the thermal emission of the dust they contain (Haisch, Lada & Lada 2001; Ribas et al. 2014). Sensitive infrared surveys with the *Spitzer* and *Herschel* observatories have identified thousands of TTS with fully sampled spectral energy distributions (SEDs) in nearby star-forming regions and have enabled statistical studies of the evolution of protoplanetary discs (Williams & Cieza 2011; Alexander et al. 2014, and references therein). While most TTS present a full-fledged excess extending from the near-infrared to the millimetre regime, these surveys have also revealed a number

of objects whose excess is significantly subdued, sometimes even completely absent, in the near- to mid-infrared regime. The existence of transition discs, in which the inner regions of the disc are almost entirely devoid of dust (and gas), suggests that the opening of an inner hole is an important step in the disc dissipation process, although debate about the physical mechanism(s) responsible for this hole opening is ongoing (Espaillat et al. 2014).

Dissipative forces in the gaseous component of protoplanetary discs are responsible for angular momentum transport in these discs, which ultimately leads to accretion on the central star (Bertout 1989; Hartmann, Hercez & Calvet 2016). This accretion process is believed to be magnetically mediated and, as a side effect, is also responsible for the launching of collimated jets (Bouvier et al. 2007a). TTS displaying evidence for accretion and mass loss are referred to as ‘classical’ TTS (CTTS). Pre-main-sequence stars of the same age with no evidence for ongoing accretion are dubbed ‘weak-lined’

<footnote n="1">¹Astronomy Department, University of California, Berkeley, CA 94720, USA</footnote>

<footnote n="2">²Université Grenoble Alpes, CNRS, IPAG, Grenoble, F-38000, France</footnote>

<footnote n="3">³Physics Department, University of California, Berkeley, CA 94720, USA</footnote>

<footnote n="4">⁴Laboratoire d'Astrophysique de Bordeaux, Université Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, F-33615 Pessac, France</footnote>

<footnote n="5">⁵Centro de Astrobiología, Departamento de Astrofísica, INTA-CSIC, PO Box 78, 28691, ESAC Campus, E-208691 Villanueva de la Cañada, Madrid, Spain</footnote>

<footnote n="6">⁶School of Earth and Space Exploration, Arizona State University, PO Box 871404, Tempe, AZ 85287, USA</footnote>

<footnote n="7">⁷European Southern Observatory, Casilla 19001, Santiago 19, Chile</footnote>

<footnote>* E-mail: gduchene@berkeley.edu</footnote>
TTS (WTTS). For magneto-accretion to proceed, the circumstellar disc must extend all the way to the co-rotation radius, which is located just a few stellar radii away from the star. In this scenario, if an inner hole is carved out as part of the disc evolution, accretion would be expected to stop. Indeed, in an inside-out disc-clearing picture, accretion is expected to stop before a significant signature builds up in the SED of the system, specifically a deficit of near-infrared excess. In other words, while the presence of a protoplanetary disc and ongoing accretion have been assumed to go systematically hand-in-hand, it is possible that some objects may show one but not the other. Indeed, the correlation between active accretion and the presence of a full-fledged disc has proved to be less automatic than initially expected. A number of examples of significant infrared excess have been discovered among WTTS (Padgett et al. 2006; Cieza et al. 2013; Fang et al. 2013), and some transitional discs have been found to accrete at a rate comparable to that of normal CTTS (e.g. Najita, Strom & Muzerolle 2007). The former category is particularly intriguing, as these ‘passive’ (i.e. non-accreting) circumstellar discs could represent a key initial stage of disc dissipation (e.g. McCabe et al. 2006).

The energy deposited by accretion on the star is radiated away through a combination of hot continuum and line emission. As a consequence of the characteristic $10^4$ K temperature of an accretion hotspot, most of the continuum is emitted at ultraviolet wavelengths, and observations in this regime are the most sensitive and best quantitative tracers of the mass accretion rate (Gullbring et al. 1998; Herczeg & Hillenbrand 2008; Rigliaco et al. 2011; Ingleby et al. 2013). However, the intrinsically red colours of TTS and the common presence of significant line-of-sight extinction often preclude the use of this diagnostic of accretion. Instead, line emission is the most commonly used tracer of accretion in TTS. While many lines throughout the optical and near-infrared wavelength range correlate strongly with UV-determined accretion rates (Antoniucci et al. 2011; Rigliaco et al. 2012), the $H\alpha$ line remains the most common tracer of accretion by virtue of its being the strongest emission line, despite a significant contribution from chromospheric activity and stellar winds and outflows. In particular, TTS have long been characterized as accreting if their $H\alpha$ equivalent width (EW) exceeds a spectral-type-dependent threshold set to distinguish them from chromospherically active stars (Barrado y Navascués & Martín 2003, and references therein). However, it has been suggested that the intrinsic linewidth, specifically $W_{10}$, is a more accurate discriminator between accreting and non-accreting TTS (White & Basri 2003; Natta et al. 2004), as chromospheric activity is generally characterized by much lower velocities than organized accretion flows. It must be pointed out, however, that different studies yield somewhat different accretion thresholds (Cieza et al. 2013; Fang et al. 2013). Nonetheless, the observed correlation between $W_{10}$ and the mass accretion rate has led to the idea that measuring the line width of $H\alpha$ can provide a quantitative estimate of the accretion rate (Natta et al. 2004). Considering the line-of-sight velocities involved, medium- to high-resolution spectroscopy is necessary to measure $W_{10}$. This means that this quantity is generally not probed when performing reconnaissance surveys of TTS, leaving the EW as the common, albeit imperfect, criterion used to determine the accretion status of TTS.

Accretion on young stellar objects is a highly variable phenomenon. Indeed, photometric variability was one of the original criteria used to identify such objects (Joy 1945; Herbig 1960). Leaving aside the most extreme FU Ori-like outbursts (Audard et al. 2014), TTS are known to display variability in their accretion rate of the order of 0.5 dex on time-scales ranging from hours to

years (Alencar & Batalha 2002; Nguyen et al. 2009; Fang et al. 2013; Costigan et al. 2014; Venuti et al. 2014). In this context, it is plausible that the apparent conundrum posed by WTTS with full-fledged discs could be a consequence of some extreme cases of variability. If the accretion rate varies so much as to effectively flicker on and off, single-epoch probes of accretion may not yield the full picture for any particular object. However, TTS for which the accretion flow is known to temporarily pause altogether have proved remarkably elusive (e.g. Costigan et al. 2012), with only one relatively old (~8 Myr) TTS being flagged as undergoing episodic accretion to date (Murphy et al. 2011).

An alternative interpretation of the apparently passive discs is that past spectroscopic classification was inaccurate. It is possible, for instance, that self-absorption in the $H\alpha$ line profile, a common occurrence among CTTS, remains undetected in low-resolution spectra, resulting in a low EW for the emission line (Fang et al. 2013). In such cases, the level of accretion can be more readily assessed by measuring the $H\alpha W_{10}$ if its correlation with the accretion rate is rooted in a physical mechanism. This could be particularly valuable in the case of weakly accreting TTS, for which the UV excess diagnostic is not easy to probe, especially for M-type objects (Venuti et al. 2014).

Here we present the results of a 12-month medium-resolution spectroscopic monitoring campaign aimed at identifying permanently passive discs and/or discs experiencing flickering accretion in a sample of 31 disc-bearing TTS in the Taurus star-forming region. The targets were selected to represent as broad a diversity of accretion states as possible, from apparently non-accreting WTTS to strongly accreting CTTS. The paper is organized as follows. Section 2 discusses the choices made in the practical implementation of this description, and Section 3 presents the observations and data reduction details. The main results of the survey and their analysis are presented in Section 4. Finally, the lack of confirmed passive discs, the general variability trends observed in this study, and the pertinence of the $H\alpha$ in assessing the accretion status of TTS are discussed in Section 5. Section 6 summarizes our main results.

## 2 SURVEY METHODOLOGY

### 2.1 Set-up of the campaign

#### 2.1.1 Instrumental configuration

While observations dedicated to accurately measuring the $H\alpha$ line profile and $W_{10}$ use high-resolution spectroscopy ($R \gtrsim 25\,000$), such settings require relatively long integration times that are not amenable to extensive monitoring campaigns of large samples. In order to circumvent this issue, and to obtain as many epochs as possible, we have instead adopted a strategy based on a medium spectral resolution. In order to estimate the spectral resolution necessary to achieve our goal, we used a toy model in which the $H\alpha$ line is approximated by a Gaussian profile, which is reasonable for objects with relatively narrow emission lines. In this situation, the observed $W_{10}$ of the line and its full width at half-maximum (FWHM) are connected by the relationship $W_{10} \approx 1.82$ FWHM. Thus, a $W_{10}$ of $200 \text{ km s}^{-1}$ (the lowest proposed threshold demarcating accreting from non-accreting TTS, Natta et al. 2004) corresponds to a FWHM of $110 \text{ km s}^{-1}$. Such a line can be spectrally resolved if $R \gtrsim 2700$ (achieved during the majority of our observations), assuming a high signal-to-noise ratio. This toy model, which neglects the effects of instrumental line broadening and limited spectral sampling, served as a rough guideline for selecting the instrumental
set-ups used in the survey. In Section 4.2, we present a quantitative analysis of the accuracy of the *W*₁₀ measurements using actual data.

While the primary focus of the survey is the Hα line (see below), other accretion-related emission lines are present in optical spectra of TTS (e.g. Herczeg & Hillenbrand 2008; Fang et al. 2009; Rigliaco et al. 2012), providing additional elements of analysis in cases where Hα measurements are ambiguous (Jayawardhana et al. 2006). In particular, we make use of the 5876- and 6678-Å He I emission lines. In addition, when a wide spectral coverage is available, we also include the 8498–8662-Å Ca triplet, which is also directly connected to accretion in TTS. Finally, we also consider the 6300-Å [O I] forbidden emission line, one of the strongest tracers of mass loss in young low-mass stars, which indirectly reveals underlying accretion on the central object (Hartigan, Edwards & Ghandour 1995). We note, however, that the detection of the [O I] line can be ambiguous at the medium resolution adopted here, as atmospheric glow also produces line emission. We thus put less emphasis on that line than on the He I and Ca lines.

## 2.1.2 Temporal sampling

Because accretion is a highly variable process, it is necessary to obtain a synoptic data set covering a broad range of time-scales in order accurately to assess the status of any given TTS (Nguyen et al. 2009; Costigan et al. 2014). In order to capture this behaviour, we constructed our monitoring campaign to probe, roughly uniformly, a broad range of time-scales, from 1 d up to ~1 yr. The latter upper limit was selected roughly to match the dynamical (orbital) time-scale at a distance of 1 au from the central source. Persistent accretion (or absence thereof) over such a time-scale indicates that, even though the accretion flow may experience short-term fluctuations, the overall inward flow of material within that region remains stable (or absent) over dynamically long time-scales.

## 2.2 Sample selection

This survey is focused on the Taurus–Auriga star-forming region, arguably the best-studied population of TTS among nearby molecular clouds. An understanding of the frequency at which passive discs and objects with flickering accretion are present in that region will provide valuable insights for studies of more distant star-forming regions, where usually only single-epoch, low to medium spectral resolution studies are available.

Our sample selection started with the identification of objects with a confirmed circumstellar disc, which we achieved by a thorough literature search of Hα EW measurements. Based on this, we created the following three subsamples:

(1) *candidate passive disc objects* (nine targets), whose published Hα EW measurements fall below the standard accretion threshold defined by Barrado y Navascués & Martín (2003);

(2) *borderline objects* (seven targets), whose Hα EW is within 1 to 2 times this threshold;

(3) *a control sample* (15 targets) of accreting TTS with a strong Hα EW.

In addition to these 31 targets with a confirmed disc, we also observed two disc-less objects (UX Tau C and MHO 4) with a late spectral type in order to test the reliability of our Hα measurements. Indeed, in the case of weak emission lines superimposed on a continuum dominated by deep photospheric features, larger uncertainties are associated with these measurements owing to uncertainties in

estimating the level of continuum emission at our medium spectral resolution.

Each of the subsamples defined above is used to address a distinct question. The candidate passive discs are the most intriguing, and we wish to confirm the prima facie interpretation of their published properties as being non-accreting circumstellar discs. If this interpretation is confirmed, they would be in a unique state. Alternatively, it may be that newer spectroscopic measurements, particularly considering the *W*₁₀ quantity, lead to a re-evaluation of the objects. The borderline objects were selected in order to test the hypothesis that accretion may be flickering in objects with a relatively low accretion rate (although we note that a medium Hα EW does not necessarily imply a low accretion rate). Finally, the control sample was observed in order to understand the typical variability of ‘normal’ TTS over the time-scales and with the observational probes used in this study.

As shown in Fig. 1, most of our targets have near- and mid-infrared colours typical of full-fledged TTS discs. A few targets with a weak near-infrared ([$K$ − 8]) excess but a medium-to-strong mid-infrared ([$K$ − 24]) excess, generally classified as transition discs, are included in this survey. For a handful of targets, even though the *Spitzer* photometry is incomplete, Luhman et al. (2010) were able to classify the objects as ‘Class II’, with the exceptions of FW Tau and RX J0432+1735. For these two objects, a significant mid-infrared, far-infrared excess and/or millimetre emission from circumstellar dust has been confirmed (Andrews & Williams 2005; Wahhaj et al. 2010; Cieza et al. 2013; Howard et al. 2013). On the other hand, CZ Tau appears to have extremely red colours, more typical of an embedded Class I source (this source is discussed in Section 5.1).

We further note that the distribution of spectral types in our sample, from K0 to M6.5, is characteristic of the entire Taurus population (e.g. Luhman et al. 2006). Similarly, the ranges of visible brightness are similar for all three subsamples. Finally, as is typical for any sample of pre-main-sequence stars in Taurus, a significant fraction of our targets (12/33) are members of multiple systems, with separations ranging from 75 to 2000 au. Systems with a projected separation of less than ≈2 arcsec are liable to source confusion in our seeing-limited observations, and care must be taken when interpreting the system-integrated spectra obtained here (see Section 4).

As discussed above, the Hα line is not guaranteed to be a perfect tracer of accretion, so the W/C TTS classification can only be considered a first attempt at assessing the accretion status of our targets. Fortunately, the rich literature on the Taurus–Auriga star-forming region provides us with more discriminating observations, such as the presence of UV excess and/or veiling of photospheric lines across the visible range. We explored the results of UV excess searches (Muzerolle, Hartmann & Calvet 1998; White & Ghez 2001; Valenti, Fallon & Johns-Krull 2003; Ingleby et al. 2013), veiling in the blue optical (Valenti, Basri & Johns 1993) and veiling in the red optical (White & Basri 2003; Herczeg & Hillenbrand 2008, 2014) for all of our targets. If a target was found to have evidence for accretion in any of these observations, it is classified as an a priori accretor. In the absence of observations in the UV or blue optical, the veiling in the red optical is the only available element. However, because an absence of red veiling is sometimes found in UV-confirmed accretors, the classification based on red veiling alone is considered uncertain in the case of a non-detection. Finally, we note that MHO 5 is classified as a ‘possible accretor’ by Herczeg & Hillenbrand (2008); that is, its status remains uncertain.

The main properties of all sources monitored in this program are presented in Table 1.
<figure><img src="image_3.png" /><figcaption>**Figure 1.** Left: Hα equivalent width (EW) from the literature as a function of spectral type for the targets in our sample. The dashed and dotted lines represent the canonical threshold for separating accreting from non-accreting T Tauri stars (Barrado y Navascués & Martín 2003) and twice that value, respectively. Objects lying between those two lines are referred to as 'borderline' objects because they lie close to the threshold value, while those above the dotted line constitute our control sample of strongly accreting objects. Red squares and green circles indicate candidate passive discs and accreting objects, respectively. The two blue triangles are disc-less objects that we monitored to serve as a benchmark for non-accreting low-mass T Tauri stars. Right: Power-law indices to the mid-infrared part of the spectral energy distributions of members of the Taurus star-forming region, from Luhman et al. (2010): asterisks, plus signs and diamonds represent known Class III, II and I objects, respectively. The samples targeted in this study are indicated by filled green circles ('borderline' and control-sample targets), red squares (candidate passive discs) and blue triangles (disc-less targets). The grey horizontal band and vertical line mark the threshold for assessing the presence of significant infrared excess, as defined by Luhman et al. (2010). Five targets have incomplete *Spitzer* photometry and cannot be placed in this diagram. Their inclusion in our survey is discussed in Section 2.2.</figcaption></figure>

## 3 OBSERVATIONS AND DATA REDUCTION

The observations were gathered with the Calar Alto (CAHA) 3.5-m telescope, the 4.2-m William Herschel Telescope (WHT), the San Pedro Martir (SPM) 2.1-m telescope and the Lick Observatory Shane 3-m telescope, using their respective optical spectrographs. The gratings used for the observations and the resulting spectral resolution (as well as the $W_{10}$ measured on isolated lines in the spectra of arc lamps) are summarized in Table 2. The spectral resolution of the observations obtained with the WHT/ISIS R185R grating is too low to measure any intrinsic line width, and we only measure the EW of emission lines. Slit widths of 1 to 2 arcsec were used, depending primarily on seeing conditions. Except for the cases of close binaries, the slit was oriented along the paralactic angle in order to minimize the effects of differential atmospheric refraction.

Data were obtained during nine separate nights in autumn 2009, supplemented by a four-night run in autumn 2010 during which the most interesting objects were observed in order to achieve a 1-yr total-time baseline. The UX Tau A–C pair (2.7–arcsec separation) could only be resolved during the nights with the best seeing, resulting in poorer sampling for the faint secondary. Overall, our survey covers time-scales ranging from 1 to ~60 d for most targets, almost uniformly, in addition to the 1-yr longer baseline for the objects observed in autumn 2010. In some cases, multiple spectra of the same target were obtained consecutively in order to improve on-sky efficiency. However, because these spectra are always for bright targets with a high signal-to-noise ratio (SNR), we do not use them to probe the variability of time-scales ≲5 min; we only used these spectra to reject cosmic ray hits and uncorrected bad pixels.

The raw data products from all instruments used in this survey are very similar in their structure. We thus used the same data reduction pipeline to all data sets, with only minor adjustments. First, a bias frame was subtracted from the raw spectral frames before a flat-field correction (based on the spectrum of a broad spectral lamp

in the dome or within the calibration unit of the instrument) was applied. Second, the raw one-dimensional spectrum of the target was extracted from the two-dimensional frame using a fixed-width window centred on the position of the star at each pixel along the dispersion axis. An estimate of the sky background emission, determined using the median of adjacent pixels along the slit direction, was then subtracted, taking advantage of the fact that the spatial and spectral axes are nearly perpendicular for all spectrographs used in this study. The wavelength calibration was established using the spectra of arc lamps. In the case of the KAST spectrograph, both the flat-field correction and the wavelength calibration had to be conducted for every individual target in order to compensate for the effects of flexures, which are particularly large in the red arm of this instrument.

The spectra were then corrected for airmass using atmospheric absorption profiles appropriate for each observatory. This step is not aimed at fully suppressing all telluric absorption features but rather at removing the overall colour trend induced by the atmosphere, by bringing all spectra to a uniform airmass (of unity). Finally, atmospheric absorption features were estimated from the ratio of the observed to the absolute spectra of several early-type spectroscopic standards. While such an approach results, in principle, in an absolute spectrophotometric calibration, our observing strategy (e.g. fixed slit width throughout the night, despite sometimes varying seeing conditions; slit orientation not fixed to the parallactic angle), as well as the occasional presence of thin clouds, precluded such a calibration. Our program, which is focused on the width and EW of emission lines but not on their absolute luminosity, nor on the precise continuum shape of each spectrum, is insensitive to the approximative precision of this process. The final spectra usually achieve a high SNR in the vicinity of the Hα line, with 96, 90 and 80 percent of our spectra exceeding SNR = 50, 75 and 100 per resolution element, respectively (see Table 3). All spectra of 4 of our targets are presented in Fig. 2.
<table><caption>**Table 1.** Observed sample. Spectral types (Sp.T.) and spectral energy distribution (SED) class are adopted from Herczeg & Hillenbrand (2014) unless otherwise stated. The literature TTS classification is based on the strength of the Hα line relative to the spectral-type-dependent accretion threshold defined by Barrado y Navasués & Martín (2003). The presence of UV excess and/or optical veiling is assessed from the work of Valenti et al. (1993); Muzerolle et al. (1998); White & Ghez (2001); White & Basri (2003); Valenti et al. (2003); Herczeg & Hillenbrand (2008, 2014) and Ingleby et al. (2013). The multiplicity flag (Mult.) indicates single (S), binary (B), triple (T) and quadruple (Q) systems; only companions out to projected separations up to 2000 au are considered. N<sub>spec</sub> is the number of spectra obtained in this study, separated in time by a maximum of Δt<sub>max</sub>. References for Hα measurements: (1) Herbig & Bell (1988); (2) White & Ghez (2001); (3) Wahhaj et al. (2010); (4) Strom & Strom (1994); (5) Beckwith et al. (1990); (6) Briceño et al. (1998); (7) Hartigan, Strom & Strom (1994); (8) Nguyen et al. (2009). Individual notes: (a) Far-infrared and mm excess (Andrews & Williams 2005; Howard et al. 2013); (b) Wichmann et al. (1996); (c) 24 µm and 70 µm excess (Wahhaj et al. 2010; Cieza et al. 2013); (d) Luhman et al. (2010).</caption><thead><tr><th>Object</th><th>Sp.T.</th><th>R<br>[mag]</th><th>EW(Hα)<br>[Å]</th><th>Hα Ref.</th><th>TTS</th><th>Lit. classification<br>UV/veiling</th><th>SED</th><th>Accretor<br>in this survey</th><th>Mult.</th><th>N<sub>spec</sub></th><th>Δt<sub>max</sub><br>[d]</th></tr></thead><tbody><tr><td colspan="12" style="text-align:center; font-weight:bold;">Candidate passive discs</td></tr><tr><td>CoKu Tau 4</td><td>M1</td><td>14.48</td><td>-1.8</td><td>1</td><td>W</td><td>N?</td><td>II</td><td>N</td><td>B</td><td>11</td><td>372</td></tr><tr><td>CZ Tau</td><td>M4</td><td>14.77</td><td>-4.0</td><td>1</td><td>W</td><td>N</td><td>II</td><td>N?</td><td>B</td><td>11</td><td>373</td></tr><tr><td>FW Tau</td><td>M6</td><td>14.80</td><td>-11.6</td><td>2</td><td>W</td><td>N</td><td>II/III<sup>a</sup></td><td>N</td><td>T</td><td>11</td><td>372</td></tr><tr><td>HQ Tau</td><td>K2</td><td>11.18</td><td>-2</td><td>8</td><td>W</td><td>N?</td><td>II</td><td>Y</td><td>S</td><td>11</td><td>372</td></tr><tr><td>IQ Tau</td><td>M1</td><td>12.28</td><td>-7.7</td><td>1</td><td>W</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>8</td><td>60</td></tr><tr><td>RX J0432.8+1735</td><td>M2<sup>b</sup></td><td>...</td><td>-1.9</td><td>3</td><td>W</td><td>...</td><td>II<sup>c</sup></td><td>N</td><td>S</td><td>11</td><td>372</td></tr><tr><td>V410 Tau X-ray 6</td><td>M6</td><td>15.08</td><td>-9.2</td><td>4</td><td>W</td><td>...</td><td>II</td><td>N?</td><td>S</td><td>10</td><td>372</td></tr><tr><td>V819 Tau</td><td>K8</td><td>12.24</td><td>-1.7</td><td>1</td><td>W</td><td>Y</td><td>II</td><td>N</td><td>S</td><td>11</td><td>372</td></tr><tr><td>V836 Tau</td><td>M1</td><td>12.17</td><td>-9</td><td>1</td><td>W</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>11</td><td>373</td></tr><tr><td colspan="12" style="text-align:center; font-weight:bold;">Borderline objects</td></tr><tr><td>CX Tau</td><td>M2.5</td><td>12.65</td><td>-20</td><td>1</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>8</td><td>60</td></tr><tr><td>DN Tau</td><td>M0.5</td><td>11.49</td><td>-12</td><td>1</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>9</td><td>370</td></tr><tr><td>FN Tau</td><td>M3.5</td><td>14.68</td><td>-25</td><td>1</td><td>C</td><td>N</td><td>II</td><td>Y?</td><td>S</td><td>6</td><td>361</td></tr><tr><td>GH Tau</td><td>M2.5</td><td>11.77</td><td>-15</td><td>2</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>B</td><td>5</td><td>57</td></tr><tr><td>IP Tau</td><td>M0.5</td><td>12.46</td><td>-11</td><td>1</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>8</td><td>60</td></tr><tr><td>MHO 5</td><td>M6.5</td><td>16.23</td><td>-50</td><td>6</td><td>C</td><td>Y?</td><td>II</td><td>Y</td><td>S</td><td>10</td><td>373</td></tr><tr><td>V807 Tau</td><td>K7.5</td><td>10.07</td><td>-13</td><td>1</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>T</td><td>8</td><td>60</td></tr><tr><td colspan="12" style="text-align:center; font-weight:bold;">Control sample – Disc</td></tr><tr><td>BP Tau</td><td>M0.5</td><td>11.62</td><td>-40</td><td>4</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>8</td><td>60</td></tr><tr><td>CY Tau</td><td>M2.5</td><td>12.35</td><td>-70</td><td>1</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>8</td><td>60</td></tr><tr><td>DE Tau</td><td>M2.5</td><td>11.69</td><td>-54</td><td>4</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>8</td><td>60</td></tr><tr><td>DH Tau</td><td>M2.5</td><td>13.59</td><td>-53</td><td>1</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>B</td><td>7</td><td>369</td></tr><tr><td>DS Tau</td><td>M0.5</td><td>11.56</td><td>-59</td><td>1</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>8</td><td>60</td></tr><tr><td>FM Tau</td><td>M4.5</td><td>13.64</td><td>-62</td><td>7</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>9</td><td>370</td></tr><tr><td>FP Tau</td><td>M2.5</td><td>12.72</td><td>-38</td><td>1</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>8</td><td>60</td></tr><tr><td>FQ Tau</td><td>M4.5</td><td>13.68</td><td>-114</td><td>4</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>B</td><td>5</td><td>57</td></tr><tr><td>FY Tau</td><td>M0</td><td>14.17</td><td>-59</td><td>1</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>8</td><td>60</td></tr><tr><td>FZ Tau</td><td>M0.5</td><td>13.83</td><td>-204</td><td>1</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>4</td><td>57</td></tr><tr><td>GI Tau</td><td>M0.5</td><td>12.15</td><td>-20</td><td>7</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>T</td><td>8</td><td>60</td></tr><tr><td>GK Tau</td><td>K3</td><td>11.58</td><td>-22</td><td>7</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>T</td><td>8</td><td>60</td></tr><tr><td>LkCa 15</td><td>K5.5</td><td>11.61</td><td>-13</td><td>1</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>S</td><td>8</td><td>60</td></tr><tr><td>UX Tau A</td><td>K0</td><td>10.48</td><td>-9.5</td><td>2</td><td>C</td><td>Y</td><td>II</td><td>Y</td><td>Q</td><td>9</td><td>371</td></tr><tr><td>V710 Tau</td><td>M3.5</td><td>12.50</td><td>-48</td><td>1</td><td>C</td><td>N?</td><td>II</td><td>Y</td><td>B</td><td>8</td><td>370</td></tr><tr><td colspan="12" style="text-align:center; font-weight:bold;">Control sample – Disc-less</td></tr><tr><td>MHO 4</td><td>M7<sup>d</sup></td><td>16.36</td><td>-42</td><td>6</td><td>W</td><td>N?</td><td>III</td><td>Y?</td><td>S</td><td>11</td><td>373</td></tr><tr><td>UX Tau C</td><td>M3</td><td>15.11</td><td>-8.5</td><td>2</td><td>W</td><td>N?</td><td>III</td><td>N</td><td>Q</td><td>7</td><td>60</td></tr></tbody></table>

<table><caption>**Table 2.** Instrumental setup. W<sub>10</sub><sup>inst</sup> indicates the measured width at 10 per cent of the peak of isolated emission lines around the wavelength of the Hα line from the spectra of calibration (arc) lamps.</caption><thead><tr><th>Telescope</th><th>Instrum. + Grating</th><th>Bandpass [Å]</th><th>Sampling [Å]</th><th>R</th><th>W<sub>10</sub><sup>inst</sup> [km s<sup>-1</sup>]</th><th>Obs. date</th></tr></thead><tbody><tr><td>CAHA 3.5 m</td><td>TWIN + T06</td><td>5870–7030</td><td>0.55</td><td>4860</td><td>135 ± 5</td><td>2009/10/27</td></tr><tr><td>CAHA 3.5 m</td><td>TWIN + T07</td><td>5870–9100</td><td>1.64</td><td>2020</td><td>335 ± 10</td><td>2009/11/23, 2009/12/10</td></tr><tr><td>WHT</td><td>ISIS + R600R</td><td>5720–7800</td><td>0.49</td><td>4560</td><td>125 ± 5</td><td>2009/10/30–31, 2009/12/26</td></tr><tr><td>WHT</td><td>ISIS + R158R</td><td>4780–9700</td><td>1.82</td><td>400</td><td>900 ± 30</td><td>2009/11/07</td></tr><tr><td>SPM 2.1 m</td><td>Boller&Chivens</td><td>5400–7600</td><td>2.07</td><td>1780</td><td>360 ± 5</td><td>2009/12/02–03</td></tr><tr><td>Lick 3 m</td><td>KAST + #4</td><td>5800–7200</td><td>1.18</td><td>2770</td><td>260 ± 10</td><td>2010/11/11–14</td></tr></tbody></table>
<table><caption>**Table 3.** Spectral line measurements. The last line for each object provides the average and standard deviation of all H α EW and W$_{10}$ measurements (or the median upper limit on W$_{10}$ in the case of objects for which most spectra did not yield a detection), as well as the average and standard deviation of the mean for all detections of the Li 6707 absorption line. The signal-to-noise ratio (SNR) listed in the third column is estimated in the 6400–6700 Å range and is reported on a per resolution element basis. The 'accretor' status (14th column) is explained in Section 4.5.</caption><thead><tr><th>Target</th><th>Date</th><th>SNR</th><th>EW(Hα) [Å]</th><th>W<sub>10</sub> [km s<sup>-1</sup>]</th><th>Asym. profile</th><th>He: 15876</th><th>[O I] 6300</th><th>Other emission line EWs [Å]</th><th>He: 6678</th><th>Ca 8498</th><th>Ca 8542</th><th>Ca 8662</th><th>Li 6707 EW [Å]</th><th>Accretor</th></tr></thead><tbody><tr><td rowspan="10">CoKu Tau 4</td><td>2009 Oct 27</td><td>117</td><td>1.4<sup>+0.1</sup><sub>-0.2</sub></td><td>138<sup>+49</sup><sub>-48</sub></td><td>N</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.59 ± 0.05</td><td>N</td></tr><tr><td>2009 Oct 30</td><td>138</td><td>0.9<sup>+0.2</sup><sub>-0.1</sub></td><td>&lt;125</td><td>N</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.57 ± 0.05</td><td>N</td></tr><tr><td>2009 Oct 31</td><td>213</td><td>0.9<sup>+0.1</sup><sub>-0.2</sub></td><td>&lt;125</td><td>N</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.58 ± 0.05</td><td>N</td></tr><tr><td>2009 Nov 07</td><td>261</td><td>1.0 ± 0.2</td><td>...</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>N</td></tr><tr><td>2009 Nov 23</td><td>157</td><td>0.8 ± 0.2</td><td>&lt;200</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.48 ± 0.10</td><td>N</td></tr><tr><td>2009 Dec 03</td><td>76</td><td>0.8<sup>+0.1</sup><sub>-0.2</sub></td><td>&lt;200</td><td>N</td><td>≥ -0.45</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.50 ± 0.15</td><td>N</td></tr><tr><td>2009 Dec 10</td><td>153</td><td>0.9 ± 0.1</td><td>&lt;200</td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.41 ± 0.10</td><td>N</td></tr><tr><td>2009 Dec 26</td><td>105</td><td>1.1 ± 0.1</td><td>158<sup>+49</sup><sub>-48</sub></td><td>N</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.62 ± 0.05</td><td>N</td></tr><tr><td>2010 Nov 11</td><td>126</td><td>1.1 ± 0.1</td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.55 ± 0.10</td><td>N</td></tr><tr><td>2010 Nov 12</td><td>172</td><td>1.1 ± 0.1</td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.40 ± 0.10</td><td>N</td></tr><tr><td>2010 Nov 13</td><td>205</td><td>1.3<sup>+0.2</sup><sub>-0.1</sub></td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.48 ± 0.10</td><td>N</td></tr><tr><td colspan="2">Weighted average</td><td>1.0 ± 0.2</td><td>&lt;175</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.56 ± 0.02</td><td>N</td></tr><tr><td rowspan="10">CZ Tau</td><td>2009 Oct 27</td><td>107</td><td>5.4<sup>+0.1</sup><sub>-0.2</sub></td><td>&lt;125</td><td>N</td><td>...</td><td>-0.27 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.26 ± 0.05</td><td>N?</td></tr><tr><td>2009 Oct 30</td><td>102</td><td>4.7 ± 0.1</td><td>&lt;125</td><td>N</td><td>≥ -0.15</td><td>-0.16 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.37 ± 0.05</td><td>N?</td></tr><tr><td>2009 Oct 31</td><td>141</td><td>4.2 ± 0.1</td><td>&lt;125</td><td>N</td><td>≥ -0.15</td><td>-0.44 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.38 ± 0.05</td><td>N?</td></tr><tr><td>2009 Nov 07</td><td>99</td><td>2.6<sup>+0.2</sup><sub>-0.1</sub></td><td>...</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>N</td></tr><tr><td>2009 Nov 23</td><td>108</td><td>5.2 ± 0.3</td><td>&lt;200</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≤ 0.30</td><td>N</td></tr><tr><td>2009 Dec 03</td><td>56</td><td>3.5<sup>+0.1</sup><sub>-0.3</sub></td><td>&lt;200</td><td>N</td><td>≥ -0.45</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>N</td></tr><tr><td>2009 Dec 10</td><td>184</td><td>4.0<sup>+0.1</sup><sub>-0.3</sub></td><td>&lt;200</td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≤ 0.30</td><td>N</td></tr><tr><td>2009 Dec 26</td><td>94</td><td>4.5 ± 0.1</td><td>&lt;125</td><td>N</td><td>...</td><td>-1.50 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.29 ± 0.05</td><td>N?</td></tr><tr><td>2010 Nov 11</td><td>126</td><td>4.2<sup>+0.4</sup><sub>-0.1</sub></td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.42 ± 0.10</td><td>N</td></tr><tr><td>2010 Nov 12</td><td>107</td><td>3.8<sup>+0.4</sup><sub>-0.1</sub></td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>-0.48 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.40 ± 0.10</td><td>N?</td></tr><tr><td>2010 Nov 14</td><td>93</td><td>3.9<sup>+0.2</sup><sub>-0.1</sub></td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>-0.47 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.36 ± 0.10</td><td>N?</td></tr><tr><td colspan="2">Weighted average</td><td>4.2 ± 0.9</td><td>&lt;175</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.34 ± 0.02</td><td>N?</td></tr><tr><td rowspan="10">FW Tau</td><td>2009 Oct 27</td><td>109</td><td>17.7 ± 0.5</td><td>141<sup>+24</sup><sub>-25</sub></td><td>N</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.49 ± 0.05</td><td>N</td></tr><tr><td>2009 Oct 30</td><td>132</td><td>12.5<sup>+0.2</sup><sub>-0.5</sub></td><td>&lt;125</td><td>N</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.35 ± 0.05</td><td>N</td></tr><tr><td>2009 Oct 31</td><td>143</td><td>13.6<sup>+0.1</sup><sub>-0.3</sub></td><td>&lt;125</td><td>N</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.41 ± 0.05</td><td>N</td></tr><tr><td>2009 Nov 07</td><td>55</td><td>15.4<sup>+0.3</sup><sub>-0.4</sub></td><td>...</td><td>...</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≤ 0.90</td><td>N</td></tr><tr><td>2009 Nov 23</td><td>157</td><td>15.6 ± 0.5</td><td>&lt;200</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.36 ± 0.10</td><td>N</td></tr><tr><td>2009 Dec 03</td><td>55</td><td>13.1<sup>+0.2</sup><sub>-0.4</sub></td><td>&lt;200</td><td>N</td><td>≥ -0.45</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>N</td></tr><tr><td>2009 Dec 10</td><td>197</td><td>11.7 ± 0.5</td><td>&lt;200</td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.33 ± 0.10</td><td>N</td></tr><tr><td>2009 Dec 26</td><td>83</td><td>12.3<sup>+0.2</sup><sub>-0.5</sub></td><td>156 ± 25</td><td>N</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.39 ± 0.05</td><td>N</td></tr><tr><td>2010 Nov 11</td><td>96</td><td>13.3 ± 1.0</td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.45 ± 0.10</td><td>N</td></tr><tr><td>2010 Nov 12</td><td>142</td><td>13.0 ± 1.0</td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.35 ± 0.10</td><td>N</td></tr><tr><td>2010 Nov 13</td><td>99</td><td>10.7 ± 1.0</td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.53 ± 0.10</td><td>N</td></tr></tbody></table>
<table><caption>Table 3 – continued</caption><thead><tr><th>Target</th><th>Date</th><th>SNR</th><th>EW(Hα) [Å]</th><th>W<sub>10</sub> [km s<sup>-1</sup>]</th><th>Asym. profile</th><th>He<sub>1</sub> 5876</th><th>[O I] 6300</th><th>Other emission line EWs [Å]<br>He<sub>1</sub> 6678<br>Ca 8498</th><th>Ca 8542</th><th>Ca 8662</th><th>Li 6707 EW [Å]</th><th>Accretor</th></tr></thead><tbody><tr><td rowspan="12">HQ Tau</td><td colspan="12">Weighted average</td></tr><tr><td>2009 Oct 27</td><td>240</td><td>13.5 ± 2.1</td><td>&lt;175</td><td>Y</td><td>...</td><td>≥ −0.15</td><td>≥ −0.15</td><td>...</td><td>...</td><td>0.41 ± 0.02</td><td>N</td></tr><tr><td>2009 Oct 30</td><td>345</td><td>3.3 ± 0.1</td><td>545 ± 29</td><td>Y</td><td>≥ −0.15</td><td>≥ −0.15</td><td>≥ −0.15</td><td>...</td><td>...</td><td>0.25 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>230</td><td>1.6 ± 0.1</td><td>522<sup>+29</sup><sub>−34</sub></td><td>Y</td><td>≥ −0.15</td><td>≥ −0.15</td><td>≥ −0.15</td><td>...</td><td>...</td><td>0.30 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>353</td><td>2.7<sup>+0.1</sup><sub>−0.3</sub></td><td>...</td><td>Y</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≥ 0.60</td><td>Y?</td></tr><tr><td>2009 Nov 23</td><td>139</td><td>2.7<sup>+0.1</sup><sub>−0.3</sub></td><td>370<sup>+45</sup><sub>−52</sub></td><td>N</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≤ 0.30</td><td>Y?</td></tr><tr><td>2009 Dec 03</td><td>85</td><td>4.9<sup>+0.1</sup><sub>−0.2</sub></td><td>494<sup>+43</sup><sub>−49</sub></td><td>N</td><td>≥ −0.45</td><td>≥ −0.45</td><td>≥ −0.45</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y?</td></tr><tr><td>2009 Dec 10</td><td>132</td><td>2.2<sup>+0.1</sup><sub>−0.2</sub></td><td>324<sup>+47</sup><sub>−51</sub></td><td>N</td><td>...</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≤ 0.30</td><td>Y?</td></tr><tr><td>2009 Dec 26</td><td>136</td><td>2.5 ± 0.1</td><td>496<sup>+29</sup><sub>−31</sub></td><td>Y</td><td>...</td><td>≥ −0.15</td><td>≥ −0.15</td><td>...</td><td>...</td><td>0.29 ± 0.05</td><td>Y</td></tr><tr><td>2010 Nov 11</td><td>162</td><td>4.3<sup>+0.1</sup><sub>−0.2</sub></td><td>468<sup>+37</sup><sub>−41</sub></td><td>Y</td><td>≥ −0.30</td><td>−0.31 ± 0.10</td><td>≥ −0.30</td><td>...</td><td>...</td><td>0.34 ± 0.10</td><td>Y</td></tr><tr><td>2010 Nov 12</td><td>197</td><td>4.1<sup>+0.1</sup><sub>−0.2</sub></td><td>416<sup>+37</sup><sub>−41</sub></td><td>Y</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>...</td><td>...</td><td>0.30 ± 0.10</td><td>Y</td></tr><tr><td>2010 Nov 13</td><td>171</td><td>4.2<sup>+0.1</sup><sub>−0.3</sub></td><td>395<sup>+37</sup><sub>−40</sub></td><td>Y</td><td>≥ −0.30</td><td>−0.48 ± 0.10</td><td>≥ −0.30</td><td>...</td><td>...</td><td>≤ 0.30</td><td>Y</td></tr><tr><td colspan="12">Weighted average</td></tr><tr><td rowspan="12">IQ Tau</td><td>2009 Oct 27</td><td>86</td><td>11.6<sup>+0.4</sup><sub>−0.6</sub></td><td>373<sup>+14</sup><sub>−15</sub></td><td>Y</td><td>...</td><td>−1.31 ± 0.05</td><td>−0.22 ± 0.05</td><td>...</td><td>...</td><td>0.54 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>143</td><td>8.7<sup>+0.1</sup><sub>−0.3</sub></td><td>386<sup>+12</sup><sub>−14</sub></td><td>Y</td><td>≥ −0.15</td><td>−1.21 ± 0.05</td><td>≥ −0.15</td><td>...</td><td>...</td><td>0.55 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>210</td><td>10.5<sup>+0.5</sup><sub>−0.6</sub></td><td>368<sup>+14</sup><sub>−15</sub></td><td>Y</td><td>−0.23 ± 0.05</td><td>−1.30 ± 0.05</td><td>≥ −0.15</td><td>...</td><td>...</td><td>0.57 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>307</td><td>12.0<sup>+0.4</sup><sub>−0.4</sub></td><td>...</td><td>...</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≤ 0.60</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>218</td><td>42.9 ± 4.0</td><td>555<sup>+20</sup><sub>−27</sub></td><td>N</td><td>−2.34 ± 0.10</td><td>−1.53 ± 0.10</td><td>≥ −0.30</td><td>−3.65 ± 0.10</td><td>−3.35 ± 0.10</td><td>−2.88 ± 0.10</td><td>0.33 ± 0.10</td></tr><tr><td>2009 Dec 02</td><td>88</td><td>24.5<sup>+0.1</sup><sub>−0.6</sub></td><td>411 ± 19</td><td>N</td><td>−3.13 ± 0.15</td><td>−0.64 ± 0.15</td><td>≥ −0.45</td><td>...</td><td>...</td><td>0.48 ± 0.15</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>269</td><td>19.3<sup>+0.3</sup><sub>−0.2</sub></td><td>618<sup>+19</sup><sub>−27</sub></td><td>N</td><td>...</td><td>−0.45 ± 0.10</td><td>−0.50 ± 0.10</td><td>−4.80 ± 0.10</td><td>−5.34 ± 0.10</td><td>−4.35 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>92</td><td>9.5<sup>+0.6</sup></td><td>419<sup>+14</sup><sub>−13</sub></td><td>Y</td><td>...</td><td>−1.27 ± 0.05</td><td>−0.16 ± 0.05</td><td>...</td><td>...</td><td>0.54 ± 0.05</td><td>Y</td></tr><tr><td colspan="12">Weighted average</td></tr><tr><td rowspan="12">RX J0432+1735</td><td>2009 Oct 27</td><td>120</td><td>1.6<sup>+0.1</sup><sub>−0.2</sub></td><td>&lt;125</td><td>N</td><td>...</td><td>≥ −0.15</td><td>≥ −0.15</td><td>...</td><td>...</td><td>0.66 ± 0.05</td><td>N</td></tr><tr><td>2009 Oct 30</td><td>140</td><td>1.2 ± 0.1</td><td>&lt;125</td><td>N</td><td>≥ −0.15</td><td>≥ −0.15</td><td>≥ −0.15</td><td>...</td><td>...</td><td>0.62 ± 0.05</td><td>N</td></tr><tr><td>2009 Oct 31</td><td>129</td><td>1.4<sup>+0.1</sup><sub>−0.3</sub></td><td>&lt;125</td><td>N</td><td>≥ −0.15</td><td>≥ −0.15</td><td>≥ −0.15</td><td>...</td><td>...</td><td>0.65 ± 0.05</td><td>N</td></tr><tr><td>2009 Nov 07</td><td>175</td><td>1.1 ± 0.1</td><td>...</td><td>...</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≥ −0.60</td><td>≤ 0.60</td><td>N</td></tr><tr><td>2009 Nov 23</td><td>120</td><td>1.3 ± 0.1</td><td>&lt;200</td><td>N</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>0.51 ± 0.10</td><td>N</td></tr><tr><td>2009 Dec 03</td><td>58</td><td>1.4 ± 0.1</td><td>&lt;200</td><td>N</td><td>≥ −0.45</td><td>≥ −0.45</td><td>≥ −0.45</td><td>...</td><td>...</td><td>0.47 ± 0.15</td><td>N</td></tr><tr><td>2009 Dec 10</td><td>148</td><td>1.3<sup>+0.1</sup><sub>−0.2</sub></td><td>&lt;200</td><td>N</td><td>...</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>0.42 ± 0.10</td></tr><tr><td>2009 Dec 26</td><td>90</td><td>1.4 ± 0.1</td><td>&lt;125</td><td>N</td><td>...</td><td>≥ −0.15</td><td>≥ −0.15</td><td>...</td><td>...</td><td>0.64 ± 0.05</td><td>N</td></tr><tr><td>2010 Nov 11</td><td>147</td><td>1.6<sup>+0.1</sup><sub>−0.3</sub></td><td>&lt;175</td><td>N</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>...</td><td>...</td><td>0.57 ± 0.10</td><td>N</td></tr><tr><td>2010 Nov 12</td><td>144</td><td>1.7 ± 0.1</td><td>&lt;175</td><td>N</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>...</td><td>...</td><td>0.48 ± 0.10</td><td>N</td></tr><tr><td>2010 Nov 13</td><td>173</td><td>1.6 ± 0.1</td><td>&lt;175</td><td>N</td><td>≥ −0.30</td><td>≥ −0.30</td><td>≥ −0.30</td><td>...</td><td>...</td><td>0.48 ± 0.10</td><td>N</td></tr><tr><td colspan="12">Weighted average</td></tr><tr><td></td><td></td><td></td><td>1.6 ± 0.2</td><td>&lt;175</td><td></td><td></td><td></td><td></td><td></td><td>0.60 ± 0.02</td><td>N</td></tr></tbody></table>
<table><caption>Table 3 – continued</caption><thead><tr><th>Target</th><th>Date</th><th>SNR</th><th>EW(H α) [Å]</th><th>W<sub>10</sub> [km s<sup>-1</sup>]</th><th>Asym. profile</th><th>He<sub>1</sub> 5876</th><th>Other emission line EWs [Å]<br>[OⅠ] 6300</th><th>He<sub>1</sub> 6678</th><th>Ca 8498</th><th>Ca 8542</th><th>Ca 8662</th><th>Li 6707 EW [Å]</th><th>Accretor</th></tr></thead><tbody><tr><td rowspan="10">V410 Tau X-ray 6</td><td>2009 Oct 27</td><td>57</td><td>7.8<sup>+0.1</sup><sub>-0.2</sub></td><td>&lt;125</td><td>N</td><td>...</td><td>-0.57 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.25 ± 0.05</td><td>N?</td></tr><tr><td>2009 Oct 30</td><td>73</td><td>7.1<sup>+0.1</sup><sub>-0.2</sub></td><td>&lt;125</td><td>N</td><td>≥ -0.15</td><td>-0.52 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.32 ± 0.05</td><td>N?</td></tr><tr><td>2009 Oct 31</td><td>79</td><td>7.4<sup>+0.3</sup><sub>-0.3</sub></td><td>127<sup>+26</sup><sub>-28</sub></td><td>N</td><td>≥ -0.15</td><td>-0.90 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.37 ± 0.05</td><td>N?</td></tr><tr><td>2009 Nov 07</td><td>58</td><td>6.9 ± 0.3</td><td>...</td><td>...</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≤ 0.90</td><td>N</td><td>N</td></tr><tr><td>2009 Nov 23</td><td>179</td><td>7.0<sup>+0.2</sup><sub>-0.3</sub></td><td>&lt;200</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≤ 0.30</td><td>N</td><td>N</td></tr><tr><td>2009 Dec 10</td><td>169</td><td>6.5<sup>+0.2</sup><sub>-0.4</sub></td><td>&lt;200</td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≤ 0.30</td><td>N</td></tr><tr><td>2009 Dec 26</td><td>60</td><td>9.5<sup>+0.1</sup><sub>-0.2</sub></td><td>125<sup>+25</sup><sub>-26</sub></td><td>N</td><td>...</td><td>-0.88 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.29 ± 0.05</td><td>N?</td></tr><tr><td>2010 Nov 11</td><td>64</td><td>6.9 ± 0.3</td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>-1.55 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.30 ± 0.10</td><td>N?</td></tr><tr><td>2010 Nov 12</td><td>84</td><td>7.4 ± 0.2</td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>-0.95 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.35 ± 0.10</td><td>N?</td></tr><tr><td>2010 Nov 13</td><td>33</td><td>7.5 ± 0.5</td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>-1.65 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.36 ± 0.10</td><td>N?</td></tr><tr><td colspan="2">Weighted average</td><td>7.4 ± 0.8</td><td>&lt;175</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.31 ± 0.02</td><td>N?</td></tr><tr><td rowspan="10">V819 Tau</td><td>2009 Oct 27</td><td>111</td><td>2.0 ± 0.1</td><td>141 ± 39</td><td>N</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.56 ± 0.05</td><td>N</td></tr><tr><td>2009 Oct 30</td><td>161</td><td>1.8<sup>+0.1</sup><sub>-0.2</sub></td><td>146<sup>+38</sup><sub>-41</sub></td><td>N</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.54 ± 0.05</td><td>N</td></tr><tr><td>2009 Oct 31</td><td>181</td><td>1.1 ± 0.1</td><td>&lt;125</td><td>N</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.56 ± 0.05</td><td>N</td></tr><tr><td>2009 Nov 07</td><td>317</td><td>1.5 ± 0.1</td><td>...</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>N</td></tr><tr><td>2009 Nov 23</td><td>139</td><td>1.3 ± 0.1</td><td>&lt;200</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.53 ± 0.10</td><td>N</td></tr><tr><td>2009 Dec 02</td><td>89</td><td>1.5 ± 0.1</td><td>&lt;200</td><td>N</td><td>≥ -0.45</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>0.47 ± 0.15</td><td>N</td></tr><tr><td>2009 Dec 10</td><td>134</td><td>1.5 ± 0.1</td><td>&lt;200</td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.48 ± 0.10</td><td>N</td></tr><tr><td>2009 Dec 26</td><td>144</td><td>1.4 ± 0.1</td><td>&lt;125</td><td>N</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.56 ± 0.05</td><td>N</td></tr><tr><td>2010 Nov 11</td><td>115</td><td>1.5 ± 0.1</td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.45 ± 0.10</td><td>N</td></tr><tr><td>2010 Nov 12</td><td>116</td><td>1.2 ± 0.1</td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.41 ± 0.10</td><td>N</td></tr><tr><td>2010 Nov 13</td><td>139</td><td>1.4 ± 0.1</td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.44 ± 0.10</td><td>N</td></tr><tr><td colspan="2">Weighted average</td><td>1.5 ± 0.3</td><td>&lt;175</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.53 ± 0.02</td><td>N</td></tr><tr><td rowspan="10">V836 Tau</td><td>2009 Oct 27</td><td>131</td><td>17.9<sup>+0.4</sup><sub>-0.3</sub></td><td>278 ± 13</td><td>N</td><td>...</td><td>-0.52 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.57 ± 0.05</td><td>Y?</td></tr><tr><td>2009 Oct 30</td><td>168</td><td>20.8<sup>+0.5</sup><sub>-0.5</sub></td><td>279<sup>+12</sup><sub>-13</sub></td><td>N</td><td>-0.44 ± 0.05</td><td>-0.48 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.56 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>157</td><td>75.3<sup>+1.0</sup><sub>-3.5</sub></td><td>387<sup>+12</sup><sub>-14</sub></td><td>Y</td><td>-1.91 ± 0.05</td><td>-0.85 ± 0.05</td><td>-0.40 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.46 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>333</td><td>24.9<sup>+0.2</sup><sub>-1.1</sub></td><td>...</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>Y?</td></tr><tr><td>2009 Nov 23</td><td>147</td><td>33.7<sup>+0.5</sup><sub>-1.5</sub></td><td>356<sup>+21</sup><sub>-25</sub></td><td>N</td><td>-1.34 ± 0.10</td><td>-0.50 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.33 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>64</td><td>20.9<sup>+0.3</sup><sub>-0.7</sub></td><td>329<sup>+20</sup><sub>-24</sub></td><td>N</td><td>-1.13 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>0.50 ± 0.15</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>176</td><td>27.3<sup>+0.2</sup><sub>-0.3</sub></td><td>354<sup>+20</sup><sub>-21</sub></td><td>N</td><td>...</td><td>-0.57 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.31 ± 0.10</td><td>Y?</td></tr><tr><td>2009 Dec 26</td><td>102</td><td>29.8<sup>+0.7</sup><sub>-0.2</sub></td><td>334<sup>+21</sup><sub>-13</sub></td><td>N</td><td>...</td><td>-0.79 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.47 ± 0.05</td><td>Y?</td></tr><tr><td>2010 Nov 12</td><td>168</td><td>19.3<sup>+0.1</sup><sub>-0.4</sub></td><td>269<sup>+18</sup><sub>-19</sub></td><td>N</td><td>≥ -0.30</td><td>-0.44 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.38 ± 0.10</td><td>Y?</td></tr><tr><td>2010 Nov 13</td><td>137</td><td>25.8<sup>+0.4</sup><sub>-0.9</sub></td><td>308<sup>+18</sup><sub>-19</sub></td><td>N</td><td>≥ -0.30</td><td>-0.33 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.44 ± 0.10</td><td>Y?</td></tr><tr><td>2010 Nov 14</td><td>116</td><td>22.0<sup>+0.2</sup><sub>-0.4</sub></td><td>218 ± 19</td><td>N</td><td>-0.45 ± 0.10</td><td>-1.13 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.43 ± 0.10</td><td>Y</td></tr><tr><td colspan="2">Weighted average</td><td>28.9 ± 17.2</td><td>312 ± 51</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.48 ± 0.02</td><td>Y</td></tr></tbody></table>
<table><caption>Table 3 – continued</caption><thead><tr><th>Target</th><th>Date</th><th>SNR</th><th>EW(Hα) [Å]</th><th>W<sub>10</sub> [km s<sup>-1</sup>]</th><th>Asym. profile</th><th>He<sub>1</sub> 5876</th><th>Other emission line EWs [Å]<br>[OⅠ] 6300</th><th>He<sub>1</sub> 6678</th><th>Ca 8498</th><th>Ca 8542</th><th>Ca 8662</th><th>Li 6707 EW [Å]</th><th>Accretor</th></tr></thead><tbody><tr><td rowspan="10">CX Tau</td><td>2009 Oct 27</td><td>162</td><td>5.4 ± 0.1</td><td>324<sup>+17</sup><sub>-18</sub></td><td>Y</td><td>...</td><td>-0.21 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.47 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>131</td><td>4.0 ± 0.1</td><td>410<sup>+16</sup><sub>-16</sub></td><td>Y</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.60 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>204</td><td>5.1 ± 0.1</td><td>335 ± 16</td><td>Y</td><td>≥ -0.15</td><td>-0.21 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.62 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>150</td><td>5.7 ± 0.1</td><td>...</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>228</td><td>6.2 ± 0.3</td><td>341 ± 26</td><td>Y</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.36 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 02</td><td>119</td><td>11.1<sup>+0.2</sup><sub>-0.3</sub></td><td>419<sup>+30</sup><sub>-34</sub></td><td>N</td><td>≥ -0.45</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>0.53 ± 0.15</td><td>Y?</td></tr><tr><td>2009 Dec 10</td><td>161</td><td>10.6 ± 0.2</td><td>451<sup>+25</sup><sub>-27</sub></td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.40 ± 0.10</td><td>Y?</td></tr><tr><td>2009 Dec 26</td><td>136</td><td>9.2 ± 0.1</td><td>467<sup>+16</sup><sub>-19</sub></td><td>Y</td><td>...</td><td>-0.22 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.58 ± 0.05</td><td>Y</td></tr><tr><td colspan="13">Weighted average</td></tr><tr><td rowspan="10">DN Tau</td><td>2009 Oct 27</td><td>169</td><td>7.8<sup>+0.2</sup><sub>-0.1</sub></td><td>177<sup>+16</sup><sub>-13</sub></td><td>N</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.59 ± 0.05</td><td>Y?</td></tr><tr><td>2009 Oct 30</td><td>250</td><td>9.4 ± 0.1</td><td>216<sup>+15</sup><sub>-13</sub></td><td>N</td><td>-0.38 ± 0.05</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.54 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>233</td><td>8.6<sup>+0.1</sup><sub>-0.2</sub></td><td>232<sup>+14</sup><sub>-15</sub></td><td>N</td><td>-0.28 ± 0.05</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.57 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>276</td><td>8.8<sup>+0.4</sup><sub>-0.2</sub></td><td>...</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>Y?</td></tr><tr><td>2009 Nov 23</td><td>122</td><td>8.5 ± 0.1</td><td>226 ± 24</td><td>N</td><td>-0.88 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.48 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>174</td><td>11.1 ± 0.1</td><td>&lt;200</td><td>N</td><td>-0.72 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>0.45 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>159</td><td>7.4<sup>+0.1</sup><sub>-0.2</sub></td><td>213<sup>+24</sup><sub>-28</sub></td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.42 ± 0.10</td><td>Y?</td></tr><tr><td>2009 Dec 26</td><td>196</td><td>9.4 ± 0.1</td><td>236<sup>+16</sup><sub>-14</sub></td><td>N</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.51 ± 0.05</td><td>Y?</td></tr><tr><td>2010 Nov 11</td><td>172</td><td>11.9 ± 0.1</td><td>&lt;175</td><td>N</td><td>-0.75 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.48 ± 0.10</td><td>Y</td></tr><tr><td colspan="13">Weighted average</td></tr><tr><td rowspan="10">FN Tau</td><td>2009 Nov 07</td><td>108</td><td>17.5 ± 0.1</td><td>216 ± 21</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>Y?</td></tr><tr><td>2009 Dec 02</td><td>60</td><td>14.1<sup>+0.4</sup><sub>-0.4</sub></td><td>&lt;200</td><td>N</td><td>-0.60 ± 0.15</td><td>-0.71 ± 0.15</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>144</td><td>27.2<sup>+0.2</sup><sub>-0.3</sub></td><td>188 ± 17</td><td>N</td><td>...</td><td>-1.37 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.51 ± 0.05</td><td>Y?</td></tr><tr><td>2010 Nov 11</td><td>102</td><td>15.7 ± 0.1</td><td>&lt;175</td><td>N</td><td>-0.52 ± 0.10</td><td>-0.88 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.41 ± 0.10</td><td>Y</td></tr><tr><td>2010 Nov 12</td><td>129</td><td>16.9 ± 0.1</td><td>&lt;175</td><td>N</td><td>-0.43 ± 0.10</td><td>-1.07 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.60 ± 0.10</td><td>Y</td></tr><tr><td>2010 Nov 13</td><td>167</td><td>15.0 ± 0.1</td><td>&lt;175</td><td>N</td><td>-0.35 ± 0.10</td><td>-0.74 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.40 ± 0.10</td><td>Y</td></tr><tr><td colspan="13">Weighted average</td></tr><tr><td rowspan="10">GH Tau</td><td>2009 Oct 30</td><td>136</td><td>16.7<sup>+0.8</sup><sub>-0.3</sub></td><td>449<sup>+17</sup><sub>-16</sub></td><td>Y</td><td>-0.22 ± 0.05</td><td>-0.21 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.57 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>223</td><td>11.0<sup>+0.4</sup><sub>-0.4</sub></td><td>450<sup>+15</sup><sub>-16</sub></td><td>Y</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.58 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>158</td><td>21.8 ± 0.1</td><td>...</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>Y?</td></tr><tr><td>2009 Dec 03</td><td>90</td><td>16.7<sup>+0.1</sup><sub>-0.3</sub></td><td>530<sup>+21</sup><sub>-22</sub></td><td>N</td><td>≥ -0.45</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>124</td><td>16.2<sup>+0.4</sup><sub>-0.7</sub></td><td>477<sup>+14</sup><sub>-16</sub></td><td>Y</td><td>...</td><td>-0.35 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.47 ± 0.05</td><td>Y</td></tr><tr><td colspan="13">Weighted average</td></tr><tr><td></td><td></td><td>16.5 ± 3.8</td><td>&lt;175</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.54 ± 0.03</td><td>Y</td></tr></tbody></table>
<table><caption>Table 3 – continued</caption><thead><tr><th>Target</th><th>Date</th><th>SNR</th><th>EW(Hα) [Å]</th><th>W<sub>10</sub> [km s<sup>-1</sup>]</th><th>Asym. profile</th><th>He I 5876</th><th>[O] 6300</th><th>Other emission line EWs [Å]</th><th>He I 6678</th><th>Ca 8498</th><th>Ca 8542</th><th>Ca 8662</th><th>Li 6707 EW [Å]</th><th>Accretor</th></tr></thead><tbody><tr><td rowspan="10">IP Tau</td><td>2009 Oct 27</td><td>106</td><td>12.9<sup>+0.1</sup><sub>-0.6</sub></td><td>297<sup>+12</sup><sub>-15</sub></td><td>N</td><td>...</td><td>-0.31 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.53 ± 0.05</td><td>Y?</td></tr><tr><td>2009 Oct 30</td><td>189</td><td>14.7<sup>+0.3</sup><sub>-0.5</sub></td><td>292<sup>+12</sup><sub>-16</sub></td><td>N</td><td>-0.67 ± 0.05</td><td>-0.32 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.46 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>170</td><td>13.4<sup>+0.4</sup><sub>-0.4</sub></td><td>413 ± 13</td><td>Y</td><td>-0.33 ± 0.05</td><td>-0.19 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.45 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>290</td><td>15.3<sup>+0.3</sup><sub>-0.3</sub></td><td>...</td><td>Y</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>Y?</td></tr><tr><td>2009 Nov 23</td><td>130</td><td>12.1<sup>+0.2</sup><sub>-0.6</sub></td><td>380<sup>+21</sup><sub>-32</sub></td><td>N</td><td>-0.31 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.41 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>89</td><td>13.3<sup>+0.4</sup><sub>-0.8</sub></td><td>414<sup>+24</sup><sub>-47</sub></td><td>N</td><td>-0.72 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>167</td><td>15.6<sup>+0.7</sup><sub>-0.7</sub></td><td>468<sup>+31</sup><sub>-32</sub></td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.36 ± 0.10</td><td>Y?</td></tr><tr><td>2009 Dec 26</td><td>133</td><td>14.4<sup>+0.4</sup><sub>-0.2</sub></td><td>406<sup>+14</sup><sub>-13</sub></td><td>N</td><td>...</td><td>-0.35 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.48 ± 0.05</td><td>Y?</td></tr><tr><td colspan="2">Weighted average</td><td>14.0 ± 1.3</td><td>365 ± 67</td><td>...</td><td>...</td><td>...</td><td>-2.39 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.47 ± 0.02</td><td>Y</td></tr><tr><td rowspan="10">MHO 5</td><td>2009 Oct 27</td><td>58</td><td>43.3<sup>+0.3</sup><sub>-1.4</sub></td><td>125 ± 28</td><td>N</td><td>...</td><td>-2.51 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.31 ± 0.05</td><td>Y?</td></tr><tr><td>2009 Oct 30</td><td>78</td><td>43.1<sup>+0.3</sup><sub>-0.7</sub></td><td>&lt;125</td><td>N</td><td>-1.51 ± 0.05</td><td>-2.62 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.31 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>85</td><td>38.7<sup>+0.2</sup><sub>-0.9</sub></td><td>&lt;125</td><td>N</td><td>-0.85 ± 0.05</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>0.35 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>53</td><td>65.3<sup>+0.4</sup><sub>-0.3</sub></td><td>...</td><td>Y</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>≥ -0.90</td><td>0.35 ± 0.10</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>87</td><td>40.2<sup>+0.4</sup><sub>-0.3</sub></td><td>&lt;200</td><td>N</td><td>-1.28 ± 0.10</td><td>-3.01 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.30 ± 0.10</td><td>Y?</td></tr><tr><td>2009 Dec 10</td><td>113</td><td>38.7 ± 0.4</td><td>&lt;200</td><td>N</td><td>...</td><td>-2.43 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.41 ± 0.05</td><td>Y?</td></tr><tr><td>2009 Dec 26</td><td>78</td><td>38.9<sup>+0.3</sup><sub>-0.8</sub></td><td>&lt;125</td><td>Y</td><td>...</td><td>-2.43 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.40 ± 0.10</td><td>Y</td></tr><tr><td>2010 Nov 12</td><td>97</td><td>42.9 ± 7.5</td><td>&lt;175</td><td>N</td><td>-1.50 ± 0.20</td><td>-2.15 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.40 ± 0.10</td><td>Y</td></tr><tr><td>2010 Nov 13</td><td>46</td><td>36.4 ± 8.0</td><td>&lt;175</td><td>N</td><td>-1.52 ± 0.20</td><td>-1.59 ± 0.15</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2010 Nov 14</td><td>57</td><td>42.2 ± 5.0</td><td>&lt;175</td><td>N</td><td>-1.48 ± 0.20</td><td>-3.02 ± 0.10</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.43 ± 0.10</td><td>Y</td></tr><tr><td colspan="2">Weighted average</td><td>43.0 ± 8.4</td><td>&lt;175</td><td>...</td><td>...</td><td>...</td><td>-0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.35 ± 0.02</td><td>Y</td></tr><tr><td rowspan="10">V807 Tau</td><td>2009 Oct 27</td><td>196</td><td>11.0 ± 0.4</td><td>509<sup>+14</sup><sub>-13</sub></td><td>Y</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.49 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>231</td><td>11.8<sup>+0.3</sup><sub>-0.5</sub></td><td>474<sup>+13</sup><sub>-14</sub></td><td>Y</td><td>-0.22 ± 0.05</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.44 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>295</td><td>15.6<sup>+0.3</sup><sub>-0.6</sub></td><td>552<sup>+13</sup><sub>-16</sub></td><td>Y</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.47 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>307</td><td>19.7<sup>+0.2</sup><sub>-0.5</sub></td><td>...</td><td>Y</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>Y?</td></tr><tr><td>2009 Nov 23</td><td>150</td><td>8.9<sup>+0.1</sup><sub>-0.3</sub></td><td>530<sup>+19</sup><sub>-20</sub></td><td>Y</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.50 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 02</td><td>154</td><td>6.3<sup>+0.1</sup><sub>-0.4</sub></td><td>409 ± 19</td><td>Y</td><td>-0.71 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>190</td><td>11.7<sup>+0.2</sup><sub>-0.3</sub></td><td>591<sup>+25</sup><sub>-25</sub></td><td>Y</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.34 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>106</td><td>5.6 ± 0.1</td><td>387<sup>+13</sup><sub>-16</sub></td><td>Y</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.52 ± 0.05</td><td>Y</td></tr><tr><td colspan="2">Weighted average</td><td>11.3 ± 5.7</td><td>487 ± 75</td><td>...</td><td>...</td><td>...</td><td>-0.16 ± 0.05</td><td>-0.43 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.38 ± 0.05</td><td>Y</td></tr><tr><td rowspan="10">BP Tau</td><td>2009 Oct 27</td><td>164</td><td>58.5<sup>+1.0</sup><sub>-1.3</sub></td><td>374<sup>+12</sup><sub>-13</sub></td><td>N</td><td>...</td><td>-0.20 ± 0.05</td><td>-0.46 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.40 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>232</td><td>58.8<sup>+0.4</sup><sub>-1.0</sub></td><td>389 ± 12</td><td>N</td><td>-1.13 ± 0.05</td><td>-0.22 ± 0.05</td><td>-0.37 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.40 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>206</td><td>52.3<sup>+1.0</sup><sub>-1.3</sub></td><td>391 ± 12</td><td>N</td><td>-1.12 ± 0.05</td><td>-0.22 ± 0.05</td><td>-0.37 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.40 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>317</td><td>54.4<sup>+0.2</sup><sub>-0.8</sub></td><td>...</td><td>Y</td><td>-0.70 ± 0.20</td><td>≥ -0.60</td><td>≥ -0.60</td><td>-0.63 ± 0.20</td><td>-0.60</td><td>-0.60</td><td>-0.60</td><td>≤ 0.60</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>235</td><td>65.4<sup>+0.3</sup><sub>-0.5</sub></td><td>420<sup>+20</sup><sub>-20</sub></td><td>N</td><td>-2.74 ± 0.10</td><td>≥ -0.30</td><td>-0.73 ± 0.10</td><td>-0.80 ± 0.10</td><td>-0.88 ± 0.10</td><td>-0.58 ± 0.10</td><td>0.30 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>134</td><td>44.0<sup>+0.4</sup><sub>-1.4</sub></td><td>440<sup>+20</sup><sub>-20</sub></td><td>N</td><td>-2.46 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>172</td><td>141<sup>+2</sup><sub>-4</sub></td><td>504<sup>+19</sup><sub>-20</sub></td><td>N</td><td>...</td><td>-0.41 ± 0.10</td><td>-0.56 ± 0.10</td><td>-0.90 ± 0.10</td><td>-1.40 ± 0.10</td><td>-0.82 ± 0.10</td><td>≤ 0.30</td><td>Y</td></tr></tbody></table>
<table><caption>Table 3 – continued</caption><thead><tr><th>Target</th><th>Date</th><th>SNR</th><th>EW(Hα) [Å]</th><th>W<sub>10</sub> [km s<sup>-1</sup>]</th><th>Asym. Profile</th><th>He I 5876</th><th>[OⅠ] 6300</th><th>Other emission lines EW [Å]<br>He I 6678<br>Ca 8498</th><th>Ca 8542</th><th>Ca 8662</th><th>Li 6707 EW [Å]</th><th>Accretor</th></tr></thead><tbody><tr><td rowspan="10">CY Tau</td><td>2009 Dec 26</td><td>130</td><td>49.3<sup>+0.2</sup><sub>-0.5</sub><br>65.5 ± 33.1</td><td>388<sup>+12</sup><sub>-13</sub><br>401 ± 48</td><td>N</td><td>...</td><td>-0.43 ± 0.05</td><td>-0.44 ± 0.05</td><td>...</td><td>...</td><td>0.47 ± 0.05</td><td>Y</td></tr><tr><td>Weighted average</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.41 ± 0.02</td><td>Y</td></tr><tr><td>2009 Oct 27</td><td>94</td><td>41.6 ± 0.5</td><td>376 ± 14</td><td>N</td><td>...</td><td>-0.24 ± 0.05</td><td>-0.25 ± 0.05</td><td>...</td><td>...</td><td>0.53 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>190</td><td>33.3<sup>+0.2</sup><sub>-0.4</sub></td><td>319 ± 14</td><td>N</td><td>-0.40 ± 0.05</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>0.34 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>142</td><td>48.2<sup>+0.5</sup><sub>-1.4</sub></td><td>448<sup>+14</sup><sub>-15</sub></td><td>Y</td><td>-0.65 ± 0.05</td><td>-0.21 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>0.36 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>159</td><td>44.2<sup>+0.3</sup><sub>-1.0</sub></td><td>...</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>Y?</td></tr><tr><td>2009 Nov 23</td><td>157</td><td>29.7<sup>+0.5</sup><sub>-1.6</sub></td><td>301<sup>+24</sup><sub>-30</sub></td><td>N</td><td>-0.41 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.40 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>78</td><td>40.0<sup>+0.4</sup><sub>-0.7</sub></td><td>295<sup>+21</sup><sub>-22</sub></td><td>N</td><td>≥ -0.45</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y?</td></tr><tr><td>2009 Dec 10</td><td>147</td><td>31.1<sup>+0.2</sup><sub>-0.7</sub></td><td>321 ± 23</td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.42 ± 0.10</td><td>Y?</td></tr><tr><td>2009 Dec 26</td><td>173</td><td>37.1<sup>+0.5</sup><sub>-0.4</sub></td><td>407 ± 14</td><td>Y</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>0.46 ± 0.05</td><td>Y</td></tr><tr><td>Weighted average</td><td></td><td>38.2 ± 6.9</td><td>370 ± 62</td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.42 ± 0.02</td><td>Y</td></tr><tr><td rowspan="10">DE Tau</td><td>2009 Oct 27</td><td>122</td><td>48.5<sup>+0.3</sup><sub>-0.4</sub></td><td>430 ± 14</td><td>Y</td><td>...</td><td>-0.23 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>0.48 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>211</td><td>44.5<sup>+0.3</sup><sub>-0.4</sub></td><td>443 ± 14</td><td>Y</td><td>-0.76 ± 0.05</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>0.40 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>183</td><td>48.8<sup>+0.9</sup><sub>-0.6</sub></td><td>429 ± 14</td><td>Y</td><td>-0.75 ± 0.05</td><td>-0.17 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>0.42 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>141</td><td>55.4<sup>+1.0</sup><sub>-0.6</sub></td><td>...</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>-6.60 ± 0.20</td><td>-7.47 ± 0.20</td><td>-5.99 ± 0.20</td><td>≤ 0.60</td></tr><tr><td>2009 Nov 23</td><td>158</td><td>50.0<sup>+0.3</sup><sub>-1.6</sub></td><td>452<sup>+22</sup><sub>-23</sub></td><td>N</td><td>-0.73 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>-5.55 ± 0.15</td><td>-5.73 ± 0.15</td><td>-4.51 ± 0.15</td><td>0.32 ± 0.10</td></tr><tr><td>2009 Dec 03</td><td>86</td><td>55.6<sup>+0.5</sup><sub>-0.7</sub></td><td>472<sup>+21</sup><sub>-22</sub></td><td>N</td><td>-1.88 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>251</td><td>56.3<sup>+0.4</sup><sub>-0.7</sub></td><td>475<sup>+21</sup><sub>-22</sub></td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>-8.78 ± 0.20</td><td>-9.05 ± 0.20</td><td>-7.19 ± 0.20</td><td>0.33 ± 0.10</td></tr><tr><td>2009 Dec 26</td><td>153</td><td>44.9<sup>+0.4</sup><sub>-0.6</sub></td><td>419 ± 14</td><td>Y</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>0.50 ± 0.05</td><td>Y</td></tr><tr><td>Weighted average</td><td></td><td>50.5 ± 4.8</td><td>439 ± 23</td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.44 ± 0.02</td><td>Y</td></tr><tr><td rowspan="10">DH Tau</td><td>2009 Oct 31</td><td>153</td><td>23.7<sup>+0.3</sup><sub>-0.4</sub></td><td>227<sup>+14</sup><sub>-16</sub></td><td>N</td><td>-1.45 ± 0.05</td><td>-0.52 ± 0.05</td><td>-0.30 ± 0.05</td><td>...</td><td>...</td><td>0.50 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>214</td><td>24.8 ± 0.8</td><td>...</td><td>...</td><td>-0.70 ± 0.20</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>-0.67 ± 0.20</td><td>≥ -0.60</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>129</td><td>40.5<sup>+0.6</sup><sub>-0.7</sub></td><td>327<sup>+22</sup><sub>-24</sub></td><td>N</td><td>-3.47 ± 0.15</td><td>-0.86 ± 0.15</td><td>≥ -0.45</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>159</td><td>31.0<sup>+0.2</sup><sub>-0.7</sub></td><td>293 ± 14</td><td>N</td><td>...</td><td>-0.75 ± 0.05</td><td>-0.60 ± 0.05</td><td>...</td><td>...</td><td>0.44 ± 0.05</td><td>Y</td></tr><tr><td>2010 Nov 12</td><td>169</td><td>32.9<sup>+0.2</sup><sub>-0.7</sub></td><td>206 ± 21</td><td>N</td><td>-2.11 ± 0.10</td><td>-0.70 ± 0.10</td><td>-0.95 ± 0.10</td><td>...</td><td>...</td><td>0.33 ± 0.10</td><td>Y</td></tr><tr><td>2010 Nov 13</td><td>179</td><td>29.1<sup>+0.3</sup><sub>-0.4</sub></td><td>176<sup>+22</sup><sub>-23</sub></td><td>N</td><td>-2.22 ± 0.10</td><td>-0.77 ± 0.10</td><td>-0.64 ± 0.10</td><td>...</td><td>...</td><td>0.34 ± 0.10</td><td>Y</td></tr><tr><td>2010 Nov 14</td><td>167</td><td>40.7 ± 0.4</td><td>236 ± 20</td><td>N</td><td>-1.95 ± 0.10</td><td>-0.80 ± 0.10</td><td>-0.60 ± 0.10</td><td>...</td><td>...</td><td>0.36 ± 0.10</td><td>Y</td></tr><tr><td>Weighted average</td><td></td><td>31.8 ± 7.3</td><td>249 ± 57</td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.44 ± 0.03</td><td>Y</td></tr><tr><td rowspan="10">DS Tau</td><td>2009 Oct 27</td><td>128</td><td>60.6<sup>+0.9</sup><sub>-1.3</sub></td><td>520<sup>+12</sup><sub>-13</sub></td><td>Y</td><td>...</td><td>≥ -0.15</td><td>-0.21 ± 0.05</td><td>...</td><td>...</td><td>0.40 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>250</td><td>31.0<sup>+0.4</sup><sub>-0.6</sub></td><td>506<sup>+12</sup><sub>-13</sub></td><td>Y</td><td>-1.22 ± 0.05</td><td>≥ -0.15</td><td>-0.48 ± 0.05</td><td>...</td><td>...</td><td>0.25 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>230</td><td>38.8<sup>+0.5</sup><sub>-1.4</sub></td><td>436<sup>+12</sup><sub>-14</sub></td><td>Y</td><td>-1.57 ± 0.05</td><td>≥ -0.15</td><td>-0.64 ± 0.05</td><td>...</td><td>...</td><td>0.29 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>390</td><td>24.2<sup>+0.2</sup><sub>-0.4</sub></td><td>...</td><td>...</td><td>-1.11 ± 0.20</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>158</td><td>27.0<sup>+0.4</sup><sub>-0.7</sub></td><td>531<sup>+19</sup><sub>-20</sub></td><td>N</td><td>-1.55 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≤ 0.30</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>123</td><td>31.2<sup>+0.4</sup><sub>-0.8</sub></td><td>479<sup>+19</sup><sub>-20</sub></td><td>N</td><td>-1.90 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>188</td><td>58.7<sup>+0.3</sup><sub>-1.5</sub></td><td>485<sup>+19</sup><sub>-20</sub></td><td>N</td><td>...</td><td>≥ -0.30</td><td>-0.57 ± 0.10</td><td>-0.33 ± 0.10</td><td>-0.56 ± 0.10</td><td>-0.34 ± 0.10</td><td>≤ 0.30</td></tr><tr><td>2009 Dec 26</td><td>170</td><td>35.8<sup>+0.5</sup><sub>-0.2</sub></td><td>468<sup>+12</sup><sub>-20</sub></td><td>Y</td><td>...</td><td>-0.23 ± 0.05</td><td>-0.39 ± 0.05</td><td>...</td><td>...</td><td>0.33 ± 0.05</td><td>Y</td></tr><tr><td>Weighted average</td><td></td><td>38.4 ± 15.4</td><td>488 ± 33</td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.32 ± 0.02</td><td>Y</td></tr></tbody></table>
<table><caption>Table 3 – continued</caption><thead><tr><th>Target</th><th>Date</th><th>SNR</th><th>EW(H[α]) [Å]</th><th>W<sub>10</sub> [km s<sup>-1</sup>]</th><th>Asym. Profile</th><th>He<sub>1</sub> 5876</th><th>[OⅠ] 6300</th><th>Other emission lines EW [Å]</th><th>He<sub>1</sub> 6678</th><th>Ca 8498</th><th>Ca 8542</th><th>Ca 8662</th><th>Li 6707 EW [Å]</th><th>Accretor</th></tr></thead><tbody><tr><td rowspan="10">FM Tau</td><td>2009 Oct 27</td><td>169</td><td>58.3<sup>+0.3</sup><sub>-1.4</sub></td><td>343 ± 20</td><td>N</td><td>...</td><td>...</td><td>-0.35 ± 0.05</td><td>-0.96 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>≤ 0.15</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>132</td><td>60.1<sup>+0.4</sup><sub>-1.3</sub></td><td>325 ± 20</td><td>N</td><td>-2.00 ± 0.05</td><td>-0.40 ± 0.05</td><td>-1.08 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.16 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>155</td><td>55.9<sup>+0.2</sup><sub>-1.6</sub></td><td>309<sup>+20</sup><sub>-21</sub></td><td>N</td><td>-2.31 ± 0.05</td><td>-0.54 ± 0.05</td><td>-1.03 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.23 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>246</td><td>59.7<sup>+0.1</sup><sub>-1.1</sub></td><td>...</td><td>...</td><td>-3.64 ± 0.20</td><td>≥ -0.60</td><td>-1.22 ± 0.20</td><td>-1.07 ± 0.20</td><td>-1.34 ± 0.20</td><td>-1.04 ± 0.20</td><td>...</td><td>≤ 0.60</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>193</td><td>65.0<sup>+0.4</sup><sub>-1.0</sub></td><td>366 ± 31</td><td>N</td><td>-4.20 ± 0.10</td><td>-0.61 ± 0.10</td><td>-1.45 ± 0.10</td><td>-1.57 ± 0.10</td><td>-2.25 ± 0.10</td><td>-1.59 ± 0.10</td><td>...</td><td>≤ 0.30</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>152</td><td>54.9<sup>+0.6</sup><sub>-2.4</sub></td><td>376<sup>+30</sup><sub>-31</sub></td><td>N</td><td>-4.12 ± 0.15</td><td>≥ -0.45</td><td>-1.51 ± 0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>244</td><td>59.5<sup>+0.3</sup><sub>-1.5</sub></td><td>387<sup>+30</sup><sub>-31</sub></td><td>N</td><td>...</td><td>...</td><td>-0.48 ± 0.10</td><td>-1.17 ± 0.10</td><td>-0.77 ± 0.10</td><td>-1.33 ± 0.10</td><td>-0.93 ± 0.10</td><td>...</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>164</td><td>63.6<sup>+0.4</sup><sub>-1.9</sub></td><td>387 ± 20</td><td>N</td><td>...</td><td>...</td><td>-0.74 ± 0.05</td><td>-1.18 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.17 ± 0.05</td><td>Y</td></tr><tr><td>2010 Nov 11</td><td>134</td><td>51.7<sup>+0.4</sup><sub>-1.2</sub></td><td>304 ± 26</td><td>N</td><td>-2.65 ± 0.10</td><td>-0.49 ± 0.10</td><td>-0.84 ± 0.10</td><td>...</td><td>...</td><td>...</td><td>...</td><td>≤ 0.30</td><td>Y</td></tr><tr><td colspan="2">Weighted average</td><td>58.8 ± 4.2</td><td>345 ± 34</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.19 ± 0.03</td><td>Y</td></tr><tr><td rowspan="10">FP Tau</td><td>2009 Oct 27</td><td>134</td><td>15.6<sup>+0.6</sup><sub>-0.2</sub></td><td>385<sup>+15</sup><sub>-14</sub></td><td>Y</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.50 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>164</td><td>20.0<sup>+0.5</sup><sub>-0.4</sub></td><td>420 ± 14</td><td>Y</td><td>-0.32 ± 0.05</td><td>-0.22 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.45 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>130</td><td>25.4<sup>+0.2</sup><sub>-0.1</sub></td><td>445 ± 14</td><td>Y</td><td>-0.44 ± 0.05</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.48 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>130</td><td>14.6<sup>+0.4</sup><sub>-0.1</sub></td><td>...</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>...</td><td>?</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>111</td><td>18.3<sup>+0.3</sup><sub>-0.7</sub></td><td>474<sup>+22</sup><sub>-27</sub></td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.42 ± 0.10</td><td>Y?</td><td>Y?</td></tr><tr><td>2009 Dec 03</td><td>67</td><td>13.1<sup>+0.2</sup><sub>-0.3</sub></td><td>455<sup>+21</sup><sub>-22</sub></td><td>N</td><td>≥ -0.45</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>0.40 ± 0.10</td><td>Y?</td><td>Y?</td></tr><tr><td>2009 Dec 10</td><td>140</td><td>13.0<sup>+0.1</sup><sub>-0.3</sub></td><td>474 ± 22</td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.40 ± 0.10</td><td>Y?</td><td>Y?</td></tr><tr><td>2009 Dec 26</td><td>96</td><td>20.9<sup>+0.4</sup><sub>-0.6</sub></td><td>464<sup>+14</sup><sub>-15</sub></td><td>Y</td><td>...</td><td>-0.22 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.66 ± 0.05</td><td>Y</td></tr><tr><td colspan="2">Weighted average</td><td>17.6 ± 4.7</td><td>438 ± 33</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.49 ± 0.04</td><td>Y</td></tr><tr><td rowspan="10">FQ Tau</td><td>2009 Oct 30</td><td>104</td><td>68.4<sup>+0.7</sup><sub>-2.7</sub></td><td>503<sup>+20</sup><sub>-21</sub></td><td>Y</td><td>-1.72 ± 0.05</td><td>-0.18 ± 0.05</td><td>-0.51 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.38 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>139</td><td>55.6<sup>+0.7</sup><sub>-0.7</sub></td><td>539 ± 20</td><td>Y</td><td>-2.87 ± 0.05</td><td>-0.20 ± 0.05</td><td>-1.20 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.32 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>90</td><td>43.8<sup>+0.1</sup><sub>-0.3</sub></td><td>...</td><td>...</td><td>-4.84 ± 0.20</td><td>≥ -0.60</td><td>-0.80 ± 0.20</td><td>-3.44 ± 0.20</td><td>-3.29 ± 0.20</td><td>-2.49 ± 0.20</td><td>...</td><td>0.85 ± 0.20</td><td>Y</td></tr><tr><td>2009 Dec 02</td><td>40</td><td>59.7<sup>+0.8</sup><sub>-0.6</sub></td><td>502 ± 30</td><td>Y</td><td>-3.21 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.38 ± 0.05</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>114</td><td>32.9<sup>+0.1</sup><sub>-0.6</sub></td><td>469 ± 20</td><td>Y</td><td>...</td><td>-0.29 ± 0.05</td><td>-0.47 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.38 ± 0.03</td><td>Y</td></tr><tr><td colspan="2">Weighted average</td><td>52.1 ± 15.8</td><td>504 ± 29</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.49 ± 0.05</td><td>Y</td></tr><tr><td rowspan="10">FY Tau</td><td>2009 Oct 27</td><td>110</td><td>60.2<sup>+0.4</sup><sub>-0.9</sub></td><td>475 ± 12</td><td>N</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.49 ± 0.05</td><td>Y?</td></tr><tr><td>2009 Oct 30</td><td>174</td><td>33.1<sup>+0.4</sup><sub>-0.9</sub></td><td>461<sup>+12</sup><sub>-14</sub></td><td>Y</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.47 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>162</td><td>43.8<sup>+0.4</sup><sub>-0.8</sub></td><td>465 ± 12</td><td>N</td><td>-0.26 ± 0.05</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.45 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>308</td><td>50.1<sup>+0.5</sup><sub>-0.4</sub></td><td>...</td><td>...</td><td>-0.84 ± 0.20</td><td>≥ -0.60</td><td>≥ -0.60</td><td>-2.02 ± 0.20</td><td>-2.30 ± 0.20</td><td>-1.98 ± 0.20</td><td>...</td><td>0.36 ± 0.10</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>176</td><td>52.6<sup>+0.4</sup><sub>-0.8</sub></td><td>471<sup>+19</sup><sub>-20</sub></td><td>N</td><td>-0.53 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>-1.55 ± 0.10</td><td>-2.11 ± 0.10</td><td>-1.67 ± 0.10</td><td>...</td><td>0.45 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>105</td><td>36.1<sup>+0.3</sup><sub>-1.2</sub></td><td>491<sup>+19</sup><sub>-21</sub></td><td>N</td><td>-0.78 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.31 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>208</td><td>26.6<sup>+0.3</sup><sub>-0.7</sub></td><td>526<sup>+19</sup><sub>-21</sub></td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>-0.47 ± 0.10</td><td>-0.66 ± 0.10</td><td>-0.36 ± 0.10</td><td>...</td><td>0.48 ± 0.05</td><td>Y?</td></tr><tr><td>2009 Dec 26</td><td>130</td><td>39.9<sup>+0.3</sup><sub>-1.6</sub></td><td>440<sup>+12</sup><sub>-14</sub></td><td>N</td><td>...</td><td>-0.21 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.46 ± 0.02</td><td>Y</td></tr><tr><td colspan="2">Weighted average</td><td>44.0 ± 10.0</td><td>469 ± 28</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.46 ± 0.02</td><td>Y</td></tr></tbody></table>
<table><caption>Table 3 – continued</caption><thead><tr><th>Target</th><th>Date</th><th>SNR</th><th>EW(Hα) [Å]</th><th>W<sub>10</sub> [km s<sup>-1</sup>]</th><th>Asym. Profile</th><th>He<sub>1</sub> 5876</th><th>[OⅠ] 6300</th><th>Other emission lines EW [Å]</th><th>Ca 8498</th><th>Ca 8542</th><th>Ca 8662</th><th>Li 6707 EW [Å]</th><th>Accretor</th></tr></thead><tbody><tr><td rowspan="5">FZ Tau</td><td>2009 Oct 30</td><td>144</td><td>119<sup>+3</sup><sub>-5</sub></td><td>497<sup>+12</sup><sub>-12</sub></td><td>Y</td><td>-6.13 ± 0.10</td><td>-0.51 ± 0.05</td><td>-1.69 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.18 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>153</td><td>136<sup>+3</sup><sub>-6</sub></td><td>494<sup>+12</sup><sub>-13</sub></td><td>Y</td><td>-4.90 ± 0.10</td><td>-0.37 ± 0.05</td><td>-2.09 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>≤ 0.15</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>98</td><td>154<sup>+1</sup><sub>-3</sub></td><td>...</td><td>...</td><td>-2.73 ± 0.20</td><td>≥ -0.60</td><td>-2.06 ± 0.20</td><td>-42.9 ± 0.8</td><td>-51.5 ± 1.0</td><td>-42.9 ± 0.8</td><td>≤ 0.60</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>154</td><td>109<sup>+1</sup><sub>-3</sub></td><td>511 ± 12</td><td>Y</td><td>...</td><td>-0.41 ± 0.05</td><td>-1.90 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.19 ± 0.05</td><td>Y</td></tr><tr><td>Weighted average</td><td></td><td>1.0 ± 0.2</td><td>&lt;175</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.19 ± 0.04</td><td>Y</td></tr><tr><td rowspan="10">GI Tau</td><td>2009 Oct 27</td><td>106</td><td>30.3<sup>+0.4</sup><sub>-0.6</sub></td><td>302<sup>+12</sup><sub>-13</sub></td><td>N</td><td>...</td><td>-0.34 ± 0.05</td><td>-0.85 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.32 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>208</td><td>32.5<sup>+0.3</sup><sub>-0.4</sub></td><td>246 ± 12</td><td>N</td><td>-1.24 ± 0.05</td><td>-0.98 ± 0.05</td><td>-0.65 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.38 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>151</td><td>28.5<sup>+0.3</sup><sub>-0.7</sub></td><td>311<sup>+12</sup><sub>-13</sub></td><td>N</td><td>-2.40 ± 0.05</td><td>-0.51 ± 0.05</td><td>-1.02 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.35 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>283</td><td>34.6<sup>+0.8</sup><sub>-0.8</sub></td><td>...</td><td>...</td><td>-2.22 ± 0.20</td><td>≥ -0.60</td><td>-0.61 ± 0.20</td><td>-0.87 ± 0.20</td><td>-1.03 ± 0.20</td><td>-0.93 ± 0.20</td><td>≤ 0.60</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>190</td><td>8.6<sup>+0.1</sup><sub>-0.2</sub></td><td>357<sup>+20</sup><sub>-22</sub></td><td>N</td><td>-1.83 ± 0.10</td><td>≥ -0.30</td><td>-0.54 ± 0.10</td><td>-0.51 ± 0.10</td><td>-0.48 ± 0.10</td><td>≥ -0.30</td><td>0.37 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>69</td><td>11.9<sup>+0.2</sup><sub>-0.3</sub></td><td>206<sup>+22</sup><sub>-26</sub></td><td>N</td><td>-1.36 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>0.57 ± 0.15</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>142</td><td>7.1<sup>+0.1</sup><sub>-0.2</sub></td><td>344<sup>+21</sup><sub>-24</sub></td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.39 ± 0.10</td><td>Y?</td></tr><tr><td>2009 Dec 26</td><td>127</td><td>13.8<sup>+0.2</sup><sub>-0.4</sub></td><td>320<sup>+12</sup><sub>-13</sub></td><td>Y</td><td>...</td><td>-0.38 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.50 ± 0.05</td><td>Y</td></tr><tr><td>Weighted average</td><td></td><td>20.9 ± 15.8</td><td>297 ± 54</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.39 ± 0.02</td><td>Y</td></tr><tr><td rowspan="10">GK Tau</td><td>2009 Oct 27</td><td>134</td><td>27.9<sup>+0.7</sup><sub>-0.8</sub></td><td>524<sup>+13</sup><sub>-14</sub></td><td>Y</td><td>...</td><td>≥ -0.15</td><td>-0.16 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.32 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>340</td><td>32.3<sup>+0.6</sup><sub>-0.4</sub></td><td>504<sup>+12</sup><sub>-14</sub></td><td>Y</td><td>-0.82 ± 0.05</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.41 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>294</td><td>24.6 ± 0.3</td><td>511 ± 12</td><td>Y</td><td>-0.81 ± 0.05</td><td>-0.21 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.36 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>297</td><td>43.6<sup>+0.2</sup><sub>-0.8</sub></td><td>...</td><td>...</td><td>-1.85 ± 0.20</td><td>≥ -0.60</td><td>≥ -0.60</td><td>-9.78 ± 0.25</td><td>-11.5 ± 0.3</td><td>-9.37 ± 0.25</td><td>≤ 0.60</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>231</td><td>5.4 ± 0.1</td><td>492<sup>+19</sup><sub>-21</sub></td><td>N</td><td>-0.40 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.33 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>110</td><td>18.5<sup>+0.1</sup><sub>-0.4</sub></td><td>474<sup>+19</sup><sub>-21</sub></td><td>N</td><td>-1.46 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>168</td><td>30.5<sup>+0.4</sup><sub>-0.9</sub></td><td>533<sup>+19</sup><sub>-21</sub></td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>-1.20 ± 0.10</td><td>-2.19 ± 0.10</td><td>-1.42 ± 0.10</td><td>0.33 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>267</td><td>30.8<sup>+0.4</sup><sub>-0.1</sub></td><td>517<sup>+12</sup><sub>-13</sub></td><td>Y</td><td>...</td><td>-0.26 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.46 ± 0.05</td><td>Y</td></tr><tr><td>Weighted average</td><td></td><td>26.7 ± 21.1</td><td>510 ± 20</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.38 ± 0.02</td><td>Y</td></tr><tr><td rowspan="10">LkCa 15</td><td>2009 Oct 27</td><td>133</td><td>10.0<sup>+0.4</sup><sub>-0.3</sub></td><td>431<sup>+13</sup><sub>-13</sub></td><td>Y</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.43 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>325</td><td>18.1<sup>+0.4</sup><sub>-0.6</sub></td><td>620<sup>+20</sup><sub>-20</sub></td><td>Y</td><td>-0.39 ± 0.05</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.38 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>188</td><td>16.9<sup>+0.2</sup><sub>-0.5</sub></td><td>617<sup>+13</sup><sub>-16</sub></td><td>Y</td><td>-0.36 ± 0.05</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.35 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>333</td><td>31.3<sup>+0.2</sup><sub>-0.6</sub></td><td>...</td><td>...</td><td>-1.01 ± 0.20</td><td>≥ -0.60</td><td>≥ -0.60</td><td>-1.43 ± 0.20</td><td>-1.73 ± 0.20</td><td>-1.61 ± 0.20</td><td>≤ 0.60</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>163</td><td>15.5<sup>+0.3</sup><sub>-1.0</sub></td><td>596<sup>+20</sup><sub>-44</sub></td><td>Y</td><td>-1.19 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.36 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>108</td><td>23.5<sup>+0.1</sup><sub>-0.4</sub></td><td>639<sup>+18</sup><sub>-19</sub></td><td>Y</td><td>-1.03 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>177</td><td>28.6<sup>+0.3</sup><sub>-0.5</sub></td><td>599<sup>+19</sup><sub>-19</sub></td><td>Y</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≤ 0.30</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>178</td><td>32.0<sup>+0.3</sup><sub>-0.7</sub></td><td>597<sup>+12</sup><sub>-13</sub></td><td>Y</td><td>...</td><td>≥ -0.15</td><td>-0.19 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.38 ± 0.05</td><td>Y</td></tr><tr><td>Weighted average</td><td></td><td>22.0 ± 8.1</td><td>574 ± 71</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.38 ± 0.02</td><td>Y</td></tr><tr><td rowspan="3">UX Tau A</td><td>2009 Oct 27</td><td>242</td><td>8.7 ± 0.1</td><td>493<sup>+21</sup><sub>-22</sub></td><td>Y</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.34 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>227</td><td>6.4 ± 0.1</td><td>539 ± 22</td><td>Y</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.33 ± 0.05</td><td>Y</td></tr></tbody></table>
<table><caption>Table 3 – continued</caption><thead><tr><th>Target</th><th>Date</th><th>SNR</th><th>EW(Hα) [Å]</th><th>W<sub>10</sub> [km s<sup>-1</sup>]</th><th>Asym. Profile</th><th>He I 15876</th><th>Other emission lines EW [Å]</th><th>He I 6678</th><th>Ca 8498</th><th>Ca 8542</th><th>Ca 8662</th><th>Li 6707 EW [Å]</th><th>Accretor</th></tr></thead><tbody><tr><td rowspan="10">V710 Tau</td><td>2009 Oct 31</td><td>225</td><td>4.6 ± 0.1</td><td>503 ± 22</td><td>Y</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.36 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>407</td><td>13.6<sup>+0.1</sup><sub>-0.3</sub></td><td>...</td><td>...</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≥ -0.60</td><td>≤ 0.60</td><td>Y?</td></tr><tr><td>2009 Nov 23</td><td>133</td><td>10.7 ± 0.1</td><td>539<sup>+33</sup><sub>-35</sub></td><td>Y</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≤ 0.30</td><td>Y</td></tr><tr><td>2009 Dec 02</td><td>104</td><td>3.7 ± 0.1</td><td>592<sup>+33</sup><sub>-36</sub></td><td>Y</td><td>-0.84 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>115</td><td>8.9 ± 0.1</td><td>506 ± 33</td><td>Y</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≤ 0.30</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>177</td><td>5.5 ± 0.1</td><td>460 ± 22</td><td>Y</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.29 ± 0.05</td><td>Y</td></tr><tr><td>2010 Nov 12</td><td>167</td><td>2.4 ± 0.1</td><td>379 ± 29</td><td>Y</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>≤ 0.30</td><td>Y</td></tr><tr><td>Weighted average</td><td></td><td>7.2 ± 3.6</td><td>497 ± 63</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.33 ± 0.03</td><td>Y</td></tr><tr><td>2009 Oct 27</td><td>110</td><td>32.9<sup>+0.1</sup><sub>-0.6</sub></td><td>316 ± 17</td><td>Y</td><td>...</td><td>-0.21 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.51 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>193</td><td>25.7<sup>+0.1</sup><sub>-0.4</sub></td><td>307 ± 17</td><td>Y</td><td>-1.15 ± 0.05</td><td>-0.17 ± 0.05</td><td>-0.21 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.46 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>177</td><td>28.5<sup>+0.1</sup><sub>-0.3</sub></td><td>297 ± 17</td><td>N</td><td>-0.70 ± 0.05</td><td>-0.18 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.54 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 23</td><td>149</td><td>22.2 ± 0.2</td><td>291 ± 27</td><td>N</td><td>-0.72 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.41 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>114</td><td>29.1<sup>+0.3</sup><sub>-0.5</sub></td><td>357<sup>+25</sup><sub>-26</sub></td><td>N</td><td>-1.21 ± 0.15</td><td>≥ -0.45</td><td>≥ -0.45</td><td>...</td><td>...</td><td>...</td><td>...</td><td>≤ 0.45</td><td>Y</td></tr><tr><td>2009 Dec 10</td><td>155</td><td>26.5<sup>+0.1</sup><sub>-0.3</sub></td><td>350<sup>+26</sup><sub>-27</sub></td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.33 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>147</td><td>15.2 ± 0.1</td><td>259 ± 17</td><td>N</td><td>...</td><td>-0.28 ± 0.05</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.55 ± 0.05</td><td>Y</td></tr><tr><td>2010 Nov 11</td><td>178</td><td>26.3<sup>+0.1</sup><sub>-0.3</sub></td><td>295 ± 22</td><td>N</td><td>-0.39 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.39 ± 0.10</td><td>Y</td></tr><tr><td>Weighted average</td><td></td><td>25.8 ± 5.3</td><td>303 ± 33</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.49 ± 0.02</td><td>Y</td></tr><tr><td rowspan="10">MHO 4</td><td>2009 Oct 27</td><td>35</td><td>30.2<sup>+0.3</sup><sub>-1.3</sub></td><td>&lt;125</td><td>N</td><td>...</td><td>≥ -0.15</td><td>-0.26 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.49 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 30</td><td>45</td><td>28.0<sup>+0.4</sup><sub>-0.4</sub></td><td>&lt;125</td><td>N</td><td>...</td><td>≥ -0.15</td><td>-0.34 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.38 ± 0.05</td><td>Y</td></tr><tr><td>2009 Oct 31</td><td>44</td><td>36.5<sup>+1.7</sup><sub>-1.7</sub></td><td>&lt;125</td><td>N</td><td>...</td><td>≥ -0.15</td><td>-0.58 ± 0.05</td><td>...</td><td>...</td><td>...</td><td>0.46 ± 0.05</td><td>Y</td></tr><tr><td>2009 Nov 07</td><td>41</td><td>38.9 ± 0.4</td><td>...</td><td>...</td><td>≥ -4.0</td><td>≥ -1.20</td><td>≥ -1.20</td><td>≥ -1.20</td><td>≥ -1.20</td><td>≥ -1.20</td><td>≤ 1.20</td><td>Y?</td></tr><tr><td>2009 Nov 23</td><td>141</td><td>42.5<sup>+0.4</sup><sub>-0.7</sub></td><td>&lt;200</td><td>N</td><td>-1.67 ± 0.20</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.39 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 03</td><td>15</td><td>39.6 ± 0.3</td><td>&lt;200</td><td>N</td><td>≥ -1.2</td><td>≥ -0.75</td><td>≥ -0.75</td><td>≥ -0.75</td><td>...</td><td>...</td><td>...</td><td>Y?</td></tr><tr><td>2009 Dec 10</td><td>82</td><td>46.7<sup>+0.3</sup><sub>-0.5</sub></td><td>225<sup>+43</sup><sub>-45</sub></td><td>...</td><td>...</td><td>≥ -0.30</td><td>-0.45 ± 0.10</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.33 ± 0.10</td><td>Y</td></tr><tr><td>2009 Dec 26</td><td>12</td><td>35.3<sup>+0.7</sup><sub>-0.7</sub></td><td>&lt;125</td><td>N</td><td>...</td><td>≥ -0.35</td><td>≥ -0.35</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0.45 ± 0.10</td><td>Y?</td></tr><tr><td>2010 Nov 12</td><td>69</td><td>33.4<sup>+2.0</sup><sub>-4.0</sub></td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>0.50 ± 0.10</td><td>Y?</td></tr><tr><td>2010 Nov 13</td><td>32</td><td>37.7<sup>+1.7</sup><sub>-3.3</sub></td><td>&lt;175</td><td>N</td><td>≥ -0.60</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>≤ 0.60</td><td>Y?</td></tr><tr><td>2010 Nov 14</td><td>40</td><td>37.6<sup>+1.5</sup><sub>-0.6</sub></td><td>&lt;175</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>...</td><td>...</td><td>...</td><td>...</td><td>≤ 0.60</td><td>Y?</td></tr><tr><td>Weighted average</td><td></td><td>36.9 ± 5.3</td><td>&lt;175</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.44 ± 0.02</td><td>Y?</td></tr><tr><td rowspan="10">UX Tau C</td><td>2009 Oct 27</td><td>126</td><td>4.0<sup>+0.1</sup><sub>-0.2</sub></td><td>&lt;125</td><td>N</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.57 ± 0.05</td><td>N</td></tr><tr><td>2009 Oct 30</td><td>152</td><td>4.0<sup>+0.1</sup><sub>-0.2</sub></td><td>&lt;125</td><td>N</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.53 ± 0.05</td><td>N</td></tr><tr><td>2009 Oct 31</td><td>167</td><td>4.0 ± 0.1</td><td>&lt;125</td><td>N</td><td>≥ -0.15</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.57 ± 0.05</td><td>N</td></tr><tr><td>2009 Nov 23</td><td>131</td><td>4.0 ± 0.1</td><td>&lt;200</td><td>N</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.38 ± 0.10</td><td>N</td></tr><tr><td>2009 Dec 10</td><td>101</td><td>5.1<sup>+0.2</sup><sub>-0.3</sub></td><td>&lt;200</td><td>N</td><td>...</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>≥ -0.30</td><td>0.39 ± 0.10</td><td>N</td></tr><tr><td>2009 Dec 26</td><td>103</td><td>3.8<sup>+0.1</sup><sub>-0.3</sub></td><td>&lt;125</td><td>N</td><td>...</td><td>≥ -0.15</td><td>≥ -0.15</td><td>...</td><td>...</td><td>...</td><td>0.52 ± 0.05</td><td>N</td></tr><tr><td>Weighted average</td><td></td><td>4.2 ± 0.5</td><td>&lt;125</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.53 ± 0.02</td><td>N</td></tr></tbody></table>
<figure><img src="image_4.png" /><figcaption>**Figure 2.** All spectra for four of the targets in this survey, each normalized by a low-order polynomial function. Vertical lines indicate the $H\alpha$ (long black line), the 6300-Å [O I], 5876-Å and 6678-Å He I emission lines (long grey lines) and the 6707-Å Li photospheric absorption line (short grey lines). The gap around 6900 Å corresponds to a region of poor atmospheric transmission within which data quality is severely affected. In a few cases, the polynomial fit was imperfect, resulting in an incorrect continuum slope (e.g. CZ Tau on 2009 November 23).</figcaption></figure>

# 4 RESULTS

## 4.1 Raw emission line measurements

The primary spectral feature studied here is the $H\alpha$ emission line, which is detected in all spectra of all sources. In order to derive its EW and $W_{10}$, the continuum was interpolated linearly from surrounding spectral regions before the wavelengths marking the limits of the emission line were estimated. The line EW and $W_{10}$ were then directly measured using linear interpolation in the wings of the line. Raw (measurement) uncertainties were estimated by allowing the line boundaries to vary within conservative ranges. Uncertainties on the line EW are of the order of 2 per cent, albeit with a ‘floor’ uncertainty of 0.1 Å for the weakest lines. Typical uncertainties on $W_{10}$ range from 5 to 20 km s$^{-1}$. The EW of several other emission lines, listed in Section 2.1, as well as the EW of the Li 6707-Å absorption line, were measured using the same method; the results are reported in Table 3. All these emission lines are always weak and spectrally unresolved in our spectra.

The $W_{10}$ estimates we obtained are subject to instrumental effects, the most immediate of which is line broadening owing to the limited spectral resolution of our data. In order to correct for this effect, we assume that the convolution of the intrinsic stellar spectrum by the instrumental spectral response readily translates in a quadratic sum of the line widths for both their FWHM and $W_{10}$. Implicitly, the underlying hypothesis is that both the intrinsic emission line profile and the instrumental response can be approximated

by Gaussian profiles. The spectral profile of isolated lines in the spectra of arc lamps supports this assumption, and we use these profiles to evaluate $W_{10}^{\text{inst}}$. Emission lines in the spectra of TTS, on the other hand, can be complex and depart from simple Gaussian profiles, particularly in the case of $H\alpha$. Nonetheless, in the case of relatively narrow lines ($W_{10} \lesssim 200$ km s$^{-1}$), this is a reasonable assumption, and thus our approach is validated. In cases where the line is intrinsically much broader, the broadening induced by the instrumental resolution is small, and so a departure from a Gaussian line profile has limited consequences on the measured $W_{10}$. We then proceed to quadratically subtract $W_{10}^{\text{inst}}$ from all the raw $W_{10}$ estimates in order to correct them for instrumental line broadening. If the raw estimate of $W_{10}$ is lower than $W_{10}^{\text{inst}}$, therefore precluding this approach, we place an upper limit on the intrinsic $W_{10}$ by generating 100 000 random generalizations of both quantities according to their associated uncertainty and adopt the 99.7th percentile of the resulting distribution of instrument-corrected $W_{10}$ estimates as $3\sigma$ upper limits.

## 4.2 Precision and accuracy of the line measurements

As a consequence of our limited spectral resolution and spectral sampling, ambiguity in setting the continuum and the presence of photospheric absorption features limit the accuracy of our line measurement. In particular, photospheric features can result in
the continuum level being set slightly lower than it ought to be. As a result, our methodology leads to slight overestimates of the line EW, albeit at levels that do not exceed our uncertainties. On the other hand, the bias introduced on the $W_{10}$ estimates can be significant. This bias is more severe than that of EW, as it depends on the detailed shape of the wings of the line profile, which is particularly delicate to assess. This issue is particularly apparent in cases where some (or all) of the following conditions are met: (1) the emission line is both weak and narrow, leading to a low peak/continuum ratio; (2) the target has a late spectral type, whose spectrum is extremely rich in broad, molecular photospheric features that can affect the continuum evaluation; and (3) the spectral resolution is at the low end of the range used in this study. In order to help alleviate this last problem, we have systematically overplotted our highest-resolution spectrum of a target over the lower-resolution spectra as a template in order to better evaluate the intrinsic underlying photospheric spectrum. This procedure still gives larger uncertainties in the case of the lower-resolution spectra, but it helped to minimize the systematic bias that could arise from misinterpreting a nearby absorption line for part of the emission line.

In order to address the first two issues listed above, we generated simulated spectra to test the precision and accuracy of our measurement method. The simulations measured the effect of our instruments on spectral templates taken from the MILES stellar library (Sánchez-Bláquez et al. 2006) for 12 stars that cover the mid-K to late-M spectral-type range. The simulation proceeded in four steps: constructing the Gaussian response profile of each instrument using the measured instrumental $W_{10}$; adding an $H\alpha$ emission line to the template spectrum (which naturally contains a weak absorption line); convolving the two profiles to render the simulated outcome; and applying adequate instrumental sampling to the result. The emission lines were assumed to have Gaussian profiles centred on $H\alpha$, with our choice of parameters reflecting our interest in lines that are both narrow and weak. Specifically, we produced synthetic spectra with all possible combinations of three EWs (0.5, 2 and 5 Å) and six $W_{10}$ (ranging from 150 to 400 km s⁻¹ in 50 km s⁻¹ increments). With six instrumental set-ups, we thus built a library of 1080 distinct simulations. The reduction pipeline described in Section 3 was then applied on each synthetic spectrum to measure the $H\alpha W_{10}$, which we then compared with our input parameters to assess the amplitude of the bias introduced by our medium spectral resolution.

The overall results from this battery of simulations matches our expectations and can be summarized as follows.

(1) Lower-resolution spectra result in larger uncertainties, as well as less constraining upper limits.

(2) Emission lines with $W_{10} \ge 300$ km s⁻¹ are broad enough (and, in practice, strong enough) that there is only a negligible bias, even though this bias introduces an additional uncertainty of 12–18 km s⁻¹ depending on the instrumental resolution.

(3) Narrow emission lines that have EW $\ge 5$ Å suffer from an essentially linear bias but are strong enough that the details of the underlying continuum (i.e. spectral type) have a negligible impact on this bias, which depends only on $W_{10}$ and instrumental resolution.

(4) Narrow and weak emission lines are most susceptible to this bias, although the largest effect introduced by the instrumental correction is to increase the uncertainty associated with the final estimate of $W_{10}$. Both the bias and its associated uncertainty are increased for later spectral types owing to the richer nature of the photospheric spectrum.

<figure><img src="image_5.png" /><figcaption>**Figure 3.** Bias on the $H\alpha W_{10}$ (i.e. difference between the intrinsic and derived $W_{10}$ values) derived from our simulations. Symbols with error bars represent the median and standard deviations of subsets of our simulations, grouping the two highest and two lowest spectral resolutions for better statistics. The lines represent our best estimate of the bias introduced by the medium resolution of our spectra for strong lines in any K- or M-type star (solid) and weak lines in mid-M targets (dashed). The filled bands represent our $1\sigma$ confidence interval for three representative cases: strong line in any K- or M-type target observed at the higher resolution (dark grey) and the lower resolution (grey), and weak line in a mid-M target observed at the lower resolution (light grey). Other combinations of line strengths, target spectral type and spectral resolution were also explored but are not shown for reasons of readability. The dark and light grey bands represent the extreme cases of our entire set of simulations.</figcaption></figure>

Fig. 3 illustrates quantitatively the results of our simulations. For an intrinsic $W_{10}$ of 200 km s⁻¹, the amplitude of the bias is of the order of 20 km s⁻¹, with uncertainties ranging from 12 to 30 km s⁻¹, depending on line strength, spectral type and spectral resolution. Therefore, although this bias could have some consequences for the accretion classification of individual spectra, our simulations confirm that the premise of our analysis, namely that we can derive the intrinsic $W_{10}$ of the $H\alpha$ line with our medium-resolution spectra with sufficient accuracy considering the range of expected line widths, is sound. We thus proceed to correct all of our derived $W_{10}$ from this bias using linear fits to the results of our simulations, and to increase their associated uncertainties. Typical amplitudes for both effects are illustrated in Fig. 3. As a result of this process, we also had to place upper limits on $W_{10}$ based on the lowest line width that can be confidently retrieved in our simulations. These upper limits range from 125 to 200 km s⁻¹, depending on the instrumental resolution.

We further tested the robustness of the bias correction described above using our own data. We first selected 11 targets spanning the overall ranges of spectral type and $H\alpha$ EW and $W_{10}$ observed in our sample. For each object, we selected a spectrum from our highest-resolution setting, and degraded it to the resolution and spectral sampling of our other instrumental set-ups (excluding the low-resolution WHT/ISIS set-up). We then proceeded to measure the raw $W_{10}$ of the $H\alpha$ line, and to correct for both the instrumental broadening and methodological bias. Comparing the results for $W_{10}$ with those initially measured in the higher-resolution spectrum, we find that the results are within $1\sigma$ of each other in 20 out of 33 cases, and within $2\sigma$ of each other for all but two spectra. These exceptions correspond to the broadest $H\alpha$ lines we tested ($W_{10}=550–650$ km s⁻¹) when the spectra are degraded to the lowest-resolution (SPM) setting. Overall, these tests confirm that our approach takes
<figure><img src="image_6.png" /><figcaption>**Figure 4.** *Left:* Comparison of the mean Hα EW from our survey with previously published estimates (see Table 1) for all objects in our sample. Vertical uncertainties represent the standard deviation from all measurements of a given object. The dotted and dashed lines mark the identity relationship and an unconstrained least-squares linear fit to all objects, respectively. *Right:* Comparison of the W₁₀ Hα measurements from our survey with previously published estimates (White & Basri 2003; Nguyen et al. 2012). From our monitoring campaign, we plot the weighted mean and the largest of (1) the standard deviation of all measurements for a given target and (2) the uncertainty associated with the weighted mean. Symbols are as in Fig. 1. For objects with too few estimates of W₁₀, we show the median of all measurements and the upper limit from our survey. The dotted line marks the identity relation to guide the eye, whereas the dashed line is the result of a linear fit to objects with W₁₀ ≥ 250 km s⁻¹.</figcaption></figure>

<figure><img src="image_7.png" /></figure>

proper account of the effects introduced by the medium resolution used in the survey.

## 4.3 Comparison with previous measurements

Before combining our data sets for individual objects with an unexpected accretion state, we first present an overview of the results by comparing our measurements of both the EW and W₁₀ of the Hα line with those listed in the literature (White & Basri 2003; Nguyen et al. 2009). For each star in our sample, we compute the uncertainty-weighted average of both quantities. With these mean quantities, we associate an ‘uncertainty’, which is the largest of (1) the dispersion of all values and (2) the uncertainty on the weighted average. In practice, for all EW and most W₁₀, the former is larger than the latter. For some objects, most (or all) of our spectra led to an upper limit on W₁₀. In these cases, we assigned an upper limit to the object that is the median of all measurements and upper limits. Fig. 4 shows a comparison of our average measurements with literature data.

Some objects show significant departures from the unity relationship, which are indicative of significant long-term variability. This effect could at least partially explain some of the apparently passive disc systems, as the Hα EW has been underestimated in past studies of some of our targets. Furthermore, our EW values are lower by ~15 per cent on average relative to literature measurements, which we suspect is a result of the lower spectral resolution of those earlier EW-driven studies, which leads to biased estimates of the continuum level. Nonetheless, the strong correlations between our measurements and previous ones are statistically very significant (at the ≥3σ and ≥7σ levels for W₁₀ and EW, respectively, using either the Spearman or Kendall tests). The slopes of the linear fits are 0.92 ± 0.05 and 1.66 ± 0.31 for the EW and W₁₀ measurements, respectively (including only objects with W₁₀ ≥ 250 km s⁻¹ for the latter fit); that is, both fits are consistent with the 1:1 relationship within ~2σ. Because most of the literature data used to make these plots were obtained several years ago, we conclude that the average Hα EW and W₁₀ of TTS do not change dramatically over such timescales. For instance, the median difference between our average W₁₀

value and that from the literature is −5 km s⁻¹, with a dispersion of 67 km s⁻¹.

## 4.4 Timescales of line variability

As noted above, the dispersion of values we find for both the Hα EW and W₁₀ is much larger than the uncertainty associated with each individual measurement. Focusing on W₁₀, the largest epoch-to-epoch fluctuation is significant at the ≥2σ (3σ) level for 22 (17) out of the 27 objects with two or more measurements (i.e. excluding upper limits). The most significant differences exceed the 9σ confidence level. While the five remaining systems have non-significant variations (≤1σ), we obtained only two or three W₁₀ estimates for each of them. Furthermore, four of these five objects are not accreting (see Section 4.5), and we expect non-accreting objects to have line profiles that are more stable. Overall, the large dispersion of W₁₀ estimates for most targets illustrates the long-established strong variability of the line profile on time-scales as short as 1 d. Nonetheless, the dispersion in W₁₀ that we measure is comparable to previous dispersion estimates for the same targets (e.g. Nguyen et al. 2009), with a median ratio of 1.4 and with most systems below a ratio of ~2. This suggests that the amplitude of fluctuations of W₁₀ does not increase dramatically beyond the ~1-yr time-scale of individual studies.

The sampling of our monitoring campaigns allows us to probe a wide range of time-scales, from 1 d to 1 yr, thus complementing the above analysis which addresses multiyear time-scales. Specifically, we evaluate the epoch-to-epoch variation of both quantities for each pair of observations of a given target, leading to up to 55 independent EW or W₁₀ differences per source. We then group all the resulting differences by bins of time delay: ~1, 2–4, 6–12, 14–28, 30–60 and 300–360 d. These bins correspond to natural breaks in our campaign sampling. They also allow an inspection of the degree of line variability on time-scales of days, weeks, months and 1 year. Because the EW values span such a large range over our entire sample (from ≲1 to ≥100 Å), and because accreting TTS have systematically much larger EWs than non-accreting TTS, we focus on the relative differences in EW.
<figure><img src="image_8.png" /><figcaption>**Figure 5.** Left: Difference in equivalent width (EW) (relative to the median EW over all epochs) as a function of time interval for all objects in our sample. Green diamonds, red triangles and blue squares represent accreting, non-accreting and disc-less objects (only UX Tau C belongs to the latter category), respectively; they are separated horizontally for display purposes only. In order to minimize confusion, we binned the data using the vertical grey lines to mark the bin separations, which correspond to natural breaks in our temporal coverage. In each bin, we show the median, 68th and 90th percentiles as the horizontal segment, rectangular box and whiskers, respectively. The most extreme outliers are shown as individual data points. In cases where fewer than 10 objects were available in a bin, we plot all individual measurements as separate symbols instead. Right: Difference in $W_{10}$ as a function of time interval for all accreting objects in our sample. We have too few $W_{10}$ detections for non-accreting and disc-less objects (four objects with two measurements each). Symbols are the same as in the left panel. The numbers of pairs of measurements included in each bin are indicated at the top.</figcaption></figure>

Fig. 5 summarizes the variability of both the H$\alpha$ EW and $W_{10}$ over all time-scales covered in this study. Here we group objects based on their accretion status, which is derived in Section 4.5. The first immediate observation is that accreting TTS display a much wider amplitude of variability in EW, with epoch-to-epoch variations sometimes exceeding a factor of 3 change in line intensity, compared with non-accreting TTS, which do not exceed 70 per cent epoch-to-epoch fluctuations. Combining all time-scales, a Wilcoxon rank-sum test confirms at the 5.4$\sigma$ confidence level that accreting TTS experience a higher median degree of variability than non-accreting objects. This difference in amplitude of variability between accretors and non-accretors is statistically significant on time-scales longer than 1 month, and there is marginal evidence that it may extend down to time-scales of 1 week. Our observing cadence results in a poorer sampling of shorter time-scales. On the other hand, non-accreting and disc-less objects share similar variability properties over all time-scales within uncertainties.

Only accreting TTS yield enough $W_{10}$ measurements to enable the variability of this quantity to be probed: we could measure $W_{10}$ (rather than obtaining an upper limit) for two epochs for only 4 of our 11 non-accreting or disc-less targets. We thus focus on accreting TTS when studying $W_{10}$ variability. First of all, we note that the amplitude of variations in $W_{10}$ can be large: the 95th percentile exceeds 150 km s$^{-1}$ over all time-scales longer than 1 d, to be compared to a median $W_{10}$ of 410 km s$^{-1}$ over all accreting targets. However, both the upper envelope to the distribution and its 95th percentile are independent of time-scale. A uniform degree of variability over all time-scales longer than 1 d is consistent with the results of Nguyen et al. (2009) and Costigan et al. (2014). Our sampling does not provide sub-day coverage, for which the noted authors found that the variability amplitudes are reduced.

On the other hand, we notice a gradual increase in the median $W_{10}$ difference with longer time-scales: it increases from 34 to 43 and to 77 km s$^{-1}$ for time-scales of less than 1 month, 1–2 months and 1 yr. Computing similar median differences in $W_{10}$ from the data shown in Nguyen et al. (2009) (their fig. 3), we find median differences of 34, 46 and 27 km s$^{-1}$ over the same time-scales, respectively. On

time-scales up to 2 months, both studies yield consistent results, confirming the robustness of the gradual increase. On the other hand, the much reduced difference in $W_{10}$ on a time-scale of 1 yr in Nguyen et al. (2009) is opposite to the results from our survey. However, we note that the 2010 part of our campaign was focused mostly on non-accreting TTS, so that very few measurements for accreting TTS contribute to the long-time-scale bin (nine individual $W_{10}$ measurement covering five targets). As a result, the influence of a handful of lower-than-average $W_{10}$ is amplified by our computing differences from all possible pairs. Of the five objects contributing to this bin, only UX Tau A's lone 2010 observations represent a significant outlier compared with its 2009 observations, but that particular spectrum is characterized by a strong inverse P Cygni profile that accounts for the low apparent $W_{10}$ (see Fig. 6). We thus do not consider that the apparent contradiction on the 1-yr time-scale between our results and those of Nguyen et al. (2009) represents a meaningful difference.

## 4.5 Accretion status

The next step in our analysis consists in determining which objects were actively accreting during our observations and when. Because we want to test the robustness of the H$\alpha$-based criterion, we must rely as much as possible on other tracers in our spectra. Specifically, for each spectrum of each object, we classified the object as accreting if at least one the following conditions was fulfilled: (1) the H$\alpha$ line profile shows unambiguous asymmetry (double peak, broad red- or blue-shifted 'shoulder', P Cygni profile); (2) either of the two He I lines is detected in emission; (3) at least one line of the Ca triplet is detected in emission; and/or (4) the EW of the Li 6707-Å absorption line is significantly different from the weighted average of all other detections for that source. Because of the lack of spectro-photometric quality and the limited set of template spectra from non-accreting objects, our data do not provide a robust estimate of the veiling, so we use the latter condition as a proxy for measuring a change in continuum veiling.

If none of these four conditions is fulfilled, it is tempting to consider the object as non-accreting at that epoch. However, there
<figure><img src="image_9.png" /><figcaption>**Figure 6.** Example of continuum-normalized spectra for remarkable sources in our sample, illustrating the large variability in line profile and/or strength. For reference, the horizontal grey bar represents 200 km s⁻¹ at the wavelength of H α.</figcaption></figure>

are reasons to adopt a more cautious approach. First of all, some of our spectra do not include the He I 5876 nor the Ca triplet, which are among the strongest lines in accreting TTS. Furthermore, even these lines remain undetected in objects whose accretion status is established by UV/blue excess emission (e.g. Alcalá et al. 2017). Similarly, when the H α line profile is relatively narrow, medium-to-weak profile asymmetries may remain undetected at our spectral resolution. Finally, our precision in measuring the Li 6707 EW (typically ranging from 0.05 to 0.15 Å) is sufficient to detect only strong variability in accretion-induced veiling. Indeed, veiling in the red optical is undetected even in confirmed accretors (e.g. Frasca et al. 2017). As a result, it is possible that a spectrum in which none of the four conditions listed above is fulfilled is nonetheless associated with an accreting TTS. In order to resolve this ambiguity, we adopted the following method: if no condition is fulfilled in any spectrum of a given target, the object is considered as non-accreting throughout our survey. We caution that it remains possible that these objects are accreting at low enough accretion rates that no tracer is detectable in our spectra, but we consider it unlikely that this is true for all epochs on a given target. If, on the other hand, the object is distinctively accreting at some epochs, but remains ambiguous at others, the accretion status for the latter is based on the H α EW and W₁₀: the objects is considered ‘probably accreting’ (marked as ‘Y?’ in the 9th column of Table 1) at epochs when the line is at least as strong and/or wide as it was at clearly accreting epochs.

In our sample, there are 11 objects that are unambiguously accreting at all epochs. Unsurprisingly, all but one of them are part of our control sample of accretors. The lone exception is IQ Tau,

which belongs to the candidate passive disc subsample. As illustrated in Fig. 6, the H α line profile for this object is markedly double-peaked at multiple epochs, leaving no doubt about its accretion status. Conversely, five objects appear to be never accreting in our survey. Four of them belong to our candidate passive disc subsample (CoKu Tau 4, FW Tau, RX J0432+1735 and V819 Tau), and thus our data confirm that those objects show no sign of accretion over time-scales ranging from 1 d to at least 1 yr.

A group of 14 targets show a common behaviour of unambiguously accreting at multiple epochs and ‘probably accreting’ at all other epochs. For lack of contradictory evidence, we surmise that these objects were continuously accreting throughout our survey. This group includes two candidate passive discs. HQ Tau has a consistently weak but broad, and often double-peaked, H α line. It is therefore a textbook example of a TTS whose line profile is strongly affected by strong self-absorption, resulting in an uncharacteristically low EW (Fig. 6). UX Tau A displays a similar behaviour, with a marked inverse P Cygni profile. The other candidate passive disc that we find to be actually accreting is V836 Tau. This is an example of a system for which at least one historical EW measurement is much weaker than those measured in our spectra (18–75 Å). The original measurement is from Mundt et al. (1983), who noted significant line variability. Intense line variability is evident in our data for this source, with a strong accretion outburst observed on 2009 October 31 (Fig. 6). In the absence of the original spectra from Mundt et al. (1983), it is unclear whether the low-EW epochs are the consequence of line self-absorption or an actual pause in the accretion flow onto the central star. In any event, the detection of He I
<figure><img src="image_10.png" /><figcaption>**Figure 7.** *Left:* Spectral energy distributions (SEDs) for all objects possessing a circumstellar disc but identified as non-accretors in our survey, with the exception of CZ Tau. The grey spectrum is the 3200 K NextGen stellar model (Allard et al. 1997), while the dot-dashed curve is the SED for the 'median' Taurus Class II source (Mathews et al. 2013). All SEDs are normalized to their *J* (1.25 µm) flux for ease of comparison. *Right:* SED for CZ Tau compared with the four targets in our sample that possess a disc and have a spectral type within a half subclass of that of CZ Tau. Curves and normalization are as in the left panel. As expected, the accreting Class II sources scatter around the median SED, whereas CZ Tau lies an order of magnitude higher in the mid-infrared.</figcaption></figure>

emission lines unambiguously establishes this object as accreting in our survey.

One unexpected member of this group is MHO 4, a disc-less object that is not expected to undergo accretion at all. However, one the He\i lines or the other is detected at four epochs, a fact that was also noted in the discovery study of Briceño et al. (1998). This leads to an ambiguous interpretation for this source. Either it possesses a circumstellar disc that has so far escaped detection even at mid-infrared wavelengths (Luhman et al. 2010), or the emission lines instead originate in the surrounding cloud, and this extended emission is not perfectly subtracted in the usual sky-subtraction in long-slit spectra. In the absence of conclusive evidence pointing either way, we consider this object as a likely non-accretor but do not include it in any statistical test, in order to avoid any bias.

FP Tau is the only object in our survey that has one epoch with an apparently weak $H\alpha$ line compared with the other epochs and no other accretion tracer. While it is possible that this object experienced a short pause in accretion, we note that its $H\alpha$ line is only marginally weaker than at other epochs, and thus we consider it more likely that it is continuously accreting. We list its accretion status as 'Y?' in Table 1.

Finally, two objects (CZ Tau and V410 Tau X-ray 6, both candidate passive discs) would be unambiguously characterized as non-accretors in our survey except for the fact that we detect significant [OI] emission at multiple epochs. This is puzzling, because the line is usually a tracer of outflow, which itself requires active accretion onto the central star. Therefore the origin of this emission line in these objects is uncertain. In addition to the possibility of contamination by improperly corrected atmospheric airglow and/or background emission from the surrounding molecular cloud, we note that CZ Tau is an unresolved and unusual binary system, which possibly accounts for the line emission pattern (see Section 5.1). Based on all other emission lines, we classify both objects as 'probably not accreting'.

# 5 DISCUSSION

## 5.1 Passive discs and flickering accretion in Taurus

Overall, we have identified seven non-accreting objects in our sample. In particular, six out of the nine candidate passive discs are

confirmed to be non-accretors. The remaining three sources in that sample either masqueraded as weak $H\alpha$ emitters whose broad line revealed their true nature (HQ Tau), or display a strongly variable line strength, with peak-to-trough ratios exceeding a factor of 4 (IQ Tau and V836 Tau). As it turns out, the historical EW measurements of these latter two sources were obtained at epochs of weak line emission, which accounts for their initial classification. Unfortunately, these historical measurements do not have corresponding $W_{10}$ estimates, so it is impossible to decide whether they were accreting or not at that time. The only robust statement we can make is that those objects were consistently accreting throughout our monitoring campaign. Weeding out such objects from our initial sample of candidate passive discs was one of the goals of our project.

Taken at face value, our campaign confirms the passive disc nature of the six objects with a confirmed disc but no sign of accretion. However, all but two of these objects are instead transition discs (CoKu Tau 4 and V410 Tau X-ray 6; Luhman et al. 2010) or have extremely weak IR excesses and, thus, are best characterized as young debris discs (V819 Tau and RX J04328+1735; Furlan et al. 2009; Wahhaj et al. 2010; Hardy et al. 2015). None of these objects has an infrared excess out to ~10 µm (Fig. 7), indicating an absence of dust in the inner $\gtrsim 1$ au. The apparent absence of accretion on the central star is therefore not surprising.

The remaining two objects are cases in which interpretation is muddled by multiplicity. FW Tau is a triple system in which the lone circumstellar disc is associated with a substellar component (Kraus et al. 2015), whereas the optical spectra are dominated by the close pair consisting of two disc-less WTTS. CZ Tau is a close (0.3 arcsec) binary system whose SED is not typical of Class II objects. Fig. 7 shows that, compared with other Class II sources with similar spectral types in our sample, CZ Tau is characterized by a remarkably strong mid-emission. Indeed, the bolometric luminosity of the system is actually dominated by the mid-infrared emission from the system rather than by the near-infrared. While such a double-hump shape is often associated with edge-on disc systems, CZ Tau is not under-luminous as is typical for these special systems. Instead, CZ Tau is a member of the small category of 'infrared companions' (Chelli et al. 1988; Koresko, Herbst & Leinert 1997), as further confirmed by the strongly wavelength-dependent flux ratio observed by McCabe et al. (2006). Therefore,
this is another case where the optical light, which indicates no accretion, is associated with a different component from the infrared emission, which reveals the presence of a disc.

In summary, our search for permanently non-accreting full-fledged discs has led to a null result. While the existence of passive discs has long been suggested, it appears that a sufficiently detailed scrutiny of each individual object rules out this particular configuration, at least in the Taurus star-forming region. Instead, the 5–10 per cent occurrence rate suggested by large surveys (e.g. McCabe et al. 2006; Hernández et al. 2014; Pettersson, Arround & Reipurth 2014) is probably the result of a combination of transition discs, debris ('anemic') discs, and weak-but-broad-line impostors in these regions.

On the other hand, the (presumably less evolved) pre-transitional discs in our sample, LkCa 15 and UX Tau A, which are characterized by a mid-infrared deficit but significant near-infrared excess, were accreting at all epochs. In other words, discs that extend inwards to the immediate vicinity of the star always support ongoing accretion onto the central objects. In turn, this implies that the disc clearing process is essentially simultaneous, in the sense that dust is cleared out as soon as the accretion flow is halted (or vice versa). From a physical standpoint, the implication is that it is virtually impossible to prevent a significant amount of material from accreting onto the central star, suggesting that the viscous evolution of the inner disc always dominates the dynamical state of the inner disc, irrespective of the how the accretion flow is initially sustained.

A second goal of the survey was to identify objects whose accretion was flickering, namely TTS that appear to be accreting sometimes but not always. Focusing first on objects whose Hα EW temporarily crosses the spectral type-dependent threshold for accretion, a method that has been used in the past to suggest flickering accretion (e.g. Murphy et al. 2011; Riviere-Marichalar et al. 2015), we found eight such objects in our survey. Of these, six have a broad line as measured by their W₁₀, and thus the apparently weak line is induced by self-absorption rather than by a pause in accretion. The remaining object is DN Tau, whose Hα EW hovers around the threshold, but which has multiple detections of the He I 5876 emission line. The accretion status of this object was independently confirmed by spectropolarimetry (Donati et al. 2013). We interpret this object as an example of the ambiguous nature of any Hα-only criterion.

In conclusion, we did not identify any object that unambiguously experienced a temporary pause in accretion during the course of our monitoring survey, suggesting that such events are rare. Limiting the analysis to the 24 accreting objects with multiple observations in our survey, we obtained a total of 158 spectra. This implies an upper limit of 2.2 per cent (95 per cent confidence level) for the duty cycle of accretion 'gaps' in TTS, assuming all stars undergo such events. No definitive example of a complete halt to the accretion flow on a young star has been identified yet, although large variations in accretion rates, traced both by line strength and by indirect evidence of the accretion column passing in front of the star, have been recorded in the case of AA Tau (Bouvier et al. 2003, 2007b). The inherent stochastic variability of this and similar systems precludes determining precisely the duty cycle of such a phenomenon. However, the stringent upper limit on the duty cycle derived here may be so low that it would make it unlikely that such an event would be detected for any single object. In turn, this would imply that only objects in a particular state of evolution, possibly those close to disc dissipation, can experience accretion 'gaps'.

## 5.2 On the use of Hα as an accretion discriminator

The monitoring campaign that we have conducted allows us to revisit in more depth the usefulness of the traditional criteria based on the Hα emission line to assess the accretion status of TTS.

First of all, we notice that the Hα EW is over the spectral type-dependent threshold proposed by Barrado y Navascués & Martín (2003) in 83.5 per cent (respectively 79.6 per cent) of all individual spectra of confirmed (respectively likely) accretors. The corresponding fraction of spectra for which W₁₀ exceeds 200 km s⁻¹ is 95.0 per cent (respectively 89.6 per cent). In other words, roughly 10 per cent and 20 per cent of individual observations would lead to an incorrect classification based only on the W₁₀ and on the EW criterion, respectively. In other words, the discriminative power of traditional Hα-based criteria is strong but imperfect. While the fractions quoted above could be biased owing to the make-up of our sample, they provide a reasonable order-of-magnitude estimate of the error rate of these criteria. Because the initial reconnaissance of new, large young stellar populations still often relies on low- to medium-resolution optical spectroscopy for practical reasons, it is important to understand the limits inherent in the traditional Hα criteria. In particular, while the EW criterion has a relatively uniform misclassification rate as a function of spectral type, the W₁₀ criterion correctly senses accretion in less than two-thirds of all objects with a spectral type later than M3. We revisit this issue below.

In order to place our results in a broader context, we have assembled a large sample of TTS with measured Hα EW and/or W₁₀ from the recent literature, specifically using the results from Cieza et al. (2010, 2012), Costigan et al. (2012), Nguyen et al. (2012), Manara et al. (2013), Alcalá et al. (2014) and Frasca et al. (2015). In each of these studies, the accretion status of each object was determined based on both W₁₀ estimates and the presence of other emission lines, essentially following the same methodology as we have used. We are interested in probing possible dependences on stellar mass, but this quantity has not always been estimated in these studies. Because deriving the mass of TTS is a model-dependent proposition based on placing the stars in the Hertzprung-Russell (HR) diagram (e.g. Hillenbrand & White 2004), the ideal approach would be to use a uniform method to derive the masses of all objects considered here. However, the availability of the necessary photometry and spectral information is far from uniform, leading to uncertainties. Furthermore, the impact of the detailed accretion history, activity, rotation and magnetic field on the location of TTS in the HR diagram may be greater than previously thought (Baraffe, Vorobyov & Chabrier 2012; Somers & Pinsonneault 2014; Jackson & Jeffries 2014; Bouvier et al. 2016). While we cannot escape these issues, we decided to use the stellar masses adopted in the studies referred to above whenever available. In all other cases, including for our sample, we used for convenience the relationship between spectral type and stellar mass proposed by Kirk & Myers (2011), which assumes a common system age of 1 Myr for all targets. While uncertainties of the order of 50 per cent are introduced, we are confident that the qualitative trends (or absence thereof) that we find in our analysis are robust. However, we stress that uncertainties on quantitative trends, particularly dependences on stellar mass, should be treated with caution.

Let us first consider the Hα EW, illustrated in the left panel of Fig. 8. While the criterion proposed by Barrado y Navascués & Martín (2003) marks the approximate transition between accretors and non-accretors, the upper envelope of the non-accretors lies significantly above the lower envelope of the accretors, by up to a
<figure><img src="image_11.png" /><figcaption>**Figure 8.** Left: Hα Equivalent width (EW) measurement as a function of stellar mass for T Tauri stars. Blue and red stars indicate the weighted average (excluding upper limits) for accreting and non-accreting objects in our sample, respectively. Open symbols represent samples of WTTS, CTTS and transition discs in multiple star-forming regions taken from the literature (squares: Cieza et al. 2010, 2012; down-pointing triangles: Costigan et al. 2012; diamonds: Nguyen et al. 2012; up-pointing triangles: Manara et al. 2013; Alcalá et al. 2014; crosses: Frasca et al. 2015). Dark green and orange symbols distinguish accreting from non-accreting objects, the classification is taken from these studies. The dashed and dotted curves represent the EW accretion criterion of Barrado y Navascués & Martín (2003) and 20 times that value, respectively. Right: $W_{10}$ Hα measurements as a function of stellar mass and spectral type for T Tauri stars. Symbols are the same as in the left panel. Objects for which only upper limits were obtained in most epochs are shown as upper limits. The dot-dashed curve represents $1.5v_{\text{ff}}$ based on interpolated stellar radii from Siess, Dufour & Forestini (2000) and assuming free-fall from a distance of $5R_*$. The dashed line is the result of a log-linear fit to all accretors.</figcaption></figure>

factor of ~2. In other words, there is no definitive EW discriminat-
ing threshold between accretors and non-accretors, as we already
pointed out from our own data set. As illustrated in our survey, ob-
jects with a weak, but broad, Hα line underline the importance of
medium-to-high-resolution spectroscopy. Conversely, intense flares
in disc-less but chromospherically active TTS have occasionally led
some stars to cross the traditional accretion threshold (e.g. Riviere-
Marichalar et al. 2013). While this has been pointed out in the
past (e.g. Fang et al. 2013), this analysis confirms that there is a
‘grey area’ of overlap between accretors and non-accretors based
on the Hα EW. This does not mean that previous criteria are poor:
only about 2 per cent of all non-accretors have an EW that exceeds
the threshold proposed by Barrado y Navascués & Martín (2003),
while about 13 per cent of all accretors fall below it. Therefore, both
the purity and completeness of this criterion are high, and it is very
likely to yield the correct classification for any one object. However,
applying it for a large sample is liable to produce a small number
of incorrectly classified objects, especially bona fide accretors mas-
querading as non-accretors. As an aside, we note that the EW upper
and lower envelopes for accretors follow the same shape, indicating
that the range of line EW is independent of stellar mass, and hence
of luminosity.

Similarly, we plot $W_{10}$ as a function of stellar mass for the same
samples from the literature in the right panel of Fig. 8. Focusing first
on the non-accretors, we find no significant dependence of their $W_{10}$
on stellar mass, with a median value of ~130 km s⁻¹. A handful
of objects have much broader lines, up to ≳400 km s⁻¹, but these
are either known or suspected spectroscopic binaries, for which
line broadening is induced by the blending of two lines that are
shifted as a result of orbital motion (e.g. Manara et al. 2013). The
90th and 95th percentiles (205 and 245 km s⁻¹, respectively) are
in line with the previously proposed upper limits (200–270 km s⁻¹,
White & Basri 2003; Natta et al. 2004). However, we emphasize
that, once a sufficiently large sample is gathered, no clear upper
cut-off in the $W_{10}$ associated with chromospheric activity appears,
so that outlier non-accretors can overlap with accretors in $W_{10}$. This

is especially true for the lower-mass objects, with $M \lesssim 0.5$ M$_{\odot}$, whereas a cleaner gap exists for $M \gtrsim 1$ M$_{\odot}$. This is in line with our finding that later-type stars often have narrow H$\alpha$ lines but are clearly accreting based on other emission lines.

In summary, this analysis confirms that the Hα line alone is an
imperfect discriminator of accretion in TTS. Even the use of $W_{10}$
measurements, which has taken a more prominent role in recent
years, is insufficient to assess definitely the accretion status of a
given object, especially if its mass is ≲0.5 M$_{\odot}$. On the other hand,
the discriminative power of $W_{10}$ is much higher for $M_* \gtrsim 1$ M$_{\odot}$.
Interpreting occasional outliers from large-scale low-resolution op-
tical surveys, the usual first step in characterizing a new, distant
star-forming region, is therefore fraught with ambiguity and should
be done with great caution.

## 5.3 Hα as a quantitative tracer of the mass accretion rate for TTS

### 5.3.1 Ensemble correlations

Many attempts have been made to convert the Hα line properties
into an estimate of the accretion rate on the central star. While these
efforts have not been very successful for the EW because of other
contributions to the line emission (e.g. Antoniucci et al. 2011), Natta
et al. (2004) first noted that the line $W_{10}$ is well correlated with the
accretion rate, a conclusion supported by Herczeg & Hillenbrand
(2008) albeit with a different quantitative relationship. Here we use
the results of our survey, both at an ensemble level and through
temporal variations for individual objects, to revisit this conclusion.

We first focus on the time-averaged $W_{10}$ measurements for ac-
cretors and find that a significant correlation with stellar mass is
evident in Fig. 8. For instance, a Spearman rank correlation test
returns a false alarm probability (i.e. the probability that the quan-
tities are not correlated) of $p < 6.3 \times 10^{-10}$. Assuming a simple
log-linear fit ($W_{10} = \alpha + \beta \log(M_*)$), the ensemble of all accretors
is characterized by $\beta \approx 125$ km s⁻¹ dex⁻¹, with an intrinsic scatter
of ~85 km s⁻<fnref n="1" /> that is independent of stellar mass. In order to evaluate the influence of our mass-determination method, we repeated the same fit using only stars for which stellar masses were derived from placing the stars in the HR diagram in previous studies. This yields a very similar slope of $\beta \approx 130$ km s⁻<fnref n="1" /> dex⁻<fnref n="1" />, confirming that our simple method to estimate stellar masses does not introduce significant biases in this correlation.

In order to interpret this correlation, it must be kept in mind that correlation does not imply causation. In particular, separate correlations with a 'hidden' third quantity could explain the observed correlation between stellar mass and average $W_{10}$. A quantity that could naturally play such a role is the stellar accretion rate, which has been found to correlate with both stellar mass and $W_{10}$. The stellar accretion rate has been found to follow a $\dot{M}_{\text{acc}} \propto \dot{M}_*^2$ relationship (see Hartmann et al. 2016, for a recent compilation), although there is a range of proposed power-law indices, depending on selected samples and methodologies (Muzerolle et al. 2003; Barentsen et al. 2011; Rigliaco et al. 2011; Venuti et al. 2014). Similarly, a log-linear relationship has been found between the accretion rate and $H\alpha W_{10}$, with $\log \dot{M}_{\text{acc}} \propto [0.5...2] \times 10^{-2} W_{10}$ (Natta et al. 2004; Herczeg & Hillenbrand 2008; Alcalá et al. 2014). Notwithstanding the caveat that this result is often based on non-simultaneous measurements, combining those two dependences, a correlation is expected between $W_{10}$ and $\log M_*$ characterized by a slope of [100...400] km s⁻<fnref n="1" /> dex⁻<fnref n="1" />. While this derivation is fraught with possible underlying biases, the slope that we observe in the $W_{10}-M_*$ diagram is thus consistent with previously derived correlations, leaving open the question of the meaningfulness of this correlation.

Generally speaking, if three quantities are each correlated with one another, it is most likely that one of the correlations is merely a consequence of the other two, rather than being indicative of a physical causality. Here, the quantities under consideration are stellar mass, stellar accretion rate and $H\alpha W_{10}$. Arguably the most intuitive physical connection that might be expected is between stellar mass and $W_{10}$. In a schematic picture where mass accretion onto the central star occurs near the free-fall velocity, one expects lower-mass stars to have lower accretion flow velocities. In order to explore this possibility in a quantitative manner, we compute $1.5 v_{\text{ff}}$ as a reasonable proxy for the resulting line $W_{10}$. Indeed, only the very extreme tails of the line profile can correspond to velocities of $\pm v_{\text{ff}}$, and projection effects further reduce the resulting radial velocity offsets as seen from the observer's point of view. We further assume that the free-fall initiates at a distance from the star of $5 R_*$, following previous studies (Gullbring et al. 1998), and adopt the stellar radii from the evolutionary models of Siess et al. (2000). The resulting stellar mass-$W_{10}$ relationship is markedly steeper ($\beta \approx 400$ km s⁻<fnref n="1" /> dex⁻<fnref n="1" />, see Fig. 8) than the correlation we observe, suggesting that the latter stems from a different mechanism. This leads us to conclude that the stellar mass-$W_{10}$ correlation is a good candidate for being a mere consequence of other, physically grounded, correlations.

In turn, this analysis supports the idea that the stellar accretion rate is correlated with both stellar mass and $W_{10}$. While the debate about the physical interpretation of the correlation between the first two quantities is ongoing, several possibilities have been proposed (e.g. Alexander & Artmitage 2006; Gregory et al. 2006; Vorobyov & Basu 2008; Manara et al. 2016). On the other hand, the physical explanation of the correlation between accretion rate and $W_{10}$ remains elusive to the point that some authors argue that there is no such mechanism (Hartmann et al. 2016). Furthermore, the fact that this correlation is generally based on (often non-

simultaneous) single measurements of ensembles of stars invites caution in its use to estimate the accretion rate in TTS quantitatively, especially in the face of the large scatter in the observed correlation (Fang et al. 2013; Alcalá et al. 2014). Nonetheless, because of the relative ease with which $W_{10}$ can be measured, it is often used as a robust quantitative proxy for the mass accretion rate. However, the validity of this approach remains to be demonstrated.

### 5.3.2 Temporal variability of individual objects

We can take advantage of our multi-epoch monitoring campaign to shed new light on the accretion rate-$W_{10}$ correlation by considering one star at a time. In doing so, we hold fixed a number of potentially important parameters, such as evolutionary state, structure of the inner disc and viewing geometry, whose large variety is probably responsible for a significant fraction of the scatter of ensemble correlations.<fnref n="1" /> We thus focus on the temporal variability of the line measurements for each of the accreting TTS in our survey. This subsample contains 23 objects, with a median of seven observations per target. Although the relationship between line profile and accretion rate is likely to be complex, comparing various observations of the same object alleviates many of the uncertainties listed above. Specifically, if $W_{10}$ is indeed a good quantitative tracer of the accretion rate, fluctuations in $W_{10}$ would readily reveal fluctuations in $\dot{M}_{\text{acc}}$. The latter is proportional to $L_{\text{acc}}$, itself correlated with the luminosity of accretion-driven emission (but see Mendigutía et al. 2015), and thus we would expect $W_{10}$ to be correlated with $L_{H\alpha}$. While we have not measured that quantity, we note that the continuum brightness variability resulting from changes in veiling for most TTS are generally $\le 50$ per cent for non-outbursting TTS (e.g. Stauffer et al. 2016), smaller than the amplitude of the line EW fluctuations for most of the accretors in our sample. Therefore, our EW measurements are a reasonable proxy for the line luminosity. We may thus expect a positive correlation between EW and $W_{10}$, which would be partially attenuated if accretion variability induces significant, correlated veiling changes (Alencar & Batalha 2002).

A plot of every epoch for every target in an EW-$W_{10}$ diagram reveals a scatter plot with no obvious correlation. This is consistent with the lack of obvious correlation between these quantities found by Costigan et al. (2012, 2014), for instance. However, because we are interested primarily in relative changes in the line strength and widths, we proceed to subtract (divide by) the weighted mean of all $W_{10}$ (EW) from each individual measurement. The results are shown in Fig. 9, in which we also plot the individual measurements from Costigan et al. (2012). Despite the large scatter, we find a strong correlation between the normalized EW and $W_{10}$ measurements, with a probability of being uncorrelated of less than $5-6 \times 10^{-6}$ for both our data set and that of Costigan et al. (2012). Combining the two samples, the null hypothesis that the two quantities are uncorrelated has a probability of $\sim 10^{-10}$. In other words, for the vast majority of CTTS, when the $H\alpha$ line becomes stronger, it becomes broader: the line profile changes in a correlated manner with the line intensity.

The limited sample number of observations per star, coupled with the limited amplitude in both line strength and width, is such that the significance of a putative correlation (as measured by a

<footnote n="1">¹ The temporal variability of the accretion rate can account for only a fraction of the total scatter in such correlations (Venuti et al. 2014).</footnote>
whose mass is $\gtrsim 1$ M$_{\odot}$, the two samples overlap substantially in the low-mass regime. For CTTS, we found a significant correlation between $W_{10}$ and stellar mass that does not seem to be related to the variation in free-fall velocity, suggesting that both quantities are instead independently correlated with a third quantity. The stellar mass accretion rate is a plausible contender for playing such a role.

We took advantage of the time series of our H$\alpha$ measurements for accreting objects to study quantitatively the variability of the line. As in previous studies, we found that most of the variability is established on time-scales as short as 3 d. We showed that, for most accretors, the $W_{10}$ of the H$\alpha$ line is positively correlated with its EW, with a slope that is consistent from star to star. We also found a similar average and dispersion of these slopes in a sample of CTTS in Chamaeleon that have been similarly monitored. We infer from this pervasive correlation that when variation of the H$\alpha$ line leads to a stronger total luminosity, it is associated with enhanced emission in the high-velocity wings. Although we cannot conclusively prove it with our data, we argue that this is strong evidence in support of the hypothesis that the mass accretion rate on the central star is directly correlated with the H$\alpha$ $W_{10}$ and, thus, that the former can be used to estimate the latter quantitatively. The physical mechanism through which this correlation is established remains to be explained. However, the similarity in the correlation slope over two samples of CTTS suggests a common mechanism, even though line profiles are highly object-dependent.

## ACKNOWLEDGEMENTS

We thank the referee for a prompt report, which allowed us to strengthen our analysis. We are grateful to the support staff at all observatories where data presented in this study were obtained, and extend particular thanks to the Calar Alto Observatory staff, who conducted our observations in service mode, and to the daytime and night support staff at the OAN-SPM for facilitating and helping us to obtain our observations. This article is based on observations made in the Observatorios de Canarias del IAC with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Observatorio del Roque de los Muchachos, and on observations collected at the Centro As-tronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de As-trofísica de Andalucía (CSIC). We thank Calar Alto Observatory for allocation of director's discretionary time to this programme. We also used observations obtained at the Observatorio Astronómico Nacional on the Sierra San Pedro Mártir (OAN-SPM), Baja Cali-fornia, México. This work was partially supported by funds from the UC Berkeley Undergraduate Research Apprenticeship Program and by the Programa de Acceso a Grandes Instalaciones Científicas (No. 2009/00157 and 2009/00203), administered by the Instituto de Astrofísica de Canarias and El Ministerio de Educación y Ciencia, España. RJDR was funded through a studentship from the Science and Technology Facilities Council (STFC) ST/F 007124/1.

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This paper has been typeset from a *TEX/LATEX* file prepared by the author.