# Rotation in NGC 2264: a study based on CoRoT photometric observations

L. Affer, G. Micela, F. Favata, E. Flaccomio, J. Bouvier

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L. Affer, G. Micela, F. Favata, E. Flaccomio, J. Bouvier. Rotation in NGC 2264: a study based on CoRoT photometric observations. Monthly Notices of the Royal Astronomical Society, 2013, 430, pp.1433-1446. 10.1093/mnras/stt003. insu-03617342

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# Rotation in NGC 2264: a study based on CoRoT* photometric observations

L. Affer,<fnref n="1" />† G. Micela,<fnref n="1" /> F. Favata,<fnref n="2" /> E. Flaccomio<fnref n="1" /> and J. Bouvier<fnref n="3" />

Accepted 2013 January 2. Received 2012 December 20; in original form 2012 July 31

## ABSTRACT

Rotation is one of the key stellar parameters which undergo substantial evolution during the stellar lifetime, in particular during the early stages. Stellar rotational periods can be determined on the basis of the periodic modulation of starlight produced by non-uniformities on the surface of the stars, due to manifestation of stellar activity. We present the results of an extensive search for rotational periods among NGC 2264 cluster members, based on photometric monitoring using the COnvection ROtation and planetary Transits (CoRoT) satellite, with particular attention to the distribution of classical and weak-line T-Tauri stars. NGC 2264 is one of the nearest and best studied star forming region in the solar neighbourhood, with an estimated age of 3 Myr, and is the object of a recent simultaneous multiband campaign including a new CoRoT observation with the aim to assess the physical origin of the observed variability. We find that the rotational distributions of classical and weak-line T-Tauri stars are different, suggesting a difference in the rotational properties of accreting and non-accreting stars.

**Key words:** stars: pre-main-sequence – stars: rotation.

## 1 INTRODUCTION

Over the last few years, the determination of stellar rotation rates for large samples of stars with different masses and ages in young open clusters, has made substantial progress, providing a large observational sampling of the angular momentum evolution of pre-main-sequence stars (Bouvier 2008, 2009). The precise mechanisms governing angular momentum evolution of pre-main-sequence low-mass stars are still not well understood, but basically they can be schematized with two main competing processes: star contraction and star–disc interaction. Stars in the pre-main-sequence phase are still contracting; thus, increasing their angular velocity to conserve the angular momentum. On the other hand, the observed existence of slow rotators and of a wide dispersion in rotation rates of cluster stars on the zero-age main sequence (ZAMS) can be explained only with the presence of a competing mechanism of angular momentum loss (i.e. spin-down of the star), different from star to star, during the pre-main-sequence phase. It is generally believed that this mechanism can be explained by the magnetic interaction between stellar magnetospheres and circumstellar discs, in a scenario known as *disc locking*, first proposed by Camenzind (1990) and Koenigl (1991) and explained in detail by Shu et al. (1994), which assumes that

the angular momentum deposited on an accreting star (due to mass accretion from disc to star; Edwards et al. 1993) is exactly removed by torques carried along magnetic field lines connecting the star to the disc. The wide dispersion of rotational velocities observed on the ZAMS is the result of different disc lifetimes (Bouvier et al. 1993). Several observational results indicate a relation between the presence of discs and rotational evolution, in particular population of stars with discs, on average, rotate more slowly than those without discs and does exist a statistically significant anticorrelation between angular velocity and disc indicators such as near-infrared (NIR) excess and $H\alpha$ equivalent width (EW; Bouvier et al. 1993; Edwards et al. 1993; Herbst et al. 2000, 2002; Lamm et al. 2005; Rebull et al. 2006). Moreover, the disc-locking scenario predicts that the torques arising from the magnetic connection between the star and the disc remove substantial angular momentum enforcing an equilibrium angular spin rate (Choi & Herbst 1996) which is in agreement with the constant rotation period in the 2–8 d range, characteristic of the majority of young stars. However, there have been several conflicting theoretical and observational evidences concerning the role of disc-locking scenario in the evolution of low-mass pre-main-sequence stars. Dahm & Simon (2005) pointed out that the $P_{\text{rot}}$ distribution histograms for weak T-Tauri stars (WTTSs, whose periodic variability is believed to be induced by large starspots) and classical T-Tauri stars (CTTSs, whose variability may be also due to accretion spots and shadowing of the photosphere from dusty disc structures) in NGC 2264 are very similar and do not indicate that CTTSs are rotating more slowly than their WTTS counterparts.

<footnote n="1">¹Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Palermo G. s. Vaiana, Piazza del Parlamento 1, I-90134 Palermo, Italy</footnote>

<footnote n="2">²European Space Agency, 8-10 rue Mario Nikis, F-75738 Paris Cedex 15, France</footnote>

<footnote n="3">³UJF-Grenoble 1/CNRS-INSU, Institut de Planètologie et d'Astrophysique de Grenoble (IPAG) UMR 5274, F-38041 Grenoble, France</footnote>

<footnote>* The CoRoT space mission, launched on 2006 December 27, was developed and is operated by the CNES, with participation of the Science Programmes of ESA, ESA's RSSD, Austria, Belgium, Brazil, Germany and Spain.
† E-mail: affer@astropa.inaf.it</footnote>
Furthermore, Dahm & Simon (2005) did not find a correlation between $P_{\text{rot}}$ and theoretical age, as might be expected if stars were spinning up after decoupling from their discs. Stassun et al. (1999) and Cieza & Baliber (2006) did not find a correlation between accretion and rotation in Orion nebula cluster (ONC) and IC 348 low-mass stars, respectively (though they do not conclude that their results are inconsistent with disc locking). We have to note that most of the samples for which there is no clear evidence of a connection between the existence of discs and slow rotation, suffer from several biases, such as small sample size, sample biased towards small-mass or high-mass stars, the use of NIR photometry as disc indicator or the use of vsini values instead of rotation periods, which make them unsuited to perform this kind of test, on star-disc interaction outcomes. In particular, the presence of a NIR excess does not guarantee that the star is actually accreting mass from a disc. The studies of Cieza & Baliber (2007) and Rebull et al. (2005), based on *Spitzer* mid-infrared (mIR) observations, however, as well as demonstrating that objects which currently show mIR excesses are more likely accreting than not, also found differences in the rotational properties of accreting and non-accreting stars for NGC 2264 and the ONC, respectively, and represent the best test case to date, providing the strongest evidence that star-disc interaction regulates the angular momentum evolution of pre-main-sequence stars.

The idea and the basic assumptions of disc locking, sketched above, are a simplification of a much more complex phenomenon, and indeed several discussions on the shortcomings of the theory and its confrontation with observations have been put forward. In particular, Matt et al. (2010, 2012) critically examined the theory of disc locking, noting that the differential rotation between the star and disc naturally leads to an opening (i.e. disconnecting) of the magnetic field between the two. They find that this significantly reduces the spin-down torque on the star by the disc, thus, disc locking cannot account (at least, alone) for the slow rotation observed in several systems and for which the model was originally developed. Matt et al. (2010, 2012) supported the idea that stellar winds may be important during the accretion phase, they may be powered by the accretion process itself and be the key driver of angular momentum loss (Hartmann & MacGregor 1982; Paatz & Camenzind 1996; Matt & Pudritz 2005). A strong magnetically driven wind, as proposed by Matt & Pudritz (2005), is an idea which deserves further study, as well as the development of a more realistic theoretical model able to explain the full range of observed rotation periods and magnetic phenomena and the achievement of a sufficient amount of accurate data to empirically constrain them.

NGC 2264 is one of the best known star forming regions in the solar vicinity ($d \approx 760$ pc, age $\approx 3$ Myr) and is considered a benchmark for the study of star formation processes in our Galaxy. NGC 2264 luckily falls in the small portion of the sky accessible by *Convection Rotation and planetary Transits* (CoRoT; Baglin et al. 2006), and thus represents a unique chance for the mission and the study of young stars still in a formation phase. Its distance and age make it an ideal CoRoT target, its size is well suited to the CoRoT field of view, with a large fraction of cluster members falling in the appropriate magnitude range for accurate photometric monitoring in the CoRoT observations.

NGC 2264 has been extensively observed at all wavelengths from radio to X-rays (see Dahm 2008 for a review on the region), for studies of the star formation process through the observation of its outcomes: the initial mass function (e.g. Sung et al. 2008), the star formation history and the spatial structure (e.g. Teixeira et al. 2006; Sung, Stauffer & Bessell 2009). NGC 2264 is also a

primary target for the study of the evolution of the stellar angular momentum and its relation to circumstellar accretion (e.g. Lamm et al. 2005) of the evolution (and dispersal) of circumstellar discs (e.g. Alencar et al. 2010) and of the correlation between optical and X-ray variability of young stars (Flaccomio et al. 2010). Among several optical, infrared (IR) and X-ray surveys, both photometric and spectroscopic, on NGC 2264, the most recent are Sung et al. (2008), who have provided the widest area and deepest publicly available optical photometry; Sung et al. (2009), who have published *Spitzer* (IRAC + MIPS) photometry; Rebull et al. (2002) and Dahm & Simon (2005), who have published spectral types, $H\alpha$ and Li EWs, from low-dispersion spectra, for a total of $\sim 500$ members; Fűrész et al. (2006), who have published radial velocities for 436 stars.

Lamm et al. (2004) performed a photometric monitoring of about 10 600 stars to search for periodic and irregular variable pre-main-sequence stars and found 543 periodic variables with periods between 0.2 and 15 d, and 484 irregular variables. Lamm et al. (2005) used this extensive study to conclude that the period distribution in NGC 2264 is similar to that of the ONC, though shifted towards shorter periods (confirming the conclusion of Soderblom et al. 1999, based on the analysis of the rotation rates of 35 candidate members, that the stars in NGC 2264 are spun-up with respect to members of the ONC).

The period distribution found by Lamm et al. (2005) is unimodal for masses lower than $0.25 M_{\odot}$ while it is bimodal for more massive stars. Lamm et al. (2005) also found evidence for disc locking with a constant period, among 30 per cent of the higher mass stars (with a locking period of $\sim 8$ d), while disc locking is less important among lower mass stars, whose peak in the period distribution at 2–3 d suggests that these stars have undergone a low rate of angular momentum loss from star-disc interaction, while not completely locked [an evolution scenario defined by Lamm et al. (2005) as ‘moderate’ angular momentum loss].

The bimodality is interpreted as an effect of disc-star interactions in pre-main-sequence stars, slow rotators being interpreted as stars that are magnetically locked to their discs, preventing them from spinning up with time and accounting for the broad period distribution of ZAMS stars. This assumption is supported by some observational results showing that WTTSs are rotating faster than CTTSs with inner discs (Bouvier et al. 1993; Edwards et al. 1993). Nevertheless, the hypothesis that accreting stars rotate more slowly than non-accreting ones is still a matter of debate, since conflicting evidence exists (see e.g. Stassun et al. 1999; Dahm & Simon 2005; Lamm et al. 2005; Rebull et al. 2005, 2006; Cieza & Baliber 2006, 2007), as explained above.

The CoRoT satellite has allowed us to conduct a large-scale survey of photometric variability of NGC 2264. Thanks to the accurate high-cadence photometry and large field of view of CoRoT, we could study rotation and activity of about 8000 stars in a $3.4 \text{ deg}^2$ region. The entire star-forming region fits into a single CoRoT field of view, and the campaign resulted in continuous 23 d LCs for 301 known cluster members brighter than $V \approx 16$ ($M = 0.3–0.4 M_{\odot}$). The resulting optical broad-band LCs are the first accurate, highest cadence (32 or 512 s), longest duration, data set available for $\approx 3$ Myr old stars.

So far, the CoRoT NGC 2264 data have been used to study the correlation between optical and X-ray variability in young stars (Flaccomio et al. 2010); asteroseismological properties of two high-mass cluster members (Zwintz et al. 2011); and to identify and study the behaviour of NGC 2264 members that are AA Tau like (Alencar et al. 2010).
Alencar et al. (2010) demonstrated that the peculiar photometric behaviour of AA Tau, which consist in a flat maximum in the LC interrupted by deep quasi-periodical minima (due to obscuring material with a variable structure which is located in the inner disc region, near the corotation radius), that vary in depth and width from one rotational cycle to the other, is quite common among CTTSs (Bouvier et al. 1999, 2003, 2007; Ménard et al. 2003; Grosso et al. 2007). The interpretation for AA Tau can now be considered quite solid, and its extension to a high fraction of CTTSs simply requires that the size of the obscuring clump of material (e.g. the height of the inner disc warp) is larger than previously thought.

In a rather similar scenario of circumstellar material orbiting the star and consequent time-variable shading, Flaccomio et al. (2010) found evidence of a correlation between soft X-ray and optical variability of CTTSs (no correlation is apparent in the hard band), while no correlation in either band (soft and hard) is present in WTTSs. Flaccomio et al. (2010) suggested that this observation is consistent with a scenario in which a significant fraction of the X-ray and optical emission from CTTSs is affected by temporally variable shading and obscuration.

The conclusions of both Alencar et al. (2010) and Flaccomio et al. (2010) point towards a different origin of the observed periods, suggesting a difference both in the physical and morphological properties of CTTSs and WTTSs.

In this paper, we derive accurate rotational periods of known NGC 2264 members, testing whether a relationship between accretion and rotation exists in pre-main-sequence stars.

In the following, we describe the observational and data reduction strategy (Sections 2 and 3). In Section 4, we discuss the results obtained and our major conclusions are summarized in Section 5.

## 2 CoRoT OBSERVATIONS

The first short run CoRoT observation (SRa01; P.I. F Favata) lasted from 2008 March 7 to 31 (23 d) and was devoted to the observation of the very young (~3 Myr) stellar open cluster NGC 2264, which covers most of the mass sequence from ~3 to ~0.1 $M_\odot$.

A total of 8150 stars were observed, with right ascension (RA) between 99.4 and 100.9 and declination (Dec.) between 7.6 and 10.3 and *R* magnitudes from 9.2 to 16.0. The sample includes 301 cluster members (see Section 3 for details regarding membership criteria). We used the so called N2 data delivered by the CoRoT pipeline (Samadi et al. 2007) after correction of the electronic offset, gain, electromagnetic interference and outliers. The pipeline includes background subtraction and partial jitter correction. Low-quality data points, e.g. taken during the South Atlantic Anomaly crossing or due to hot pixels events, are flagged. Some of the stars have LCs in three separate but ill-defined bands (red, green and blue). In these cases, our analysis was conducted on the white-light data obtained by summing the three bands. The LCs are sampled at a rate of 512 s or oversampled at 32 s. All the LCs presented here were rebinned to 512 s. Using CoRoT photometry we are able to reveal luminosity variation, with a precision down to 0.1 mmag $h^{-1}$ (magnitude between 11 and 16), during continuous observations, allowing us to measure photometric periods also in relatively quiet stars (for comparison, the luminosity variations of the Sun range between ~0.3 and 0.07 mmag at maximum and minimum activity, respectively; Aigrain & Irwin 2004).

<figure><img src="image_3.png" /><figcaption>**Figure 1.** Spatial distribution of the CoRoT targets in the SRa01 (dots) with target stars satisfying one or more membership criteria (big dots), as described in the text.</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>**Figure 2.** The colour–magnitude diagram of the 8150 SRa01 stars observed by CoRoT (grey dots). The large black dots indicate the 301 cluster stars satisfying one or more of the membership criteria. The crosses are WTTSs and the squares are CTTSs, defined following our criterium (WTTSs for $EW_{H\alpha} \le 5$ Å and CTTSs for $EW_{H\alpha} \ge 10$ Å). The curves denote isochrones (yr) from Siess, Forestini & Dougados (1997) (transformed to the observational plane using the Kenyon & Hartmann 1995 compilation).</figcaption></figure>

## 3 SAMPLE EXTRACTION AND LIGHT-CURVE ANALYSIS

We selected 301 cluster stars (whose spatial distribution is shown in Fig. 1 as big dots) satisfying one or more of the following membership criteria (the number of objects which fulfill the various criteria is indicated near each criterium).

(i) Detection in X-rays by Chandra ACIS or XMM-Newton (Ramírez et al. 2004; Flaccomio, Micela & Sciortino 2006; Dahm et al. 2007; Flaccomio et al., in preparation) and location on the
<figure><img src="image_5.png" /><figcaption>**Figure 3.** Four examples of morphologically different LCs (rebinned to 512 s): spot-like periodic (top-left panel); AA Tau-like system (top-right panel); irregular (bottom-left panel) and non-variable 'noisy-like' (bottom-right panel). Time is in days from 2000 January 01 (JD-245 1544.5).</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>**Figure 4.** Two examples of NGC 2264 members: the four left-hand plots are for a CTTS, CoRoT ID 0223964667, while the four right-hand plots are for a weak line T-Tauri star, CoRoT ID 0223956264. For each example, the top panels show the LC and the relative LNP, with the dotted curve superimposed indicating the 1 per cent significance threshold determined by simulations (the periods indicated in the top-right of the LNP plot are the five most significant periods yielded by the Lomb-Scargle periodogram), while the bottom panels show the LC folded with the most significant period for each example, and the autocorrelation plot with the 95 per cent confidence interval (dotted horizontal lines) with the vertical lines indicating the position of the two most significant periods found with the LNP. Time in the LCs is in days from 2000 January 01 (JD-245 1544.5).</figcaption></figure>

cluster sequence in the (*I*, *R*−*I*) diagram, when *I* and *R* magnitudes are available (191).

(ii) High levels of Hα emission, indicative of accretion, according to photometric indices (Lamm et al. 2004; Sung et al. 2008) (104).

(iii) Hα with spectroscopic EW greater than 10 Å and/or indicated to be in strong emission by Fűrész et al. (2006) (86).

(iv) Classified as Class I or Class II according to Sung et al. (2009), based on *Spitzer* mIR photometry (76).

(v) Strong optical variability + high Hα emission, indicative of high chromospheric activity, according to Lamm et al. (2004) (87).

(vi) Radial velocity members according to Fűrész et al. (2006) (192).

After selecting the cluster members, we classified them as CTTSs if their Hα EW was greater than 10 Å, and WTTSs if smaller

than 5 Å. The threshold between these two classes is a function of spectral type, as suggested by Martín (1998) and deeply analysed by Barrado y Navascués & Martín (2003). The information regarding the Hα EW is available from the work of Dahm & Simon (2005) for 164 members, 86 with EW<sub>Hα</sub> ≤ 5 Å, 19 with EW<sub>Hα</sub> between 5 and 10 Å, and 59 with EW<sub>Hα</sub> ≥ 10 Å. We decided to exclude intermediate EWs (5 < EW<sub>Hα</sub> < 10 Å), though not a usual procedure when dealing with Hα, to keep the two samples of CTTSs and WTTSs well separate and thus avoid possible ambiguity in the classification. In Fig. 2, we show the *V* versus (*V*−*I*) colour–magnitude diagram for the 8150 stars in the SRa01 observations with isochrones from Siess et al. (1997) (transformed to the observational plane using the Kenyon & Hartmann 1995 compilation), together with the NGC 2264 members.

We have analysed the CoRoT LCs as in Affer et al. (2012), we refer the reader to this work for a full description of data
<table><caption>**Table 1.** Samples used according to membership criteria, Hα EWs available from Dahm & Simon (2005) and membership-IR classification (Class II and Class III) following Sung et al. (2009).</caption><thead><tr><th>Samples</th><th>Spot-like</th><th>AA Tau like</th><th>Irregular</th><th>Non-periodic</th><th>CII</th><th>CIII</th></tr></thead><tbody><tr><td>301 members<br>164/301<br>(with Hα)</td><td>189</td><td>20</td><td>45</td><td>47</td><td>42</td><td>114</td></tr><tr><td>59 CTTS<br>(EW ≥ 10 Å)</td><td>23</td><td>12</td><td>23</td><td>1</td><td>22</td><td>6</td></tr><tr><td>19 intermediate<br>(5 &lt; EW &lt; 10 Å)</td><td>12</td><td>1</td><td>5</td><td>1</td><td>7</td><td>2</td></tr><tr><td>86 WTTS<br>(EW ≤ 5 Å)</td><td>77</td><td>2</td><td>6</td><td>1</td><td>4</td><td>59</td></tr></tbody></table>

<table><caption>**Table 2.** Catalogue of periods for NGC 2264 members.</caption><thead><tr><th>CoRot ID</th><th>Period (d)<sup>a</sup></th><th>AmpVar (per cent)<sup>b</sup></th><th>R</th><th>B-V</th><th>RA (J2000.0)</th><th>Dec. (J2000.0)</th><th>Memb-IR<sup>c</sup></th><th>EW (Hα)<sup>d</sup></th><th>Mass<sup>e</sup></th></tr></thead><tbody><tr><td>0223948127</td><td>I</td><td>20.7</td><td>15.000</td><td>-0.200</td><td>99.76562</td><td>9.67337</td><td></td><td></td><td></td></tr><tr><td>0223951807</td><td>-</td><td>0.9</td><td>14.700</td><td>1.500</td><td>99.81503</td><td>9.65377</td><td></td><td></td><td></td></tr><tr><td>0223951822</td><td>-</td><td>0.5</td><td>13.800</td><td>0.690</td><td>99.81532</td><td>9.49160</td><td></td><td></td><td></td></tr><tr><td>0223952236</td><td>-</td><td>4.6</td><td>14.100</td><td>-1.020</td><td>99.82101</td><td>9.97097</td><td></td><td></td><td></td></tr><tr><td>0223953966</td><td>3.987</td><td>3.7</td><td>12.600</td><td>-0.590</td><td>99.84448</td><td>9.28458</td><td></td><td></td><td></td></tr><tr><td>0223954040</td><td>9.684</td><td>2.7</td><td>14.000</td><td>0.030</td><td>99.84557</td><td>9.60481</td><td></td><td></td><td>1.30</td></tr><tr><td>0223954556</td><td>-</td><td>0.7</td><td>13.800</td><td>0.400</td><td>99.85257</td><td>9.37606</td><td></td><td></td><td></td></tr><tr><td>0223955032</td><td>5.436</td><td>5.3</td><td>14.300</td><td>0.460</td><td>99.85937</td><td>9.68647</td><td></td><td>-1.100</td><td>0.60</td></tr><tr><td>0223955438</td><td>-</td><td>0.7</td><td>13.400</td><td>2.200</td><td>99.86499</td><td>9.38587</td><td></td><td></td><td></td></tr><tr><td>0223955517</td><td>-</td><td>0.2</td><td>12.900</td><td>0.520</td><td>99.86609</td><td>9.47768</td><td></td><td></td><td></td></tr><tr><td>0223955994</td><td>-</td><td>0.7</td><td>13.300</td><td>0.040</td><td>99.87251</td><td>9.34971</td><td></td><td></td><td></td></tr><tr><td>0223956264</td><td>2.229</td><td>6.5</td><td>14.800</td><td>0.470</td><td>99.87656</td><td>9.56053</td><td></td><td></td><td>0.80</td></tr><tr><td>0223956963</td><td>9.786 AA</td><td>15.6</td><td>14.700</td><td>-0.200</td><td>99.88675</td><td>9.07066</td><td></td><td></td><td></td></tr><tr><td>0223957004</td><td>-</td><td>2.8</td><td>14.200</td><td>0.700</td><td>99.88737</td><td>9.94127</td><td></td><td></td><td></td></tr><tr><td>0223957142</td><td>2.568</td><td>16.9</td><td>15.200</td><td>0.600</td><td>99.88912</td><td>9.86726</td><td></td><td></td><td>0.40</td></tr><tr><td>0223957322</td><td>18.05</td><td>8.1</td><td>15.300</td><td>0.850</td><td>99.89156</td><td>9.82254</td><td></td><td></td><td>0.80</td></tr><tr><td>0223957455</td><td>10.16 AA</td><td>28.0</td><td>15.200</td><td>0.500</td><td>99.89333</td><td>9.91437</td><td></td><td></td><td></td></tr><tr><td>0223957734</td><td>-</td><td>8.1</td><td>15.300</td><td>0.690</td><td>99.89726</td><td>9.54231</td><td></td><td></td><td></td></tr><tr><td>0223957908</td><td>-</td><td>0.7</td><td>13.600</td><td>0.810</td><td>99.89991</td><td>9.40729</td><td></td><td></td><td></td></tr><tr><td>0223958794</td><td>-</td><td>2.7</td><td>14.200</td><td>0.730</td><td>99.91180</td><td>9.86451</td><td></td><td></td><td>1.60</td></tr><tr><td>0223958963</td><td>0.859</td><td>9.0</td><td>15.200</td><td>0.720</td><td>99.91379</td><td>9.93336</td><td></td><td></td><td>0.60</td></tr><tr><td>0223959618</td><td>3.922 AA</td><td>55.9</td><td>14.200</td><td>0.860</td><td>99.92274</td><td>9.77229</td><td></td><td></td><td></td></tr><tr><td>0223959652</td><td>3.732</td><td>5.7</td><td>12.700</td><td>-0.170</td><td>99.92316</td><td>9.57808</td><td></td><td>-3.300</td><td>1.40</td></tr><tr><td>0223959949</td><td>-</td><td>0.6</td><td>14.800</td><td>0.770</td><td>99.92764</td><td>9.53115</td><td></td><td></td><td></td></tr><tr><td>0223960995</td><td>-</td><td>0.6</td><td>14.500</td><td>1.310</td><td>99.94267</td><td>9.80571</td><td></td><td></td><td></td></tr><tr><td>0223961132</td><td>3.839</td><td>9.3</td><td>12.500</td><td>0.210</td><td>99.94466</td><td>9.68178</td><td>III</td><td></td><td>1.40</td></tr><tr><td>0223961409</td><td>1.104</td><td>0.7</td><td>11.900</td><td>-0.030</td><td>99.94879</td><td>9.43535</td><td>III</td><td></td><td></td></tr><tr><td>0223961560</td><td>-</td><td>1.4</td><td>12.700</td><td>1.570</td><td>99.95090</td><td>9.98496</td><td></td><td></td><td></td></tr><tr><td>0223961941</td><td>6.52</td><td>4.3</td><td>14.700</td><td>0.400</td><td>99.95667</td><td>9.55630</td><td>III</td><td></td><td>1.10</td></tr><tr><td>0223962024</td><td>-</td><td>0.7</td><td>14.500</td><td>2.900</td><td>99.95769</td><td>9.93945</td><td></td><td></td><td></td></tr><tr><td>0223962712</td><td>-</td><td>1.6</td><td>14.500</td><td>0.970</td><td>99.96801</td><td>9.31938</td><td></td><td></td><td></td></tr><tr><td>0223963678</td><td>0.676</td><td>5.0</td><td>14.700</td><td>0.600</td><td>99.98199</td><td>9.79233</td><td>III</td><td></td><td></td></tr><tr><td>0223963815</td><td>-</td><td>1.5</td><td>13.200</td><td>0.100</td><td>99.98402</td><td>9.51299</td><td></td><td></td><td></td></tr><tr><td>0223963881</td><td>12.92</td><td>0.7</td><td>13.700</td><td>-0.400</td><td>99.98499</td><td>9.72557</td><td>III</td><td></td><td></td></tr><tr><td>0223963994</td><td>-</td><td>0.2</td><td>15.200</td><td>-1.200</td><td>99.98674</td><td>9.74040</td><td></td><td></td><td></td></tr><tr><td>0223964667</td><td>6.456</td><td>79.3</td><td>15.300</td><td>-0.200</td><td>99.99690</td><td>9.45691</td><td></td><td></td><td></td></tr><tr><td>0223964830</td><td>2.575</td><td>9.1</td><td>15.900</td><td>0.530</td><td>99.99934</td><td>9.56164</td><td>III</td><td></td><td>0.80</td></tr><tr><td>0223965280</td><td>-</td><td>0.7</td><td>14.500</td><td>0.970</td><td>100.00603</td><td>9.51846</td><td></td><td></td><td></td></tr><tr><td>0223965459</td><td>1.351</td><td>15.4</td><td>15.600</td><td>0.700</td><td>100.00892</td><td>9.75401</td><td>III</td><td></td><td></td></tr><tr><td>0223965593</td><td>9.830</td><td>0.8</td><td>13.400</td><td>-0.100</td><td>100.01107</td><td>9.30565</td><td>III</td><td></td><td></td></tr><tr><td>0223965989</td><td>0.819</td><td>7.3</td><td>15.300</td><td>0.760</td><td>100.01676</td><td>9.45211</td><td>III</td><td></td><td>0.60</td></tr><tr><td>0223967301</td><td>0.957</td><td>12.6</td><td>15.800</td><td>1.360</td><td>100.03550</td><td>9.73719</td><td>III</td><td>3.500</td><td>0.50</td></tr></tbody></table>
<table><caption>**Table 2** – continued</caption><thead><tr><th>CoRoT ID</th><th>Period (d)<sup>a</sup></th><th>AmpVar (per cent)<sup>b</sup></th><th>R</th><th>B-V</th><th>RA (J2000.0)</th><th>Dec. (J2000.0)</th><th>Memb-IR<sup>c</sup></th><th>EW (Hα)<sup>d</sup></th><th>Mass<sup>e</sup></th></tr></thead><tbody><tr><td>0223967602</td><td>1.236</td><td>7.0</td><td>13.300</td><td>0.470</td><td>100.04005</td><td>9.69555</td><td>III</td><td>-1.700</td><td>1.50</td></tr><tr><td>0223967803</td><td>3.841</td><td>7.7</td><td>14.300</td><td>0.600</td><td>100.04288</td><td>9.64872</td><td>III</td><td>2.000</td><td>0.70</td></tr><tr><td>0223968039</td><td>I</td><td>56.9</td><td>15.900</td><td>0.400</td><td>100.04640</td><td>9.63503</td><td></td><td>52.90</td><td>0.90</td></tr><tr><td>0223968398</td><td>2.702</td><td>11.0</td><td>15.800</td><td>1.130</td><td>100.05183</td><td>9.73986</td><td>III</td><td>3.600</td><td>0.50</td></tr><tr><td>0223968439</td><td>8.688</td><td>31.6</td><td>15.400</td><td>-0.200</td><td>100.05240</td><td>10.09474</td><td>II</td><td></td><td></td></tr><tr><td>0223968646</td><td>–</td><td>2.0</td><td>15.400</td><td>0.500</td><td>100.05598</td><td>9.32465</td><td></td><td></td><td></td></tr><tr><td>0223968688</td><td>1.117</td><td>3.9</td><td>11.500</td><td>0.080</td><td>100.05666</td><td>9.41396</td><td>III</td><td></td><td>2.20</td></tr><tr><td>0223968804</td><td>1.295</td><td>3.9</td><td>13.600</td><td>0.660</td><td>100.05841</td><td>9.34141</td><td>III</td><td></td><td>1.40</td></tr><tr><td>0223969098</td><td>I</td><td>158.2</td><td>15.800</td><td>1.300</td><td>100.06316</td><td>10.03289</td><td></td><td></td><td></td></tr><tr><td>0223969672</td><td>–</td><td>7.2</td><td>16.000</td><td>1.000</td><td>100.07179</td><td>10.22651</td><td></td><td></td><td></td></tr><tr><td>0223970440</td><td>–</td><td>3.7</td><td>14.700</td><td>0.260</td><td>100.08372</td><td>9.47472</td><td></td><td>3.200</td><td></td></tr><tr><td>0223970694</td><td>1.467</td><td>5.2</td><td>13.000</td><td>0.010</td><td>100.08755</td><td>9.60907</td><td>III</td><td>0.300</td><td>1.50</td></tr><tr><td>0223971008</td><td>7.38</td><td>9.9</td><td>15.900</td><td>1.800</td><td>100.09258</td><td>9.90811</td><td>III</td><td>2.100</td><td>0.60</td></tr><tr><td>0223971231</td><td>I</td><td>170.8</td><td>14.500</td><td>-0.340</td><td>100.09618</td><td>9.46190</td><td></td><td>49.50</td><td>1.10</td></tr><tr><td>0223971383</td><td>4.648</td><td>11.9</td><td>15.800</td><td>0.550</td><td>100.09904</td><td>9.92345</td><td>II</td><td>80.60</td><td></td></tr><tr><td>0223971866</td><td>7.015</td><td>2.7</td><td>12.600</td><td>0.360</td><td>100.10703</td><td>9.97667</td><td>III</td><td></td><td></td></tr><tr><td>0223971984</td><td>6.281</td><td>14.0</td><td>15.500</td><td>1.480</td><td>100.10938</td><td>9.63385</td><td>III</td><td>3.500</td><td>0.60</td></tr><tr><td>0223972652</td><td>I</td><td>21.4</td><td>13.000</td><td>-0.900</td><td>100.11988</td><td>9.51704</td><td></td><td>39.10</td><td></td></tr><tr><td>0223972652</td><td>–</td><td>21.4</td><td>13.000</td><td>-0.900</td><td>100.11988</td><td>9.51704</td><td></td><td>1.800</td><td>1.60</td></tr><tr><td>0223972691</td><td>7.206</td><td>12.0</td><td>15.300</td><td>1.310</td><td>100.12061</td><td>9.70490</td><td>III</td><td>1.700</td><td>0.90</td></tr><tr><td>0223972918</td><td>–</td><td>0.9</td><td>14.100</td><td>0.930</td><td>100.12383</td><td>9.99277</td><td></td><td></td><td></td></tr><tr><td>0223972960</td><td>–</td><td>2.5</td><td>15.300</td><td>2.370</td><td>100.12453</td><td>9.83637</td><td></td><td></td><td>1.60</td></tr><tr><td>0223973200</td><td>I</td><td>113.2</td><td>15.600</td><td>0.070</td><td>100.12858</td><td>9.57811</td><td></td><td>22.20</td><td>1.30</td></tr><tr><td>0223973292</td><td>1.974</td><td>17.7</td><td>14.700</td><td>0.170</td><td>100.13010</td><td>9.51878</td><td>III</td><td>1.700</td><td>0.90</td></tr><tr><td>0223973318</td><td>I</td><td>1.0</td><td>15.600</td><td>2.600</td><td>100.13048</td><td>9.69152</td><td></td><td></td><td></td></tr><tr><td>0223973692</td><td>3.456</td><td>14.6</td><td>15.700</td><td>1.760</td><td>100.13673</td><td>9.85833</td><td></td><td>2.700</td><td>0.90</td></tr><tr><td>0223974593</td><td>1.156</td><td>18.1</td><td>14.600</td><td>0.580</td><td>100.15134</td><td>9.31610</td><td>III</td><td></td><td>0.50</td></tr><tr><td>0223974689</td><td>–</td><td>1.8</td><td>14.800</td><td>1.100</td><td>100.15278</td><td>9.36818</td><td></td><td></td><td></td></tr><tr><td>0223974891</td><td>1.212</td><td>2.9</td><td>12.900</td><td>1.740</td><td>100.15620</td><td>9.91617</td><td>III</td><td></td><td>2.10</td></tr><tr><td>0223975203</td><td>9.786</td><td>1.6</td><td>15.200</td><td>0.200</td><td>100.16160</td><td>9.36077</td><td>III</td><td></td><td>0.90</td></tr><tr><td>0223975253</td><td>–</td><td>10.5</td><td>12.600</td><td>1.440</td><td>100.16248</td><td>9.60013</td><td></td><td>3.500</td><td>0.60</td></tr><tr><td>0223975844</td><td>3.332</td><td>8.9</td><td>15.200</td><td>3.130</td><td>100.17236</td><td>9.90389</td><td>II</td><td>12.20</td><td>1.50</td></tr><tr><td>0223976028</td><td>I</td><td>4.1</td><td>13.400</td><td>0.710</td><td>100.17587</td><td>9.56050</td><td></td><td>7.300</td><td>1.70</td></tr><tr><td>0223976099</td><td>14.17</td><td>5.6</td><td>15.800</td><td>0.540</td><td>100.17683</td><td>9.53921</td><td>III</td><td>0.500</td><td>1.20</td></tr><tr><td>0223976494</td><td>2.267</td><td>12.7</td><td>14.300</td><td>0.800</td><td>100.18377</td><td>9.39887</td><td>III</td><td></td><td>1.10</td></tr><tr><td>0223976672</td><td>15.00</td><td>5.2</td><td>14.100</td><td>1.540</td><td>100.18687</td><td>9.96244</td><td>III</td><td>1.600</td><td>0.90</td></tr><tr><td>0223976747</td><td>3.173 AA</td><td>96.6</td><td>14.700</td><td>0.750</td><td>100.18816</td><td>9.47915</td><td></td><td>7.200</td><td>1.50</td></tr><tr><td>0223977051</td><td>4.53</td><td>5.5</td><td>15.200</td><td>1.410</td><td>100.19336</td><td>9.99640</td><td></td><td></td><td></td></tr><tr><td>0223977092</td><td>–</td><td>0.5</td><td>14.000</td><td>2.000</td><td>100.19403</td><td>9.36149</td><td></td><td></td><td></td></tr><tr><td>0223977232</td><td>0.712</td><td>0.8</td><td>14.300</td><td>0.340</td><td>100.19633</td><td>9.30929</td><td>III</td><td></td><td></td></tr><tr><td>0223977953</td><td>4.919 AA</td><td>26.6</td><td>15.700</td><td>0.730</td><td>100.20782</td><td>9.61389</td><td>II</td><td>66.30</td><td>1.40</td></tr><tr><td>0223978227</td><td>3.779</td><td>20.7</td><td>16.000</td><td>2.890</td><td>100.21194</td><td>9.93148</td><td>III</td><td>2.300</td><td>0.80</td></tr><tr><td>0223978308</td><td>5.374 AA</td><td>5.6</td><td>15.400</td><td>3.650</td><td>100.21328</td><td>9.74633</td><td>II</td><td>3.500</td><td>1.80</td></tr><tr><td>0223978921</td><td>I</td><td>5.4</td><td>15.800</td><td>1.400</td><td>100.22346</td><td>9.55701</td><td></td><td>18.20</td><td>1.40</td></tr><tr><td>0223978947</td><td>8.5</td><td>0.2</td><td>13.600</td><td>1.340</td><td>100.22403</td><td>9.51095</td><td>III</td><td></td><td>1.80</td></tr><tr><td>0223979728</td><td>I</td><td>8.3</td><td>15.800</td><td>1.410</td><td>100.23665</td><td>9.63043</td><td></td><td>113.2</td><td>1.10</td></tr><tr><td>0223979759</td><td>3.84</td><td>0.6</td><td>15.400</td><td>3.770</td><td>100.23719</td><td>9.81144</td><td>III</td><td>3.900</td><td>1.60</td></tr><tr><td>0223979980</td><td>0.577</td><td>6.9</td><td>14.800</td><td>2.200</td><td>100.24097</td><td>9.94176</td><td>III</td><td></td><td></td></tr><tr><td>0223980019</td><td>I</td><td>0.7</td><td>14.500</td><td>-0.500</td><td>100.24154</td><td>9.30101</td><td>III</td><td></td><td></td></tr><tr><td>0223980048</td><td>12.5 AA</td><td>24.4</td><td>14.100</td><td>1.840</td><td>100.24200</td><td>9.61504</td><td>II</td><td>34.00</td><td></td></tr><tr><td>0223980233</td><td>–</td><td>14.0</td><td>13.800</td><td>1.800</td><td>100.24457</td><td>9.60384</td><td></td><td>22.20</td><td>0.30</td></tr><tr><td>0223980258</td><td>6.990</td><td>8.9</td><td>14.900</td><td>0.980</td><td>100.24509</td><td>9.65531</td><td>II</td><td>27.90</td><td>0.60</td></tr><tr><td>0223980264</td><td>3.482 AA</td><td>54.0</td><td>14.600</td><td>0.960</td><td>100.24516</td><td>9.51607</td><td>II</td><td>14.30</td><td>1.90</td></tr><tr><td>0223980412</td><td>6.39</td><td>12.1</td><td>14.800</td><td>0.760</td><td>100.24764</td><td>9.99601</td><td>II</td><td>7.400</td><td>1.10</td></tr><tr><td>0223980447</td><td>1.675</td><td>9.2</td><td>16.000</td><td>1.220</td><td>100.24816</td><td>9.58649</td><td>II</td><td>6.400</td><td>0.90</td></tr><tr><td>0223980621</td><td>3.049</td><td>8.9</td><td>13.400</td><td>1.770</td><td>100.25099</td><td>9.98056</td><td>III</td><td>-1.200</td><td>1.80</td></tr><tr><td>0223980688</td><td>I</td><td>72.6</td><td>16.000</td><td>1.310</td><td>100.25205</td><td>9.75101</td><td></td><td>15.00</td><td>1.30</td></tr><tr><td>0223980693</td><td>5.282 AA</td><td>112.0</td><td>14.900</td><td>1.240</td><td>100.25214</td><td>9.48791</td><td>II</td><td>16.60</td><td>1.50</td></tr><tr><td>0223980807</td><td>I</td><td>8.1</td><td>14.600</td><td>1.790</td><td>100.25407</td><td>9.54585</td><td></td><td>6.400</td><td></td></tr><tr><td>0223980941</td><td>3.794</td><td>85.9</td><td>15.300</td><td>1.800</td><td>100.25637</td><td>10.24905</td><td></td><td></td><td></td></tr><tr><td>0223980988</td><td>8.58</td><td>1.6</td><td>15.400</td><td>0.000</td><td>100.25703</td><td>9.35170</td><td>III</td><td></td><td></td></tr><tr><td>0223981023</td><td>7.320 AA</td><td>38.2</td><td>15.800</td><td>1.300</td><td>100.25770</td><td>9.64490</td><td></td><td>1.500</td><td>1.50</td></tr></tbody></table>
<table><caption>Table 2 – continued</caption><thead><tr><th>CoRoT ID</th><th>Period (d)<sup>a</sup></th><th>AmpVar (per cent)<sup>b</sup></th><th>R</th><th>B-V</th><th>RA (J2000.0)</th><th>Dec. (J2000.0)</th><th>Memb-IR<sup>c</sup></th><th>EW (Hα)<sup>d</sup></th><th>Mass<sup>e</sup></th></tr></thead><tbody><tr><td>0223981174</td><td>1.974</td><td>19.7</td><td>15.600</td><td>1.000</td><td>100.26061</td><td>9.58235</td><td>III</td><td>0.600</td><td>1.50</td></tr><tr><td>0223981250</td><td>7.437</td><td>32.8</td><td>14.800</td><td>-0.200</td><td>100.26187</td><td>10.12015</td><td></td><td></td><td></td></tr><tr><td>0223981285</td><td>1.152</td><td>1.0</td><td>15.300</td><td>2.300</td><td>100.26239</td><td>9.79856</td><td>III</td><td></td><td></td></tr><tr><td>0223981349</td><td>8.014</td><td>13.4</td><td>15.000</td><td>2.300</td><td>100.26363</td><td>9.96535</td><td>III</td><td>1.500</td><td>0.80</td></tr><tr><td>0223981406</td><td>2.157</td><td>9.0</td><td>13.800</td><td>1.190</td><td>100.26449</td><td>9.52188</td><td>III</td><td>-2.500</td><td>1.60</td></tr><tr><td>0223981535</td><td>4.557</td><td>15.1</td><td>15.400</td><td>2.100</td><td>100.26640</td><td>9.96940</td><td>III</td><td>4.100</td><td></td></tr><tr><td>0223981550</td><td>14.58</td><td>0.5</td><td>14.900</td><td>-2.200</td><td>100.26661</td><td>9.39267</td><td></td><td></td><td>1.20</td></tr><tr><td>0223981753</td><td>2.971</td><td>1.1</td><td>13.000</td><td>1.070</td><td>100.26965</td><td>9.60751</td><td>III</td><td></td><td>2.50</td></tr><tr><td>0223981811</td><td>I</td><td>86.4</td><td>15.900</td><td>4.140</td><td>100.27067</td><td>9.84631</td><td></td><td>36.50</td><td>1.60</td></tr><tr><td>0223982076</td><td>2.468</td><td>3.3</td><td>13.000</td><td>2.440</td><td>100.27471</td><td>9.45502</td><td>III</td><td>2.600</td><td>0.30</td></tr><tr><td>0223982136</td><td>3.018</td><td>10.7</td><td>14.700</td><td>1.280</td><td>100.27571</td><td>9.60653</td><td></td><td>10.00</td><td>1.40</td></tr><tr><td>0223982169</td><td>3.162</td><td>10.3</td><td>14.900</td><td>1.590</td><td>100.27621</td><td>9.49197</td><td>III</td><td>3.100</td><td>0.30</td></tr><tr><td>0223982299</td><td>4.671 AA</td><td>15.1</td><td>14.700</td><td>0.400</td><td>100.27850</td><td>9.03797</td><td></td><td></td><td></td></tr><tr><td>0223982375</td><td>3.320</td><td>13.6</td><td>15.400</td><td>-0.200</td><td>100.27966</td><td>9.21076</td><td>II</td><td></td><td></td></tr><tr><td>0223982407</td><td>2.582</td><td>23.6</td><td>14.600</td><td>1.310</td><td>100.28017</td><td>9.97540</td><td>III</td><td>1.400</td><td>1.10</td></tr><tr><td>0223982423</td><td>9.026</td><td>3.8</td><td>15.800</td><td>2.400</td><td>100.28040</td><td>10.22570</td><td></td><td></td><td></td></tr><tr><td>0223982535</td><td>5.052</td><td>4.7</td><td>14.700</td><td>1.310</td><td>100.28240</td><td>9.73427</td><td>III</td><td></td><td></td></tr><tr><td>0223982779</td><td>1.882</td><td>26.8</td><td>15.600</td><td>-2.000</td><td>100.28673</td><td>9.39554</td><td>III</td><td>2.400</td><td>0.60</td></tr><tr><td>0223982807</td><td>-</td><td>2.3</td><td>13.400</td><td>5.000</td><td>100.28716</td><td>10.23981</td><td>III</td><td></td><td></td></tr><tr><td>0223983310</td><td>3.589</td><td>0.9</td><td>13.800</td><td>0.510</td><td>100.29544</td><td>10.01147</td><td>III</td><td></td><td></td></tr><tr><td>0223983509</td><td>2.390</td><td>7.89</td><td>14.100</td><td>0.300</td><td>100.29829</td><td>10.04005</td><td></td><td></td><td></td></tr><tr><td>0223983925</td><td>3.704</td><td>11.29</td><td>15.500</td><td>2.000</td><td>100.30511</td><td>9.91922</td><td></td><td>3.000</td><td></td></tr><tr><td>0223984075</td><td>3.793</td><td>3.6</td><td>12.700</td><td>1.800</td><td>100.30750</td><td>9.92897</td><td>III</td><td>-2.600</td><td></td></tr><tr><td>0223984253</td><td>10.42</td><td>9.6</td><td>16.000</td><td>1.530</td><td>100.31026</td><td>9.55614</td><td>III</td><td>1.900</td><td>1.10</td></tr><tr><td>0223984520</td><td>1.469</td><td>7.2</td><td>15.200</td><td>1.590</td><td>100.31425</td><td>9.77779</td><td>III</td><td>0.200</td><td>1.70</td></tr><tr><td>0223984572</td><td>I</td><td>14.5</td><td>12.300</td><td>2.400</td><td>100.31499</td><td>9.44282</td><td>III</td><td>5.500</td><td>0.30</td></tr><tr><td>0223984572</td><td>-</td><td>14.5</td><td>12.300</td><td>2.400</td><td>100.31499</td><td>9.44282</td><td>III</td><td></td><td></td></tr><tr><td>0223984600</td><td>5.343</td><td>1.0</td><td>13.600</td><td>-0.300</td><td>100.31541</td><td>9.63857</td><td></td><td></td><td></td></tr><tr><td>0223984608</td><td>6.098</td><td>7.7</td><td>10.200</td><td>3.180</td><td>100.31551</td><td>9.43795</td><td></td><td>1.900</td><td>1.20</td></tr><tr><td>0223985009</td><td>I</td><td>83.4</td><td>15.600</td><td>2.360</td><td>100.32182</td><td>9.90918</td><td>III</td><td>58.30</td><td>0.80</td></tr><tr><td>0223985176</td><td>6.547</td><td>8.3</td><td>15.700</td><td>1.240</td><td>100.32470</td><td>9.56046</td><td>III</td><td>2.900</td><td>0.60</td></tr><tr><td>0223985261</td><td>18.08 AA</td><td>20.3</td><td>15.400</td><td>1.280</td><td>100.32613</td><td>9.56501</td><td></td><td>28.90</td><td>1.40</td></tr><tr><td>0223985611</td><td>4.94</td><td>21.5</td><td>14.900</td><td>1.270</td><td>100.33174</td><td>9.52915</td><td>III</td><td>1.500</td><td>1.10</td></tr><tr><td>0223985845</td><td>2.604</td><td>9.4</td><td>15.900</td><td>1.220</td><td>100.33559</td><td>9.75999</td><td></td><td></td><td></td></tr><tr><td>0223985987</td><td>3.308 AA</td><td>44.3</td><td>15.300</td><td>1.300</td><td>100.33751</td><td>9.56029</td><td>III</td><td>10.60</td><td>0.90</td></tr><tr><td>0223986498</td><td>3.206</td><td>6.5</td><td>14.800</td><td>1.680</td><td>100.34600</td><td>9.45753</td><td>III</td><td></td><td></td></tr><tr><td>0223986686</td><td>-</td><td>0.6</td><td>11.900</td><td>0.090</td><td>100.34904</td><td>9.56587</td><td>II</td><td></td><td></td></tr><tr><td>0223986811</td><td>7.92</td><td>2.7</td><td>15.700</td><td>1.020</td><td>100.35109</td><td>9.53181</td><td>III</td><td></td><td></td></tr><tr><td>0223986923</td><td>8.300</td><td>0.8</td><td>15.200</td><td>1.160</td><td>100.35297</td><td>9.43999</td><td></td><td></td><td></td></tr><tr><td>0223987178</td><td>9.84 AA</td><td>36.8</td><td>15.600</td><td>0.850</td><td>100.35670</td><td>9.57878</td><td>III</td><td>15.90</td><td>0.60</td></tr><tr><td>0223987553</td><td>1.544</td><td>22.3</td><td>14.300</td><td>0.480</td><td>100.36308</td><td>9.58516</td><td>III</td><td>1.100</td><td>1.50</td></tr><tr><td>0223987997</td><td>6.456</td><td>22.9</td><td>13.800</td><td>0.020</td><td>100.36986</td><td>9.64432</td><td>II</td><td></td><td></td></tr><tr><td>0223988020</td><td>-</td><td>1.0</td><td>14.200</td><td>-0.200</td><td>100.37021</td><td>10.15428</td><td>III</td><td></td><td></td></tr><tr><td>0223988099</td><td>-</td><td>2.5</td><td>13.700</td><td>0.660</td><td>100.37155</td><td>9.66014</td><td>II</td><td>-1.400</td><td>1.60</td></tr><tr><td>0223988099</td><td>3.273</td><td>2.5</td><td>13.700</td><td>0.660</td><td>100.37155</td><td>9.66014</td><td></td><td>-1.400</td><td>1.60</td></tr><tr><td>0223988742</td><td>5.025</td><td>16.7</td><td>15.300</td><td>1.270</td><td>100.38172</td><td>9.80926</td><td></td><td>5.200</td><td>1.60</td></tr><tr><td>0223988827</td><td>4.767</td><td>9.3</td><td>15.800</td><td>0.810</td><td>100.38329</td><td>10.00690</td><td>III</td><td>13.10</td><td>1.10</td></tr><tr><td>0223988965</td><td>9.5</td><td>4.5</td><td>14.200</td><td>0.640</td><td>100.38538</td><td>9.63550</td><td>III</td><td>1.300</td><td>0.90</td></tr><tr><td>0223989567</td><td>I</td><td>8.4</td><td>15.200</td><td>1.700</td><td>100.39403</td><td>9.60913</td><td>III</td><td>4.500</td><td>0.50</td></tr><tr><td>0223989989</td><td>6.547</td><td>7.2</td><td>15.900</td><td>0.800</td><td>100.40102</td><td>9.65579</td><td>III</td><td>1.600</td><td>0.80</td></tr><tr><td>02239900299</td><td>4.469</td><td>9.3</td><td>14.500</td><td>0.660</td><td>100.40536</td><td>9.75196</td><td></td><td>35.00</td><td>1.20</td></tr><tr><td>0223990764</td><td>-</td><td>0.6</td><td>15.800</td><td>3.200</td><td>100.41270</td><td>9.49399</td><td>III</td><td></td><td></td></tr><tr><td>0223990964</td><td>10.17 AA</td><td>11.5</td><td>13.600</td><td>0.340</td><td>100.41553</td><td>9.67456</td><td>II</td><td>52.50</td><td>1.60</td></tr><tr><td>0223991355</td><td>-</td><td>0.9</td><td>12.700</td><td>0.000</td><td>100.42163</td><td>9.54543</td><td></td><td></td><td></td></tr><tr><td>0223991789</td><td>3.956</td><td>11.7</td><td>14.600</td><td>0.560</td><td>100.42803</td><td>9.71584</td><td>II</td><td>0.900</td><td>0.60</td></tr><tr><td>0223991832</td><td>8.608</td><td>18.2</td><td>16.000</td><td>-0.100</td><td>100.42868</td><td>9.41913</td><td></td><td></td><td></td></tr><tr><td>0223991967</td><td>-</td><td>0.1</td><td>12.500</td><td>0.650</td><td>100.43058</td><td>9.45033</td><td>III</td><td></td><td></td></tr><tr><td>0223992383</td><td>3.380</td><td>5.1</td><td>15.200</td><td>0.310</td><td>100.43725</td><td>9.74473</td><td>II</td><td></td><td>0.80</td></tr><tr><td>0223992685</td><td>18.5</td><td>0.7</td><td>12.300</td><td>0.300</td><td>100.44153</td><td>9.39736</td><td></td><td></td><td></td></tr><tr><td>0223993084</td><td>6.456</td><td>5.3</td><td>15.400</td><td>-0.140</td><td>100.44751</td><td>9.70001</td><td>III</td><td>2.600</td><td>0.50</td></tr><tr><td>0223993180</td><td>2.411</td><td>1.4</td><td>12.900</td><td>0.430</td><td>100.44890</td><td>9.86750</td><td>III</td><td></td><td>1.80</td></tr><tr><td>0223993199</td><td>I</td><td>40.3</td><td>14.200</td><td>0.740</td><td>100.44914</td><td>9.56957</td><td>III</td><td></td><td></td></tr></tbody></table>
<table><caption>**Table 2** – continued</caption><thead><tr><th>CoRoT ID</th><th>Period (d)<sup>a</sup></th><th>AmpVar (per cent)<sup>b</sup></th><th>R</th><th>B-V</th><th>RA (J2000.0)</th><th>Dec. (J2000.0)</th><th>Memb-IR<sup>c</sup></th><th>EW (Hα)<sup>d</sup></th><th>Mass<sup>e</sup></th></tr></thead><tbody><tr><td>0223993277</td><td>1.184</td><td>3.9</td><td>13.200</td><td>0.110</td><td>100.45027</td><td>9.71222</td><td>III</td><td></td><td>1.50</td></tr><tr><td>0223993499</td><td>I</td><td>0.9</td><td>14.500</td><td>3.200</td><td>100.45351</td><td>9.72045</td><td></td><td></td><td>1.70</td></tr><tr><td>0223993840</td><td>3.250</td><td>35.8</td><td>14.500</td><td>1.050</td><td>100.45837</td><td>9.49241</td><td>III</td><td></td><td>0.90</td></tr><tr><td>0223994268</td><td>3.762</td><td>4.9</td><td>13.200</td><td>0.240</td><td>100.46436</td><td>9.89531</td><td></td><td></td><td>1.50</td></tr><tr><td>0223994721</td><td>I</td><td>37.9</td><td>14.200</td><td>0.110</td><td>100.47102</td><td>9.96762</td><td>III</td><td></td><td>0.80</td></tr><tr><td>0223994760</td><td>5.634</td><td>8.9</td><td>14.800</td><td>0.580</td><td>100.47147</td><td>9.84660</td><td>III</td><td>1.800</td><td>1.10</td></tr><tr><td>0223995167</td><td>–</td><td>0.4</td><td>13.300</td><td>2.000</td><td>100.47691</td><td>9.48783</td><td></td><td></td><td></td></tr><tr><td>0223995308</td><td>10.5 AA</td><td>53.6</td><td>15.800</td><td>-0.130</td><td>100.47881</td><td>9.71481</td><td>II</td><td></td><td>0.30</td></tr><tr><td>0223995327</td><td>–</td><td>0.8</td><td>13.200</td><td>0.230</td><td>100.47910</td><td>9.89077</td><td></td><td></td><td></td></tr><tr><td>0223997570</td><td>3.660</td><td>6.5</td><td>14.500</td><td>0.670</td><td>100.51064</td><td>9.61480</td><td></td><td></td><td></td></tr><tr><td>0223997608</td><td>–</td><td>2.7</td><td>14.700</td><td>0.260</td><td>100.51109</td><td>9.97452</td><td></td><td></td><td></td></tr><tr><td>0223998980</td><td>–</td><td>2.2</td><td>15.500</td><td>0.600</td><td>100.52973</td><td>9.89573</td><td>III</td><td></td><td></td></tr><tr><td>0223999063</td><td>–</td><td>0.3</td><td>11.700</td><td>0.410</td><td>100.53070</td><td>9.82991</td><td></td><td></td><td></td></tr><tr><td>0223999581</td><td>–</td><td>0.5</td><td>14.200</td><td>1.220</td><td>100.53790</td><td>9.98422</td><td></td><td></td><td></td></tr><tr><td>0223999591</td><td>–</td><td>1.2</td><td>15.700</td><td>0.500</td><td>100.53800</td><td>9.80151</td><td></td><td></td><td></td></tr><tr><td>0224000646</td><td>–</td><td>0.5</td><td>13.700</td><td>0.900</td><td>100.55241</td><td>9.98546</td><td></td><td></td><td></td></tr><tr><td>0224000835</td><td>–</td><td>1.3</td><td>15.700</td><td>-0.400</td><td>100.55477</td><td>9.76773</td><td></td><td></td><td></td></tr><tr><td>0224001158</td><td>I</td><td>5.8</td><td>15.700</td><td>-0.300</td><td>100.55867</td><td>9.59576</td><td></td><td></td><td></td></tr><tr><td>0224001312</td><td>–</td><td>1.0</td><td>14.200</td><td>-0.150</td><td>100.56084</td><td>9.84115</td><td></td><td></td><td></td></tr><tr><td>0224003566</td><td>–</td><td>0.5</td><td>14.700</td><td>-0.200</td><td>100.59132</td><td>9.80927</td><td></td><td></td><td></td></tr><tr><td>0224006123</td><td>10.25 AA</td><td>53.2</td><td>13.000</td><td>0.400</td><td>100.62704</td><td>9.15735</td><td></td><td></td><td></td></tr><tr><td>0400007328</td><td>2.434</td><td>23.0</td><td>13.530</td><td>2.450</td><td>100.32380</td><td>9.49061</td><td>III</td><td>2.400</td><td>0.30</td></tr><tr><td>0400007394</td><td>3.443</td><td>4.6</td><td>14.020</td><td>3.020</td><td>100.21672</td><td>9.75134</td><td></td><td>2.800</td><td>0.50</td></tr><tr><td>0400007528</td><td>9.42</td><td>14.0</td><td>14.450</td><td>1.860</td><td>100.15780</td><td>9.58167</td><td>II</td><td>23.40</td><td>0.30</td></tr><tr><td>0400007529</td><td>4.842</td><td>9.3</td><td>14.560</td><td>2.250</td><td>100.21948</td><td>9.73917</td><td>III</td><td>2.200</td><td>0.40</td></tr><tr><td>0400007538</td><td>I</td><td>23.1</td><td>14.450</td><td>0.230</td><td>100.15217</td><td>9.84601</td><td></td><td>21.10</td><td>0.40</td></tr><tr><td>0400007614</td><td>I</td><td>13.6</td><td>14.640</td><td>1.580</td><td>100.05709</td><td>9.94183</td><td></td><td>130.2</td><td>0.40</td></tr><tr><td>0400007686</td><td>I</td><td>5.1</td><td>15.150</td><td>-8.100</td><td>100.27679</td><td>9.47745</td><td></td><td>56.10</td><td>0.40</td></tr><tr><td>0400007687</td><td>11.5</td><td>5.6</td><td>15.220</td><td>1.700</td><td>100.30544</td><td>9.86512</td><td>III</td><td>2.000</td><td>0.50</td></tr><tr><td>0400007702</td><td>5.884</td><td>20.2</td><td>15.230</td><td>1.550</td><td>100.15916</td><td>9.49792</td><td>II</td><td>2.600</td><td>0.50</td></tr><tr><td>0400007709</td><td>–</td><td>10.3</td><td>14.950</td><td>1.720</td><td>100.35226</td><td>9.62654</td><td></td><td>8.900</td><td>0.30</td></tr><tr><td>0400007734</td><td>9.996</td><td>5.6</td><td>15.200</td><td>1.830</td><td>100.36250</td><td>9.50365</td><td></td><td>25.80</td><td>0.50</td></tr><tr><td>0400007743</td><td>–</td><td>0.9</td><td>15.230</td><td>1.910</td><td>100.37020</td><td>9.58169</td><td></td><td></td><td></td></tr><tr><td>0400007765</td><td>I</td><td>2.7</td><td>15.300</td><td>1.840</td><td>100.23683</td><td>9.86573</td><td></td><td>1.100</td><td>0.30</td></tr><tr><td>0400007784</td><td>9.114</td><td>6.1</td><td>15.350</td><td>1.480</td><td>100.00467</td><td>9.59265</td><td>III</td><td></td><td></td></tr><tr><td>0400007786</td><td>8.608</td><td>6.7</td><td>15.460</td><td>1.180</td><td>100.21748</td><td>9.94537</td><td></td><td>3.100</td><td>0.50</td></tr><tr><td>0400007803</td><td>9.73</td><td>12.3</td><td>14.680</td><td>1.130</td><td>100.26503</td><td>9.50806</td><td>II</td><td>20.40</td><td></td></tr><tr><td>0400007809</td><td>3.990</td><td>14.7</td><td>15.510</td><td>1.510</td><td>100.12186</td><td>9.73542</td><td></td><td>31.30</td><td>0.40</td></tr><tr><td>0400007860</td><td>2.172</td><td>1.8</td><td>15.280</td><td>0.810</td><td>100.23959</td><td>9.82246</td><td>III</td><td></td><td></td></tr><tr><td>0400007889</td><td>1.897</td><td>46.3</td><td>15.190</td><td>1.810</td><td>100.27310</td><td>9.52793</td><td></td><td>3.000</td><td>0.30</td></tr><tr><td>0400007919</td><td>4.625</td><td>15.0</td><td>15.620</td><td>1.600</td><td>100.26164</td><td>9.38756</td><td></td><td></td><td></td></tr><tr><td>0400007955</td><td>I</td><td>17.1</td><td>15.900</td><td>1.380</td><td>100.21982</td><td>9.71679</td><td></td><td>19.40</td><td>0.30</td></tr><tr><td>0400007956</td><td>1.260</td><td>3.6</td><td>15.330</td><td>1.580</td><td>100.27903</td><td>9.68180</td><td>III</td><td>2.800</td><td></td></tr><tr><td>0400007957</td><td>I</td><td>16.9</td><td>15.820</td><td>1.680</td><td>100.32107</td><td>9.54786</td><td></td><td>2.100</td><td>0.30</td></tr><tr><td>0400007959</td><td>5.738</td><td>15.5</td><td>15.600</td><td>0.970</td><td>100.27805</td><td>9.79100</td><td>II</td><td>6.200</td><td></td></tr><tr><td>0400008031</td><td>–</td><td>29.3</td><td>15.840</td><td>1.110</td><td>100.26287</td><td>9.48460</td><td></td><td>14.60</td><td></td></tr><tr><td>0400008086</td><td>5.34</td><td>3.4</td><td>15.890</td><td>1.000</td><td>100.23363</td><td>9.71502</td><td></td><td>8.000</td><td></td></tr><tr><td>0400008126</td><td>0.546</td><td>1.7</td><td>15.540</td><td>0.970</td><td>100.29521</td><td>9.88840</td><td>III</td><td>13.20</td><td></td></tr><tr><td>0500007008</td><td>–</td><td>5.3</td><td>10.350</td><td>1.180</td><td>100.15522</td><td>9.79159</td><td></td><td></td><td></td></tr><tr><td>0500007018</td><td>1.487</td><td>1.0</td><td>10.950</td><td>1.360</td><td>100.02357</td><td>9.59702</td><td>III</td><td></td><td></td></tr><tr><td>0500007021</td><td>–</td><td>0.3</td><td>10.720</td><td>1.010</td><td>100.48482</td><td>9.83499</td><td></td><td></td><td></td></tr><tr><td>0500007022</td><td>3.332</td><td>5.6</td><td>11.050</td><td>1.310</td><td>100.30433</td><td>9.45886</td><td>III</td><td></td><td>3.00</td></tr><tr><td>0500007025</td><td>0.747</td><td>7.9</td><td>11.360</td><td>1.230</td><td>100.19200</td><td>9.82149</td><td>III</td><td></td><td></td></tr><tr><td>0500007031</td><td>–</td><td>0.8</td><td>11.450</td><td>0.820</td><td>100.19658</td><td>9.48052</td><td></td><td></td><td></td></tr><tr><td>0500007038</td><td>4.132</td><td>0.8</td><td>11.880</td><td>1.060</td><td>100.15281</td><td>9.78959</td><td>III</td><td></td><td></td></tr><tr><td>0500007039</td><td>11.92</td><td>0.6</td><td>11.980</td><td>1.140</td><td>100.27870</td><td>9.38927</td><td>III</td><td>-1.500</td><td>2.20</td></tr><tr><td>0500007046</td><td>I</td><td>3.6</td><td>12.550</td><td>1.470</td><td>100.18600</td><td>9.80059</td><td></td><td>48.90</td><td></td></tr><tr><td>0500007051</td><td>10.0</td><td>1.1</td><td>11.890</td><td>0.700</td><td>100.25919</td><td>9.86443</td><td>III</td><td>-1.600</td><td>2.10</td></tr><tr><td>0500007087</td><td>14.0</td><td>2.0</td><td>12.340</td><td>0.360</td><td>100.09639</td><td>9.93886</td><td>III</td><td></td><td></td></tr><tr><td>0500007089</td><td>I</td><td>21.4</td><td>12.320</td><td>0.260</td><td>100.30362</td><td>9.43746</td><td></td><td>85.60</td><td>1.70</td></tr><tr><td>0500007115</td><td>1.995</td><td>35.5</td><td>13.420</td><td>1.050</td><td>100.30241</td><td>9.87533</td><td>II</td><td>35.30</td><td></td></tr><tr><td>0500007120</td><td>8.53</td><td>14.2</td><td>13.450</td><td>1.010</td><td>100.19793</td><td>9.82471</td><td>II</td><td>12.80</td><td>1.80</td></tr></tbody></table>
<table><caption>Table 2 – continued</caption><thead><tr><th>CoRoT ID</th><th>Period (d)<sup>a</sup></th><th>AmpVar (per cent)<sup>b</sup></th><th>R</th><th>B-V</th><th>RA (J2000.0)</th><th>Dec. (J2000.0)</th><th>Memb-IR<sup>c</sup></th><th>EW (Hα)<sup>d</sup></th><th>Mass<sup>e</sup></th></tr></thead><tbody><tr><td>0500007122</td><td>I</td><td>57.2</td><td>12.780</td><td>0.290</td><td>100.37966</td><td>9.44951</td><td></td><td>25.90</td><td></td></tr><tr><td>0500007126</td><td>-</td><td>0.6</td><td>12.550</td><td>-0.040</td><td>100.23119</td><td>9.52272</td><td></td><td></td><td></td></tr><tr><td>0500007137</td><td>2.914</td><td>7.6</td><td>12.780</td><td>0.020</td><td>100.29095</td><td>9.45339</td><td>III</td><td>3.100</td><td>1.20</td></tr><tr><td>0500007157</td><td>4.344</td><td>7.2</td><td>13.190</td><td>0.260</td><td>100.25324</td><td>9.85620</td><td>III</td><td>1.600</td><td>1.30</td></tr><tr><td>0500007176</td><td>4.024</td><td>6.9</td><td>13.400</td><td>0.330</td><td>100.26849</td><td>9.85725</td><td>III</td><td></td><td></td></tr><tr><td>0500007197</td><td>9.114</td><td>5.0</td><td>13.570</td><td>0.220</td><td>100.18063</td><td>9.84988</td><td>III</td><td>1.700</td><td>0.80</td></tr><tr><td>0500007202</td><td>-</td><td>0.3</td><td>13.650</td><td>0.260</td><td>100.20934</td><td>9.33399</td><td></td><td></td><td></td></tr><tr><td>0500007209</td><td>I</td><td>45.2</td><td>13.600</td><td>0.170</td><td>100.21081</td><td>9.91593</td><td></td><td>11.20</td><td>1.60</td></tr><tr><td>0500007217</td><td>2.582</td><td>10.4</td><td>13.520</td><td>0.000</td><td>100.27172</td><td>9.88772</td><td>III</td><td>1.500</td><td></td></tr><tr><td>0500007221</td><td>I</td><td>9.3</td><td>13.430</td><td>-0.130</td><td>100.29939</td><td>9.44207</td><td></td><td>5.400</td><td>0.70</td></tr><tr><td>0500007227</td><td>7.151</td><td>6.9</td><td>13.880</td><td>0.280</td><td>100.12758</td><td>9.76962</td><td>III</td><td>1.500</td><td>1.30</td></tr><tr><td>0500007248</td><td>7.50</td><td>2.5</td><td>13.860</td><td>0.170</td><td>100.27125</td><td>9.86238</td><td>III</td><td>1.700</td><td>1.10</td></tr><tr><td>0500007249</td><td>I</td><td>5.9</td><td>14.680</td><td>0.980</td><td>100.41155</td><td>9.53661</td><td></td><td>58.60</td><td>1.20</td></tr><tr><td>0500007252</td><td>13.88</td><td>39.8</td><td>13.730</td><td>0.000</td><td>100.16299</td><td>9.84962</td><td>II</td><td>46.50</td><td>1.50</td></tr><tr><td>0500007269</td><td>3.674</td><td>92.7</td><td>14.530</td><td>0.740</td><td>100.17435</td><td>9.86237</td><td>II</td><td>22.90</td><td>1.10</td></tr><tr><td>0500007272</td><td>3.748</td><td>14.9</td><td>13.380</td><td>-0.420</td><td>100.16840</td><td>9.84735</td><td>III</td><td>58.30</td><td>0.70</td></tr><tr><td>0500007276</td><td>4.743</td><td>7.2</td><td>13.970</td><td>0.150</td><td>100.17261</td><td>9.80267</td><td></td><td>2.400</td><td>1.10</td></tr><tr><td>0500007283</td><td>3.217</td><td>9.6</td><td>13.940</td><td>0.100</td><td>100.23215</td><td>9.85385</td><td>II</td><td>8.000</td><td>1.00</td></tr><tr><td>0500007298</td><td>15.25</td><td>4.3</td><td>14.070</td><td>0.150</td><td>100.15262</td><td>9.80638</td><td>III</td><td>4.900</td><td>1.10</td></tr><tr><td>0500007300</td><td>I</td><td>0.7</td><td>13.480</td><td>-0.450</td><td>100.15151</td><td>9.37904</td><td></td><td></td><td></td></tr><tr><td>0500007308</td><td>3.141</td><td>9.3</td><td>14.200</td><td>0.230</td><td>100.10616</td><td>9.80721</td><td>III</td><td>0.800</td><td>1.10</td></tr><tr><td>0500007315</td><td>7.812 AA</td><td>32.9</td><td>13.920</td><td>-0.080</td><td>100.17216</td><td>9.85066</td><td>II</td><td>24.50</td><td>0.80</td></tr><tr><td>0500007330</td><td>4.304</td><td>3.5</td><td>14.030</td><td>-0.030</td><td>100.27422</td><td>9.87996</td><td>III</td><td>0.900</td><td>0.80</td></tr><tr><td>0500007335</td><td>14.99 AA</td><td>8.8</td><td>14.020</td><td>-0.070</td><td>100.26789</td><td>9.41449</td><td>II</td><td>101.8</td><td>0.60</td></tr><tr><td>0500007347</td><td>4.206</td><td>15.3</td><td>14.210</td><td>0.060</td><td>100.25000</td><td>9.48057</td><td>III</td><td>1.700</td><td>0.80</td></tr><tr><td>0500007354</td><td>1.165</td><td>11.6</td><td>14.240</td><td>0.050</td><td>100.22991</td><td>9.84718</td><td></td><td>2.800</td><td>1.00</td></tr><tr><td>0500007366</td><td>3.617</td><td>8.2</td><td>14.060</td><td>-0.190</td><td>100.19733</td><td>9.81373</td><td>III</td><td>1.800</td><td>0.50</td></tr><tr><td>0500007369</td><td>I</td><td>15.2</td><td>13.590</td><td>-0.680</td><td>100.27808</td><td>9.57943</td><td></td><td>49.40</td><td></td></tr><tr><td>0500007379</td><td>14.17</td><td>2.7</td><td>14.300</td><td>-0.010</td><td>100.17095</td><td>9.79936</td><td></td><td>7.500</td><td>0.80</td></tr><tr><td>0500007383</td><td>1.289</td><td>4.8</td><td>13.970</td><td>-0.360</td><td>100.27368</td><td>9.90520</td><td>III</td><td>3.800</td><td>0.50</td></tr><tr><td>0500007410</td><td>-</td><td>2.8</td><td>14.050</td><td>-0.390</td><td>100.21897</td><td>9.86833</td><td></td><td>6.900</td><td>0.70</td></tr><tr><td>0500007416</td><td>3.748</td><td>3.5</td><td>14.170</td><td>-0.300</td><td>100.27124</td><td>9.81332</td><td>III</td><td></td><td></td></tr><tr><td>0500007457</td><td>1.049</td><td>3.0</td><td>14.480</td><td>-0.130</td><td>100.17415</td><td>9.83120</td><td>III</td><td>4.200</td><td>0.60</td></tr><tr><td>0500007458</td><td>4.625</td><td>5.8</td><td>14.490</td><td>-0.130</td><td>100.18768</td><td>9.76162</td><td></td><td>2.400</td><td>0.80</td></tr><tr><td>0500007460</td><td>8.49 AA</td><td>42.0</td><td>14.600</td><td>-0.030</td><td>100.18006</td><td>9.78535</td><td>II</td><td>27.10</td><td>0.90</td></tr><tr><td>0500007473</td><td>I</td><td>24.9</td><td>14.430</td><td>-0.260</td><td>100.22610</td><td>9.82232</td><td></td><td>161.1</td><td>0.50</td></tr><tr><td>0500007505</td><td>I</td><td>8.3</td><td>14.900</td><td>0.070</td><td>100.17086</td><td>9.46509</td><td></td><td>13.20</td><td></td></tr><tr><td>0500007550</td><td>-</td><td>0.4</td><td>14.590</td><td>-0.440</td><td>100.40549</td><td>9.53271</td><td></td><td></td><td></td></tr><tr><td>0500007556</td><td>3.405</td><td>4.5</td><td>14.250</td><td>-0.810</td><td>100.34229</td><td>9.35863</td><td>III</td><td>3.800</td><td></td></tr><tr><td>0500007572</td><td>8.08</td><td>3.2</td><td>14.440</td><td>-0.670</td><td>100.29298</td><td>9.36376</td><td>III</td><td>2.700</td><td></td></tr><tr><td>0500007580</td><td>1.805</td><td>17.5</td><td>14.700</td><td>-0.450</td><td>100.24931</td><td>9.86359</td><td>III</td><td>4.900</td><td>0.40</td></tr><tr><td>0500007585</td><td>9.786</td><td>14.3</td><td>14.780</td><td>-0.410</td><td>100.19170</td><td>9.29951</td><td></td><td></td><td></td></tr><tr><td>0500007610</td><td>9.34</td><td>17.4</td><td>14.690</td><td>-0.610</td><td>100.24792</td><td>9.49770</td><td>II</td><td>26.20</td><td>0.30</td></tr><tr><td>0500007634</td><td>11.25</td><td>6.7</td><td>14.970</td><td>-0.410</td><td>100.26488</td><td>10.00983</td><td></td><td>6.900</td><td>0.50</td></tr><tr><td>0500007667</td><td>5.405</td><td>22.6</td><td>15.190</td><td>-0.340</td><td>100.31035</td><td>9.62065</td><td>III</td><td>4.100</td><td></td></tr><tr><td>0500007682</td><td>I</td><td>7.9</td><td>14.580</td><td>-1.010</td><td>100.31008</td><td>9.44952</td><td></td><td>2.700</td><td>0.30</td></tr><tr><td>0500007708</td><td>9.584</td><td>11.4</td><td>15.220</td><td>-0.450</td><td>100.22546</td><td>9.49752</td><td>III</td><td>3.600</td><td></td></tr><tr><td>0500007727</td><td>I</td><td>20.7</td><td>15.150</td><td>-0.590</td><td>100.29583</td><td>9.59881</td><td></td><td>61.50</td><td>0.80</td></tr><tr><td>0500007730</td><td>12.5</td><td>3.2</td><td>14.850</td><td>-0.910</td><td>100.20505</td><td>9.96077</td><td></td><td>50.80</td><td>0.50</td></tr><tr><td>0500007752</td><td>4.042</td><td>5.4</td><td>14.720</td><td>-1.110</td><td>100.28734</td><td>9.56278</td><td>II</td><td>51.00</td><td>0.30</td></tr><tr><td>0500007766</td><td>I</td><td>7.2</td><td>15.070</td><td>-0.800</td><td>100.29283</td><td>9.55696</td><td></td><td>2.700</td><td>0.30</td></tr><tr><td>0500007770</td><td>10.0</td><td>4.4</td><td>15.300</td><td>-0.580</td><td>100.01115</td><td>9.69690</td><td>III</td><td></td><td></td></tr><tr><td>0500007794</td><td>8.854</td><td>7.1</td><td>15.410</td><td>-0.530</td><td>100.23939</td><td>9.48984</td><td>III</td><td>4.000</td><td></td></tr><tr><td>0500007808</td><td>5.025</td><td>2.9</td><td>15.060</td><td>-0.920</td><td>100.29496</td><td>9.77811</td><td>III</td><td>3.900</td><td>0.30</td></tr><tr><td>0500007816</td><td>7.378</td><td>1.1</td><td>15.060</td><td>-0.980</td><td>100.22344</td><td>9.78455</td><td>II</td><td>8.100</td><td>0.30</td></tr><tr><td>0500007837</td><td>I</td><td>19.5</td><td>15.380</td><td>-0.740</td><td>100.28690</td><td>9.88365</td><td></td><td></td><td></td></tr><tr><td>0500007857</td><td>I</td><td>8.0</td><td>15.360</td><td>-0.820</td><td>100.26905</td><td>9.64190</td><td></td><td>108.0</td><td>0.30</td></tr><tr><td>0500007874</td><td>I</td><td>3.3</td><td>15.740</td><td>-0.500</td><td>100.18720</td><td>9.81921</td><td></td><td>2.600</td><td></td></tr><tr><td>0500007896</td><td>9.296</td><td>14.0</td><td>14.950</td><td>-1.360</td><td>100.27596</td><td>9.41769</td><td>II</td><td>34.70</td><td>0.20</td></tr><tr><td>0500007918</td><td>I</td><td>2.7</td><td>15.330</td><td>-1.070</td><td>100.14539</td><td>9.90200</td><td></td><td>5.200</td><td>0.30</td></tr><tr><td>0500007930</td><td>6.30</td><td>19.8</td><td>15.620</td><td>-0.810</td><td>100.18580</td><td>9.54061</td><td></td><td>60.00</td><td>0.30</td></tr><tr><td>0500007939</td><td>1.029</td><td>5.3</td><td>15.430</td><td>1.200</td><td>100.24333</td><td>9.45696</td><td>III</td><td>6.700</td><td></td></tr></tbody></table>
<table><caption>**Table 2** – continued</caption><thead><tr><th>CoRoT ID</th><th>Period (d)<sup>a</sup></th><th>AmpVar (per cent)<sup>b</sup></th><th>R</th><th>B-V</th><th>RA (J2000.0)</th><th>Dec. (J2000.0)</th><th>Memb-IR<sup>c</sup></th><th>EW (Hα)<sup>d</sup></th><th>Mass<sup>e</sup></th></tr></thead><tbody><tr><td>0500007963</td><td>2.568</td><td>28.6</td><td>15.880</td><td>-0.660</td><td>100.19968</td><td>9.55087</td><td></td><td></td><td></td></tr><tr><td>0500007992</td><td>2.318</td><td>2.4</td><td>15.170</td><td>-1.480</td><td>100.19115</td><td>9.64566</td><td>III</td><td>4.100</td><td></td></tr><tr><td>0500008003</td><td>3.19</td><td>5.0</td><td>15.630</td><td>-1.070</td><td>100.35450</td><td>9.60005</td><td>III</td><td></td><td></td></tr><tr><td>0500008007</td><td>1.805</td><td>4.4</td><td>15.900</td><td>-0.820</td><td>100.17437</td><td>9.69406</td><td></td><td>3.100</td><td></td></tr><tr><td>0500008038</td><td>3.469</td><td>6.7</td><td>15.660</td><td>-1.150</td><td>100.10687</td><td>9.99993</td><td>II</td><td></td><td>0.30</td></tr><tr><td>0500008049</td><td>10.44</td><td>26.4</td><td>15.430</td><td>-1.420</td><td>100.32468</td><td>9.48364</td><td>II</td><td>231.4</td><td>0.40</td></tr><tr><td>0500008061</td><td>–</td><td>6.8</td><td>15.650</td><td>-1.230</td><td>100.32534</td><td>9.64038</td><td></td><td>32.50</td><td>0.30</td></tr><tr><td>0500008064</td><td>I</td><td>0.8</td><td>15.930</td><td>-0.970</td><td>100.22479</td><td>9.84946</td><td></td><td></td><td></td></tr><tr><td>0500008145</td><td>4.448</td><td>5.2</td><td>15.620</td><td>-1.590</td><td>100.16884</td><td>9.58365</td><td>II</td><td></td><td></td></tr><tr><td>0500008156</td><td>–</td><td>20.7</td><td>15.880</td><td>-1.360</td><td>100.30215</td><td>9.58578</td><td></td><td></td><td></td></tr><tr><td>0500008183</td><td>7.67</td><td>3.5</td><td>15.740</td><td>-1.610</td><td>100.27488</td><td>9.65395</td><td>II</td><td>7.400</td><td>0.20</td></tr><tr><td>0500008192</td><td>2.408</td><td>12.1</td><td>15.760</td><td>-1.620</td><td>100.30569</td><td>9.63716</td><td>II</td><td></td><td></td></tr><tr><td>0500008211</td><td>2.324</td><td>3.6</td><td>15.770</td><td>-1.700</td><td>100.26266</td><td>9.62660</td><td>II</td><td>34.10</td><td>0.50</td></tr><tr><td>0500008213</td><td>4.364</td><td>3.9</td><td>15.880</td><td>-1.600</td><td>100.27111</td><td>9.82302</td><td>II</td><td>8.300</td><td></td></tr></tbody></table>

<sup>a</sup>I indicates irregular variables, AA indicates AA Tau-type stars.

<sup>b</sup>Short term variability amplitude of the LCs.

<sup>c</sup>Membership-IR classification (Class II and Class III) of Sung et al. (2009), considering also other membership criteria listed in Sung et al. (2008).

<sup>d</sup>Hα EW from Lamm et al. (2004).

<sup>e</sup>Masses are from the Siess et al. (2000) tracks. Stars were placed in the T<sub>eff</sub>, L<sub>bol</sub> diagram converting spectral types to T<sub>eff</sub> and I band and (in absence of the I magnitude) V-band bolometric corrections, using Kenyon & Hartmann (1996).

reduction and analysis. In brief, we prepared the LCs by correcting the following systematic effects: spurious data points (mainly due to cosmic rays and/or to the satellite crossing of the South Atlantic anomaly), as flagged by the reduction pipeline were removed; we rebinned the data to 2 h to smooth out the orbital period of the satellite (1.7 h); spurious long period trends (due to pointing and instrumental drift) were removed by fitting a third degree polynomial to the data and then dividing the original data points by this function.

The presence of periodic signals was detected using the Lomb Normalized Periodogram (LNP) technique (Scargle 1982; Horne & Baliunas 1986). With this algorithm we calculated the normalized power P(ω) as function of angular frequency ω = 2πν and identified the location of the highest peak in the periodogram. In order to decide the significance of the peak we have followed Eaton, Herbst & Hillenbrand (1995), randomizing the temporal bins from the original LC. By calculating the maximum power on a large number of randomized data sets, the conversion from power to False Alarm Probability (FAP) can be determined. In detail, we constructed 1000 LCs resampled from the original ones randomizing the position of blocks of adjacent temporal bins (block length, 12 h; e.g. Flaccomio et al. 2005). By shuffling the data we break any possible time correlation and periodicity of the LC on time-scales longer than the block duration. We calculated the Scargle periodogram for all the randomized LCs and we compared the maximum from the real periodogram to the distribution obtained from the randomized LCs, at the same frequency, in order to establish the probability that values as high as the observed one are due to random fluctuations. Given some threshold FAP<sub>*</sub> we state that the detected candidate periodicity is statistically not significant if FAP > FAP<sub>*</sub>. The calculation we performed on CoRoT LCs led often to small FAPs, indicating that LNPs of our LCs present peaks that in most cases cannot be explained by pure stochastic noise, or non-periodic variability on time-scales shorter than 12 h. In fact, if LCs present variations on time-scale smaller than the size of the temporal block we used in the simulations, these variations will be still present in the simulated curves and will be not recognized as significant (more details in Affer et al. 2012). We have chosen a bin size of 12 h as a reasonable compromise between the expected time-scale

of stochastic variations and the shortest expected periodic signal. Once significant peaks (at FAP 1 per cent; since we simulated 1000 LCs, the 1 per cent FAP power is the power that was exceeded by the highest peak in 10 simulations) were determined from the LNPs, we also used an autocorrelation analysis (Box & Jenkins 1976) to validate the periodicity of the LCs and to eliminate or correct spurious periods due to aliasing effects (in 5 per cent of the cases, with a 95 per cent confidence interval) or residual effects due to the choice of temporal blocks used in the LCs' simulations (block length, 12 h).

Autocorrelation takes each point of the LC measured at time t and compares the value of that point to another at time t + L. Points separated by L will have very similar values if the data contained some variability with period L; thus, the autocorrelation function will have peaks corresponding to periods of variability in the data. The autocorrelation r<sub>L</sub> of a sample population X as a function of the lag L is

$$r_L = \frac{\sum_{k=0}^{N-L-1} (x_k - \bar{x})(x_{k+L} - \bar{x})}{\sum_{k=0}^{N-1} (x_k - \bar{x})^2},$$

where x̄ is the mean of the sample population X and N is the sample size, the quantity r<sub>L</sub> is called the autocorrelation coefficient at lag L. The correlogram for a time series is a plot of the autocorrelation coefficients r<sub>L</sub> as a function of L. A time series is random if it consists of a series of independent observations with the same distribution. In this case, we would expect r<sub>L</sub> to be statistically not significant for all values of L. We have chosen to adopt a 95 per cent confidence level to select significant autocorrelation coefficient.

Following Alencar et al. (2010), morphologically we can divide the LCs in four groups: (1) spot-like periodic LCs, whose periodicity can be interpreted as rotational modulation of surface features such as cool and/or hotspots (Fig. 3, top-left panel); (2) AA Tau-like systems, whose quasi-periodicity is likely caused by the obscuration of the stellar photosphere by circumstellar disc material (Fig. 3, top-right panel), the stability of the spot-like LCs on the time-scale of the observations, makes them easily distinguishable from the AA Tau-like ones; (3) irregular LCs, whose non-periodic brightness modulations (some of them with peak-to-peak variations up to 1 mag) are probably due to a complex mixing of non-steady
<figure><img src="image_7.png" /><figcaption>**Figure 5.** Left-hand panel: rotational period distribution for NGC 2264 members, the inset plot is the same diagram but zoomed into the period region between 0 and 6 d. Right-hand panel: rotational period distributions for CTTSs (solid line) and for WTTSs (dashed line).</figcaption></figure>

<figure><img src="image_8.png" /></figure>

accretion phenomena, and obscuration by non-uniformly distributed circumstellar material, as suggested by Alencar et al. (2010) (Fig. 3, bottom-left panel); and (4) non-variable LCs which do not display an obvious periodicity, most of which look like noisy LCs with small variability amplitude ≤1 per cent (Fig. 3, bottom-right panel).

To evaluate a short term variability amplitude of the LC, we calculated the running median flux, obtained using a temporal bin set up by 15 time points (thus, a time-scale of 15 × 512 s), we calculated for each time value the difference between the instantaneous flux and the running median flux derived at the corresponding time, obtaining an array. We measured the amplitude variation of the LC as the difference between the maximum and the minimum values of this array. We found that the variability amplitude range is 2 to 171 per cent for CTTSs and 1.0 to 38 per cent for WTTSs in our sample. In Fig. 4, we show the results of the complete analysis for two LCs, one belonging to a CTTS and the other to a WTTS.

<figure><img src="image_9.png" /><figcaption>**Figure 6.** Rotational period distribution for Class II (dashed line) and Class III members (solid line). The two classes were selected following the membership-IR classification of Sung et al. (2009) and other membership listed in Sung et al. (2008).</figcaption></figure>

## 4 RESULTS: ROTATIONAL PERIODS

Of the 301 monitored cluster members, we found that 189 are periodic variables, with regular LCs, possibly resulting from the rotational modulation of the light by stellar spots, 20 are AA Tau-like systems, 45 are irregular LCs and 47 display no significant variability (noise dominated LCs). Among the 86 WTTSs, we measured periods for 76 stars (74 regular and 2 AA Tau like), 6 were found to be irregular and 1 non-variable. For 3 stars we did measure a period, the variability is clearly due to spot, nonetheless we discarded these periods as they are not significant according to both the LNP and autocorrelation methods. Among the 59 CTTSs, we measured periods for 33 stars (21 regular and 12 AA Tau like), 23 were found to be irregular and 1 non-variable, for two stars the periods found were discarded as not significant. In Table 1, we list the samples used in this work, indicating the morphological division performed (spot like, AA Tau like, etc.) and the membership-IR classification (Class II and Class III) following Sung et al. (2009).

All the rotational periods derived for NGC 2264 members are reported in Table 2. For each star we list: the CoRoT ID; the derived period; the variability amplitude AmpVar; the R magnitude; the B-V magnitude; the RA and Dec.; the membership-IR classification (Class II and Class III) following Sung et al. (2009) and other membership criteria listed in Sung et al. (2008); the Hα EWs from Dahm & Simon (2005) and the mass from the Siess, Dufour & Forestini (2000) tracks.

In the left-hand panel of Fig. 5, we show the rotational period distribution for NGC 2264 members, while the distribution of rotational periods for CTTSs and WTTSs is shown in the right-hand

panel. Although the statistics are limited, it is evident that the period distribution of the CTTSs looks quite different from that of the WTTSs, with CTTSs being slower rotators on average (median $P_{Rot} = 7.0$ d) with respect to WTTSs (median $P_{Rot} = 4.2$ d), in the cluster NGC 2264. According to a Kolmogorov-Smirnov (KS) test (Press et al. 2002), there is only a probability of 2 per cent that the two distributions are equivalent.

The peaks of the distribution for CTTSs are located at about $P = 3–5$ and 9 d. WTTSs distribution suggests two peaks at $P = 3–5$ and $1–2$ d. The difference is even more evident if we compare the period distributions of Class II and Class III stars, as is shown in Fig. 6. We selected Class II and Class III members following the membership-IR classification of Sung et al. (2009), using the four Spitzer IRAC bands and other membership criteria listed in Sung et al. (2008). For Class II-Class III members the KS test yields a probability of 0.2 per cent that the two distributions are drawn from the same parent population. The observed rotational period distributions are in agreement with the conclusion derived by the ground-based study of Lamm et al. (2005), on the accretion-rotation relationship, that is, differences do exist in the rotational behaviour of accreting and non-accreting stars.

Fig. 7 shows rotation period plotted as a function of stellar mass, derived from the Siess et al. (2000) tracks. The diagram shows no clear trend of rotation period with stellar mass. We calculated the period distributions in three mass intervals: $M < 0.75$ ('low'); $0.75 < M < 1.55$ ('mid'); $1.55 < M < 3.0 M_{\odot}$ ('high'). Using a KS
<figure><img src="image_10.png" /><figcaption>**Figure 7.** Rotation period as a function of stellar mass for our sample. The mass values are derived from the Siess et al. (2000) tracks.</figcaption></figure>

test, we have verified that the probabilities that the ‘low’ and ‘mid’, the ‘low’ and ‘high’, and the ‘mid’ and ‘high’ distributions are equivalent are 91 per cent, 58 per cent and 54 per cent, respectively, neither of which can lead us to infer that they are significantly different. The median periods are 4.8, 4.5 and 3.5 d for the ‘low’, ‘mid’ and ‘high’ samples, respectively.

We now compare the periods derived from the *CoRoT* data with those of Lamm et al. (2004, 2005), who identified 405 periodic variables and 184 irregular variable members. We analysed the 103 NGC 2264 members in common with the Lamm et al. (2004) ones. The *CoRoT* periods derived in this study and ground-derived ones (Lamm et al. 2004), apart from the presence of few aliases, are comparable with the exception of the 1 d periods derived from ground, likely affected by the day-night alternance (*CoRoT* LCs have both a better sampling and time coverage than Lamm et al. 2004 ones). A scatter plot of the *CoRoT* versus ground periods is shown in Fig. 8. We followed the indications of Lamm et al. (2004) to estimate the error in the measured periods, which is related to the finite frequency resolution $\delta\nu$ of the power spectrum. In our study, we take advantage of the uniformity of *CoRoT* sampling; thus, the frequency resolution is related to the total time span T of the observations (23 d) with $\delta\nu \approx 1/T$ (Roberts, Lehar & Dreher 1987). Thus, we assume as typical error in the period, that is given by $\delta P \approx (\delta\nu P^2)/2$. We found that for period shorter than 10 d, the estimated error is $\le 20$ per cent, while it grows with period. With these indications, we find that 83 per cent (85/103) of the sample stars have consistent periods in the two survey, most of the inconsistent values lie along either harmonics (9/103) or the 1 d aliases curve (5/103).

We compare ground and *CoRoT* data for few intriguing cases, in Fig. 9 we reported a LC of a star with short period illustrating the quality of the *CoRoT* LC with respect to the ground one. In Fig. 10, we show the folded LC from Lamm et al. (2004) together with the *CoRoT* one, for a case in which the ground determination of 0.84 d is clearly wrong, in comparison with the *CoRoT* determination of 5.5 d. This comparison highlights the usefulness of a continuous temporal coverage, as can only be achieved from space.

<figure><img src="image_11.png" /><figcaption>**Figure 8.** Comparison between the periods derived in this study and the ones derived by Lamm et al. (2004) for the sample stars in common. Stars with the same period in the two studies are located on the bisector (dotted line). The two dashed lines on each side of the bisector represent harmonics (0.5–2.0 P). The solid curves show the loci of the 1 $d^{-1}$ aliases.</figcaption></figure>

# 5 SUMMARY AND CONCLUSIONS

We performed an accurate study of rotation periods in the young open cluster NGC 2264, based on the very accurate *CoRoT* photometry, also to search for a correlation between accretion and stellar rotation. We derived rotational period for 209 cluster members, out of 301, which are found to be periodic variables, with a spot-like modulation of their light or AA Tau like.

This work enabled us to study the distribution of rotational periods of CTTSs and WTTSs. In order to overcome the bias introduced by the use of NIR excess to classify CTTSs, we used $H\alpha$ EWs. Furthermore, the clean and continuous LCs of *CoRoT* allowed us to avoid problems due to discontinuous time sampling. Thanks to the high quality of the *CoRoT* LCs, our results provide the most complete set of rotational periods of NGC 2264 members, to date, compared to ground-based data.

As discussed in Section 1, several models assume that accreting stars may be locked to their discs by strong magnetic fields that channel streams accretion (Shu et al. 1994; Hartmann 2002). This would result in slower rotation velocities for CTTS, compared to WTTS which have no inner discs, and some observations suggested differences up to a factor of 2 in rotational velocities of CTTS versus WTTS in Taurus (Edwards et al. 1993). However, several other studies have found no significant variations between rotational velocities of CTTS and WTTS in ONC and IC 348 (Stassun et al. 1999; Rhode, Herbst & Mathieu 2001; Cieza & Baliber 2006). These results seem to suffer from several biases affecting the selected samples and even the disc and accretion indicators adopted. These differences may also be due to a classification problem, on what one defines classical and weak line T-Tauri stars.

We found that the rotational distributions of CTTSs and WTTSs are different, with WTTSs rotating faster, with a median $P_{Rot} =$
<figure><img src="image_12.png" /></figure>

**Figure 9.** LC obtained from ground observations (Lamm et al. 2004, upper-left panel, between 2000 December 30 and 2001 March 01) and the folded LC (upper-right panel). *CoRot* LC for the same star (lower-left panel) and folded LC (lower-right panel). The derived periods are indicated on the top of each folded LC panel, and are in agreement. Time in the *CoRot* LC (bottom-left panel) is in days from 2000 January 01 (JD-245 1544.5).

<figure><img src="image_13.png" /></figure>

**Figure 10.** Folded LC from Lamm et al. (2004) (top panel) with the CoRot LC and folded LC (bottom panel). In this case, the ground determination of 0.84 d is clearly wrong, compared with the CoRot determination of 5.5 d. Time in the CoRot LC (bottom-left panel) is in days from 2000 January 01 (JD-245 1544.5).

4.2 d, with respect to CTTSs, with a median $P_{\text{Rot}} = 7.0$ d. Our results are even more significant using a Class II–Class III comparison, probably because of the better statistics. This could suggest that the presence of accretion, or any other properties related to star–disc interaction, affects the rotational period. It is consistent with the disc-locking scenario (Shu et al. 1994; Hartmann 2002) and agrees with previous results in ONC (Choi & Herbst 1996; Herbst et al. 2002; Rebull et al. 2005), also confirming the previous conclusions of Lamm et al. (2005) and Cieza & Baliber (2007) for NGC 2264.

A new extensive multiband campaign has been executed on NGC 2264 in 2011 December (*CoRot+Spitzer+Chandra* complemented with *MOST* observations). The new data will enable us to tackle some open questions, on the subject of this paper, such as the stability of the disc structure responsible for the AA Tau-like variability or differential rotation and the possibility of detecting period changes, when spots evolve and appear at different latitudes.

## ACKNOWLEDGMENTS

LA and GM acknowledge support from the ASI-INAF agreement I/044/10/0. We wish to thank the anonymous referee for his/her careful reading of the manuscript and for the suggestions to improve the paper.

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