The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 Marchhttps://doi.org/10.3847/1538-4365/aaa89c© 2018. The American Astronomical Society. All rights reserved.

The 7-year MAXI/GSC Source Catalog of the Low-Galactic-latitude Sky (3MAXI)
T. Hori1 , M. Shidatsu2, Y. Ueda1 , T. Kawamuro3 , M. Morii4, S. Nakahira2, N. Isobe5, N. Kawai6 , T. Mihara2,
M. Matsuoka2, T. Morita1, M. Nakajima7, H. Negoro8, S. Oda1, T. Sakamoto9, M. Serino9, M. Sugizaki2, A. Tanimoto1 ,H. Tomida10, Y. Tsuboi11, H. Tsunemi12, S. Ueno10, K. Yamaoka13, S. Yamada1, A. Yoshida14, W. Iwakiri2, Y. Kawakubo9,
Y. Sugawara15 , S. Sugita6, Y. Tachibana6, and T. Yoshii6
1

Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan; hori@kusastro.kyoto-u.ac.jp
2
MAXI team, RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan
3
National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan
4
The Institute of Statistical Mathematics, 10-3 Midori-cho, Tachikawa, Tokyo 190-8562, Japan
5
School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan
6
Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
7
School of Dentistry at Matsudo, Nihon University, 2-870-1, Sakaecho-nishi, Matsudo, 271-8587, Chiba, Japan
8
Department of Physics, Nihon University, 1-8 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308, Japan
9
College of Science and Engineering, Department of Physics and Mathematics, Aoyama Gakuin University,
5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan10
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210, Japan
11
Department of Physics, Faculty of Science & Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo, Tokyo 112-8551, Japan
12
Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
13
Institute for Space-Earth Environmental Research (ISEE), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan
14
College of Science and Engineering, Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo, Sagamihara, Kanagawa 2525258, Japan
15
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 252-5210, Japan
Received 2017 October 4; revised 2018 January 9; accepted 2018 January 10; published 2018 February 26

Abstract
We present the ﬁrst MAXI/GSC X-ray source catalog in the low-Galactic-latitude sky ∣b∣ < 10 outside the
Galactic center region (∣b∣ < 5, l<30°, and l>330°) based on 7-year data from 2009 August 13 to 2016 July
31. To overcome source confusion in crowded regions, we have accurately calibrated the position-dependent shapeof the point-spread function of the MAXI/GSC by analyzing onboard data. We have also taken into account the
Galactic ridge X-ray emission. Using a maximum likelihood image ﬁtting method, we have detected 221 sources
with a signiﬁcance threshold >6.5σ, 7 of which are transients only detected in 73-day time-sliced images. The
faintest source has a ﬂux of 5.2×10−12 erg cm−2s−1 (or an intensity of 0.43 mCrab) in the 4–10 keV band. We
have identiﬁed the counterparts for about 81% of the detected sources, by cross-matching with the Swift, Uhuru,
RXTE, XMM-Newton, MCXC, and ROSAT all-sky survey catalogs. Our catalog contains the source name, position
and its error, ﬂux and detection signiﬁcance in the 3–4keV, 4–10keV, and 10–20keV bands, hardness ratios, andinformation on the likely counterpart for the individual detected sources. We have obtained 73-day bin light curvesof all the cataloged sources over 7 years and have calculated their periodograms. On the basis of the mean
properties of time variability and spectral hardness, we suggest that the majority of the unidentiﬁed sources are
low-mass X-ray binaries or blazars. Finally, we present the log N–log S relations at different Galactic longitudes
and for different source populations.
Key words: catalogs – surveys – X-rays: binaries
et al. 2013). While these observations achieve high sensitivities, they cover limited regions around the Galactic center or atvery low Galactic latitudes. Wider area surveys that completely
cover the low-Galactic-latitude region are necessary to provide
a complete picture of Galactic X-ray populations.
The Monitor of All-sky X-ray Image (MAXI; Matsuoka
et al. 2009) is an all-sky X-ray monitor on board the International
Space Station (ISS), and has been operating for more than 8 years
since 2009 August. Its main instrument, the Gas Slit Camera(GSC; Mihara et al. 2011), covers the energy band of 2–30 keV
and scans nearly the entire sky every 92 minutes, with an instantﬁeld of view of 3°. 0×160°. The GSC is composed of 12 onedimensional gas counters (GSC0 to GSC9, GSCA, and GSCB)
with slat collimators attached on the individual counters. Of the 12
units, 6 are placed in front of MAXI, and the others are on top ofit, producing wide rectangular ﬁelds of view in the horizontal andzenithal directions (see Mihara et al. 2011, for more detailed
information). The exposure time of a point source is ∼40–140 s

1. Introduction
Demographic studies of Galactic X-ray sources provide
important clues for understanding the evolutionary history of
our Galaxy. Many X-ray emitters over the sky, such as X-ray
binaries, supernova remnants, and cataclysmic variables, form
classes of objects at their last evolutionary stages, and theirformation and evolution must have been inﬂuenced by theirenvironments. This is reﬂected in the current spatial andluminosity distributions of each class of Galactic X-ray
sources. Complete X-ray source catalogs in the Galactic plane
become the basis for such statistical studies.
Since the majority of Galactic sources are subject to heavyinterstellar absorption, observations in hard X-rays above a few
keV are essential. Deep imaging observations of the Galactic
plane have been conducted by various X-ray observatories
covering energies above 2 keV, such as ASCA (Sugizaki et al.
2001), Chandra (Ebisawa et al. 2005; Grindlay et al. 2005),
and XMM-Newton (Hands et al. 2004; Nebot Gómez-Morán1

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.
−2skeV−1,
normalization at 1 keV of 10.0 photons cm−9−8which corresponds to 3.98×10 , 1.21×10 , and 8.51×
10−9 erg cm−2 s−1 in the 3–4 keV, 4–10 keV, and 10–20 keVbands, respectively.

for 1 counter and 1 scan. The scan duration of a counter is longer
for a source located closer to the pole of the ISS rotation (Sugizaki
et al. 2011). The effective area of a point source is proportional tocos(f), where f is the photon incident angle along the collimators.
The typical value is ∼5 cm2 at a scan angle of 0° (Sugizaki et al.
2011). For each event, its recorded time and f value (estimatedfrom the detected position along the anode direction and theenergy) are converted into celestial coordinates by referring to theattitude data of MAXI (Sugizaki et al. 2011).
The MAXI/GSC achieves the highest sensitivity in the
4–10 keV band among the previous and on-going all-sky surveys,
such as the Uhuru (Forman et al. 1978), HEAO-1 (Woodet al. 1984), and RXTE slew surveys (Revnivtsev et al. 2004), andis complementary to those in the soft X-ray band below 2 keV(ROSAT: Voges et al. 1999) and above 10 keV (INTEGRAL: Bird
et al. 2007, 2010, 2016; Ebisawa et al. 2003; and Swift:
Baumgartner et al. 2013; Oh et al. 2018). In particular, the4–10 keV band survey has the advantage of detecting X-ray
populations with soft spectra without suffering from absorption aslong as the hydrogen column density is smaller than ∼1023 cm−2.
In addition, MAXI provides us with a unique opportunity to study
the long-term variability of each object, thanks to its almost
continuous all-sky monitoring for >7 years.
While the MAXI/GSC source catalogs in the high-Galacticlatitude region, ∣b∣ > 10, were released by Hiroi et al. (2011)
and Hiroi et al. (2013) from the ﬁrst 7-month and 38-monthdata, respectively, the catalog in the low-latitude region below∣b∣ = 10 has not been produced yet. This is mainly because
the Galactic plane region is heavily crowded with sources andis contaminated by the Galactic Ridge X-ray Emission(GRXE), making it difﬁcult to separate signals from individual
X-ray sources and determine their positions and ﬂuxes
accurately. In this case, it is crucial to accurately estimate thespatial distribution of the GRXE and to reduce systematic
uncertainties in the point-spread function (PSF) of the GSC.
In this paper, we present the ﬁrst MAXI/GSC source catalog
for ∣b∣ < 10 in the 4–10 keV band produced by integrating
the 7 year data from 2009 August 13 to 2016 July 31. We
utilize the same image ﬁtting technique as that employed inthe 37-month catalog (Hiroi et al. 2013). To overcome source
confusion, we calibrate the position-dependent shape of the
GSC PSF and estimate the contribution of the GRXE. We also
determine the 3–4 keV and 10–20 keV ﬂuxes of the individual
detected sources, to calculate their hardness ratios (HRs). For
the remaining sky area (∣b∣ > 10), a new source catalog,
which is an updated version of Hiroi et al. (2013) andcomplementary to ours, will be provided in another paper(T. Kawamuro et al. 2018, in preparation).
Sections 2 and 3 describe the data reduction and analysis,
respectively. The PSF calibration is summarized in the
Appendix. The resultant source catalog and its properties aredescribed in Section 4, and our conclusions are given in
Section 5. We deﬁne the ﬂuxes of the MAXI sources in Crabunits (i.e., relative to the 7-year averaged ﬂux of the Crab
Nebula) unless otherwise stated. The Crab Nebula spectrum isassumed to be an absorbed power-law model,16 with a column
density of 2.6×1021 cm−2, a photon index of 2.1, and a−1

2. Data Reduction
We used the MAXI/GSC cleaned event data version 1.8
from 2009 August 13 to 2016 July 31, and reduced them withessentially the same method as that in the MAXI/GSC 37month high-latitude catalog (Hiroi et al. 2013). The data
reduction was carried out with MXSOFT, which is an original
software package developed by the MAXI team, and Heasoft
version 6.15. We ignored the cameras operated at the nominal
high-voltage levels (1650 V or 1550 V) for only less than
1 year (GSC6, GSC9, GSCa). The GSC0 data after 2013 June
15, when the detector was leaking its gas, were not used either.
We also discarded the data from GSC3, which have large
systematic uncertainties in position calibration and suffer fromhigh background levels due to damage to its veto cells(Sugizaki et al. 2011).
The data screening was performed with mostly the same
selection criteria as those adopted in Hiroi et al. (2013). The
only differences from the previous work were that (1) we foundthat the contamination of the calibration sources is not
negligible in the edge of some GSC counters, and thus
imposed a tighter restriction on the incident angles of photons,∣f∣ < 36 . 8, where the incident angle f is deﬁned by thephoton-detected position on the detector (see Mihara
et al. 2011, for more detail), and that (2) we excluded theevents acquired when the attitude data ﬁles, which are neededin the source/background simulations described below, were
unavailable or contained incorrect values.17 These changes
were made to remove any possible systematic errors and to
improve the sensitivity for detecting faint sources in thecrowded regions on and around the Galactic plane. They only
negligibly affect the results from the previous high-latitude
catalogs.
Figure 1 presents the coverage map created after the data
screening. We utilized the MAXI event simulator “maxisim”(Eguchi et al. 2009), which generates events from X-ray point/
diffuse sources based on the input energy spectra and source
position (and spatial distribution for extended sources).
Referring to the calibration database and the attitude orbit,
and time data included in the auxiliary ﬁles provided by the
MAXI team, it correctly considers the angle dependence ofthe slit area, the collimator ﬁeld of view, and the responses of
the individual GSC cameras. The large-scale patterns seenin the coverage map reﬂect the difference in the duty cycles andthe operation periods of the individual GSC cameras and thedependence of the directions of their ﬁeld of view on the ISS
orbit.
3. Analysis
We performed an image analysis in basically the same way
as that described in Hiroi et al. (2013), fully taking into account17

We ignored the event data taken when (a) the interval of two neighboring attitude data is >60 s, and/or (b) the attitude quaternions of twoneighboring data, q = (q1, q2, q3, q4 ) and q¢ = (q1¢, q2¢, q3¢, q4¢), have unusuallylarge or small differences. For the latter condition, we deﬁned Dq =Si4= 1(qi - qi¢)2  2.5 ´ 10-4 and Δq1.5×10−3, considering the trend
in Δq for the whole period of MAXI operation. The data taken 30 s before andafter the periods with these bad conditions were additionally removed.

16
The spectral parameters are adopted from the INTEGRAL General
Reference Catalog (version 40): http://www.isdc.unige.ch/integral/science/catalogue. One has to bear in mind that the X-ray ﬂux of the Crab Nebula is notconstant (Wilson-Hodge et al. 2011), which could cause a systematic
uncertainty of a few percent levels in the absolute ﬂux calibration.

2

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Figure 1. Coverage map for the 7-year MAXI/GSC data for ∣b∣ < 10 in
Galactic coordinates projected with the Hammer–Aitoff projection. The units
are cm2 s.

Figure 2. Correlations between the VC count rates vs. the 3–20 keV
background event rates of GSC2, when the Russian spacecraft Soyuz was
not present on the docking port close to MAXI. The data are ﬁtted with thefunction f (VC)=a+b/(1 + c × exp(−d(VC − e)), where a∼e are freeparameters. The open circles and squares plot the data when the ISS travels
northward and southward, respectively.

the image response and background contribution. We ﬁrst
divided the entire sky into 768 square regions with a size of
7°. 3×7°. 3 in the sky coordinates (see Hiroi et al. 2013, for thedeﬁnition), whose central positions were determined throughthe Healpix software package (Górski et al. 2005), andproduced tangentially projected images from the screened
event data. We next made the list of source candidates in each
image, and constructed the models of the PSFs of thesesources. Finally, we estimated their positions and ﬂuxes byﬁtting the individual images with the model composed of the
PSFs and the other contributors: the non-X-ray background(NXB), the cosmic X-ray background (CXB), and the GRXE.
The normalizations of the PSFs give the source ﬂuxes in Crabunits, because we measure the total count rates relative to thoseof the PSFs simulated on the basis of the Crab Nebula
spectrum. To make the source search complete, the last two
steps were iterated by including additional sources thatappeared as positive residual signals in the previous image
ﬁtting. We found, however, serious source confusion was
unavoidable in the Galactic center region within ∣b∣ < 5,l<30°, and l>330°. Because faint sources with signiﬁcancesof ∼6.5σ were difﬁcult to detect, we excluded the images inthat region in this image analysis. The complete catalog in thisregion will be provided in a future paper.
Following Hiroi et al. (2013), the data in 4–10 keV, where ahigh signal-to-noise ratio can be achieved, were used to detect
X-ray sources, while energy ﬂuxes in the 3–4 keV and
10–20 keV bands were also estimated for all the detectedsources, to derive their spectral information. In the next
subsections, we describe the details of our analysis, mainly
focusing on the procedures that are different from thoseadopted in Hiroi et al. (2013).

southward. Figure 2 demonstrates the difference in thecorrelation of the background rate and the VC count rate
between the direction of ISS motion; the background rate tends
to be higher when the ISS travels from north to south than it iswhen it travels from south to north. This trend was found to be
seen in all the cameras. More detailed properties of the GSC
background will be described in a future paper (M. Shidatsu
et al. 2018, in preparation).
We produced simulated background data based on our newly
created model, utilizing maxisim. We found that our new
background model improved the reproducibility of the GSC
background strength, especially above ∼5 keV. The simulated
data were processed in exactly the same way as the real event
data, before being used in the image ﬁtting. We produced
10 times more events than what was predicted from the actual
background level, so that the statistical errors in the model
became negligible compared with the real data.
3.2. GRXE ModelingTo detect faint sources in the low-Galactic-latitude region,
we have to estimate the contribution of GRXE accurately. The
GRXE can be separated into two emission components: theGalactic bulge (or bar) and disk (Cooke et al. 1970; Yamauchi& Koyama 1993). Following Revnivtsev et al. (2006), we
modeled these components with an ellipsoid plus disk proﬁle,adopting the parameters given in Table 1 of that work. On thebasis of this model, we created the simulated GRXE data
through maxisim, processed them with the same criteria as thereal data and simulated background data, and incorporated
them in the image analysis. Because the intensity of the GRXE
is much lower than the level of NXB+CXB, we adopted
50 times higher intensity than that of the actual GRXE in thesimulation, to reduce statistical errors. Because this geometricalmodel gives only an approximation of the large-scale proﬁle of
the GRXE, its normalization was left as a free parameter in theimage analysis to allow a small adjustment of its local ﬂux
level. We have conﬁrmed that a constant correction factor overeach image (11° × 11°) improves the ﬁt sufﬁciently well.

3.1. Background Modeling
We constructed the model of the GSC background, by which
we mean the combination of the NXB and the CXB, in thesame manner as Hiroi et al. (2013), using the so-called “VC”
count rate (the rate of the coincident events between a carbon
anode for signal detection and a veto anode) as a tracer of theintensity and energy distribution of the GSC background.
Unlike the previous works, we created the background models
separately for the periods when the ISS moves northward and3

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Table 1
Conversion Factors in the Energy Bands of 3–4 keV, 4–10 keV, and 10–20 keV in Units of 10−11 erg cm−2s−1mCrab−1
Photon Index in Power Law (Γ)
1.0

1.5

1.7

1.9

2.1

2.3

2.5

3.0

3–4 keVlog(NH)=21
log(NH)=22
log(NH)=23

0.409
0.413
0.440

0.404
0.409
0.446

0.402
0.407
0.446

0.399
0.404
0.446

0.396
0.401
0.445

0.392
0.398
0.443

0.389
0.395
0.442

0.380
0.386
0.437

4–10 keV

log(NH)=21
log(NH)=22
log(NH)=23

1.288
1.292
1.330

1.264
1.271
1.323

1.249
1.255
1.312

1.231
1.238
1.298

1.212
1.219
1.282

1.192
1.199
1.265

1.171
1.179
1.247

1.119
1.127
1.200

10–20 keV

log(NH)=21
log(NH)=22
log(NH)=23

0.917
0.918
0.928

0.895
0.896
0.907

0.882
0.883
0.894

0.867
0.868
0.879

0.851
0.852
0.864

0.835
0.836
0.848

0.818
0.819
0.831

0.776
0.777
0.788

on the basis of the Poisson likelihood algorithm (so-called
C-statistics; Cash 1979). We deﬁned the detection signiﬁcancein the 4–10 keV band as

3.3. PSF Modeling, Source Finding, and Position/Flux
Measurements
To minimize the complexity with source confusion, which
is more severe at lower Galactic latitudes, we searched for
new sources after identifying those listed in the Swift/BAT
105 month catalog18 (hereafter BAT105 Oh et al. 2018),
instead of a blind source search as performed by Hiroi et al.
(2013). We adopted the Swift/BAT catalog, which covers thehard X-ray band in 14–195 keV, as a reference catalog,
instead of catalogs in the soft X-ray band below 10 keV,because hard X-rays have stronger penetrating power than soft
X-rays and give a more complete catalog. We ﬁrst prepared
the PSF models for all the sources in the Swift/BAT
105 month catalog by simulating their photon distributions
with maxisim, assuming the same conditions as the actual
observations with the GSC. Here, we used our newly createdcalibration database for the PSF of the GSC (see the Appendix
for details). As the input source positions and spectra, we
adopted the coordinates of the optical counterparts, and forsimplicity, the canonical model of the Crab Nebula (seeSection 1) for all the sources, respectively. We also assumed
that the ﬂux was constant in the PSF simulation; this meansthat we would obtain a time-averaged ﬂux when the source
was variable. We have conﬁrmed that the spectral difference
from the Crab Nebula and the observed time variability has
little effect on the integrated PSF shape and hence does notaffect our results.
We ﬁt the individual images created from the real data, witha model consisting of the background, GRXE, and PSF
components, using the MINUIT package19 in root version
6.06/08. Besides the ﬂuxes of the sources, we also made thenormalization of the background and that of the GRXE freeparameters, to take into account possible small spatial-variationof the ﬂuxes of the CXB and the GRXE (see above). Because
the peak positions of the PSF models could be shifted fromthe actual positions in the GSC images by ∼0°. 05, presumably
due to systematic errors in the alignment of attitude data, weallowed the source positions to vary within 0°. 1 from theoriginal coordinates. The best-ﬁt parameters were determined

sD,4 – 10 keV =(best‐fit 4–10 keV flux),(its 1s statistical error)(1 )where we adopted the “MINOS” negative error calculated with
the MINUIT package for the 1σ error. The ﬂux was obtained in
Crab units, because we basically measure the count rate relative
to that of the Crab Nebula through the PSF ﬁtting.
As a next step, we searched for source candidates that were
not detected in the Swift/BAT catalog, utilizing the residual
map of the previous image ﬁtting, in the same manner as Hiroi
et al. (2013). We smoothed the residual map with a circle ofr=1° with a constant weight of unity, and calculated theexcess-signal signiﬁcance as “St St + Bt ” at each point,where S and B are the count rate of the source and backgroundsignals, respectively, and t is the exposure time. Here, we
adopted a conservative criterion, >4σ, in ﬁnding new source
candidates. We then constructed the PSF models for thosecandidates and added them in the model to be used for the next
image ﬁtting, which determined the detection signiﬁcancesdeﬁned by Equation (1) for all the sources. We repeated theseprocedures (source search, PSF modeling, and image ﬁtting)two times, not to miss any nearby sources, and obtained theﬁnal source list with sD,4 – 10 keV . We ignored, however, thecircular region with a radius of 3° around the Vela supernova
remnant. Because its size is substantially larger than that of the
PSF, signiﬁcant residuals remained after the image ﬁtting and it
was difﬁcult to detect any other sources in that region. Also, inthe ﬁnal catalog we excluded sources detected close to muchbrighter ones if their ﬂux levels were lower than possible
systematic errors in the PSF model of the nearby target (if theﬂux is <1% and <0.4% of the latter at a distance of 1°–2° and
2°–3°, respectively; see the Appendix).
We chose sD,4 – 10 keV = 6.5 as the detection threshold to
reduce the number of fake sources caused by backgroundﬂuctuation (both statistical and systematic ones). In order toestimate it, we searched for negative signals in the smoothed
residual map and performed image ﬁtting to them using
negative PSF models. Assuming that the systematic errors inthe background model are symmetric in positive and negativesides, we estimate that ∼5 spurious sources may be detected in
the Galactic plane region (∣b∣  10) with a signiﬁcance of18

Twelve MAXI sources in our ﬁnal catalog are associated with Swift/BAT
105 month sources that were not detected in the Swift/BAT 70 month catalog(Baumgartner et al. 2013).
19
CERN Program Library Long Writeup D506; https://cern-tex.web.cern.ch/cern-tex/minuit/minmain.html.

4

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Figure 3. Example of our image analysis. The image size is 8°×8° and its center is located at (R.A., decl.)=(107°. 89, −9°. 59). Upper left: the observed image.
Upper right: the smoothed signiﬁcance map (see the text), where the positions of detected sources (No. 48, No. 51, and No. 52) are marked in red. Lower left (right):
the projected image onto the X (Y) axis in the region between the two red (magenta) lines indicated in the upper left panel. The black points represent the data with 1σerrors. The red solid, green dotted, and blue dotted lines represent the best-ﬁt models of the total (PSFs + background), the background (NXB+CXB+GRXE), andthat without the GRXE, respectively.

6.5σ. We note that 11 spurious sources will be found in thecase of sD,4 – 10 keV  6.0 , which is too many to be accepted.
The number of spurious sources was reduced to 3 and 1 in thecase of sD,4 – 10 keV  7.0 and 8.0, respectively.
Figure 3 shows an example of our image analysis. In thisimage, 3 sources are detected with sD,4 – 10 keV > 6.5 (Nos. 48,
51, and 52). We plot the observed image in photon counts, thesmoothed signiﬁcance map, and the projected proﬁles of theobserved image around source No. 48 onto the X and Y axes
with their best-ﬁt models.

3.4. 73-day Sources
To make a complete catalog it is essential to search for transient
sources that are not detected with sD,4 – 10 keV > 6.5 in the 7-year
integrated map. To ﬁnd these transient sources, we applied ourimage analysis method (Section 3.3) to 73-day (i.e., 0.2 year)
integrated GSC images and obtained the light curve of each sourcewith those time bins. We searched for sources with sD,4 – 10 keV >6.5 in the 73-day integrated images, and found 7 additionalsources. Hereafter, we refer to these 7 sources as “73-day sources.”
5

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Table 2
HR1(3–4 keV, 4–10 keV), HR2(4–10 keV, 10–20 keV) in a Power-law-like Spectrum
Photon Index in Power Law (Γ)
1.0

1.5

1.7

1.9

2.1

2.3

2.5

3.0

HR1

log(NH)=21
log(NH)=22
log(NH)=23

0.32
0.35
0.62

0.17
0.20
0.51

0.11
0.15
0.47

0.05
0.09
0.42

−0.01
0.03
0.37

−0.06
−0.02
0.33

−0.11
−0.08
0.28

−0.24
−0.20
0.15

HR2

log(NH)=21
log(NH)=22
log(NH)=23

0.40
0.41
0.48

0.23
0.24
0.33

0.15
0.17
0.27

0.08
0.09
0.20

−0.00
0.01
0.13

−0.08
−0.07
0.05

−0.16
−0.15
−0.03

−0.35
−0.34
−0.21

Table 3
Number of Matched Sources for the 7-year Sources
Catalog Name

BAT1054U

XTEASMLONGXMMSL2MCXC

1RXS

One Catalog Onlya

BAT1054U
XTEASMLONGXMMSL2
MCXC
1RXS

143
L
L
L
L
L

L
4(4)b
L
L
L
L

L
3
8(9)b
L
L
L

L
3
2
12(16)b
L
L

L
1
1
1
8(9)b
L

L
2
2
8
2
14(14)b

143
0
5
7
6
4

L
0
0
0
0(0)b
L

L
0
0
0
0
0(0)b

1
0
3
1
0
0

Number of Matched Sources for the 73-day Sources
BAT1054U
XTEASMLONGXMMSL2
MCXC
1RXS

1
L
L
L
L
L

L
1(1)b
L
L
L
L

L
1
4(4)b
L
L
L

L
0
0
1(1)b
L
L

Notes.
a
Number of MAXI sources matched only with one catalog given in the ﬁrst column.
b
Numbers in parentheses represent those of total matched counterparts in each catalog.

Figure 4. Correlation between the source ﬂux and the detection signiﬁcance forall the 7-year sources (in units of σ), in the 4–10 keV band.

Figure 5. Correlation between the 4–10 keV detection signiﬁcance and the 1σ
positional error of the 71, 7-year sources without BAT105 counterparts.

3.5. Estimation of HR
were ﬁxed at those determined in the analysis for the
4–10 keV data. HRs were deﬁned by the ﬂuxes in any two of
the three bands:

We measured the 3–4 keV and 10–20 keV ﬂuxes of thesources with a signiﬁcance of sD,4 – 10 keV > 6.5 via image
ﬁtting, to obtain their spectral information. The screened
event data, simulated background, GRXE, and PSF data inthe 3–4 keV and 10–20 keV bands were produced in the same
way as those in the 4–10 keV band. The source positions

HR (H, S) =6

FH - FS,
FH + FS(2 )The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Figure 6. Location of the 7-year and 73-day sources in Galactic coordinates. The source ﬂuxes on the logarithmic scale are indicated by the radii of the circles. The
colors represent the object types: blazars and Seyfert galaxies (cyan), galaxy clusters (green), cataclysmic variables (magenta), stars (sky blue), pulsars (blue),supernova remnants (pink), high-mass, and low-mass X-ray binaries (red and orange, respectively), X-ray binaries (purple), sources whose types are unidentiﬁed in
BAT105, 4U, XTEASMLONG, and XMMSL2 (black), and sources without any counterparts (gray).

Figure 7. Scatter plots of HRs to the 4–10 keV ﬂux (Upper panel). The colors represent the object types: blazars, galaxy clusters, and Seyfert galaxies (green),supernova remnants and pulsars (blue), cataclysmic variables and stars (sky-blue), X-ray binaries (red), and unidentiﬁed and unmatched sources (black). The 73-daysources are indicated by the cross marks.

where FH and FS correspond to the ﬂuxes in the higher andlower energy bands, respectively. For the 73-day sources, we
adopted the ﬂuxes in one of the 73-day time bins when the
4–10 keV ﬂux was the highest (the column (15) of Table 5).
We deﬁned HR1 as that between the 4–10 keV and 3–10 keVbands, and HR2 between the 10–20 keV and 4–10 keV bands.

provide the 7-year MAXI/GSC catalog in the Galactic plane
region ∣b∣ < 10 (except for the Galactic center region ∣b∣ < 5
and ∣l∣ < 30), obtained from the GSC data in the 4–10 keVband. We detected 214 sources in total, with a signiﬁcance ofsD,4 – 10 keV > 6.5 in the 7-year integrated image, 143 of which
are identiﬁed with sources listed in BAT105. Hereafter, these214 sources are referred to as the “7-year sources.” Seven
sources are additionally detected in the 73-day time-sliced
images (“73-day sources”; Table 5), one of which is identiﬁed
with BAT105. The lowest source ﬂux above sD,4 – 10 keV = 6.5
in the 7-year integrated image is 0.43 mCrab, which

4. Catalog
In this section, we present the catalog and discuss thestatistical properties of the detected sources. In Table 4, we
7The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Figure 8. (a) 7-year light curves with 73-day bins. The mean ﬂux of each source is plotted with a red dotted line. Flux margins are cut off at a ﬂux of zero, sometimes
resulting in small vertical error bars because the best-ﬁt ﬂux value is below zero. (b) 7-year light curves for 73-day sources with 73-day bins. The mean ﬂux of eachsource is plotted with a red dotted line. Flux margins are cut off at a ﬂux of zero, sometimes resulting in small vertical error bars because the best-ﬁt ﬂux value isbelow zero.

8

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Figure 8. (Continued.)

9The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 8. (Continued.)

10

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 8. (Continued.)

11

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 8. (Continued.)

12

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 8. (Continued.)

13

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 8. (Continued.)

14

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 8. (Continued.)

15

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 8. (Continued.)

16

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Figure 8. (Continued.)corresponds to 5.2×10−12 erg cm−2s−1 in the 4–10 keVband for a Crab-like spectrum. Note that the conversion factor
from a ﬂux in Crab units to a physical unit depends on the
spectral shape. Table 1 summarizes those factors for various
combinations of parameters of an absorbed power-law model.
The corresponding values of HR1 and HR2 are listed inTable 2 (by deﬁnition HR1=0 and HR2=0 for a Crab-like
spectrum).
Figure 4 shows the correlation between the 4–10 keV ﬂux
and the detection signiﬁcance sD,4 – 10 keV for the 7-year
sources. The observed trend can be understood by considering that the detection signiﬁcance is approximately expressed
as sD,4 – 10 keV ~ St St + Bt . At low ﬂuxes, background
events are dominant (sD,4 – 10 keV ~ S t B ), and hence we
predict a linear correlation. By contrast, the source counts are
dominant at high ﬂuxes, sD,4 – 10 keV should be proportional to
the square root of the source counts; sD,4 – 10 keV ~ St . The
data in Figure 4 indeed follow the trend. Note that ourapproximation of sD,4 – 10 keV ~ St St + Bt does not represent the statistical signiﬁcance of deviation from the background level in the source-photon-limited case. There are a
few tens of sources that deviate from the trend and haverelatively small detection signiﬁcances, due to contamination
by nearby bright sources.

X-ray catalogs. We ﬁrst matched the Uhuru fourth catalog(Forman et al. 1978, hereafter 4U) and found the counterpartsof four sources. Then, we searched the RXTE All-Sky Monitor(ASM) long-term observed source table (hereafter XTEASMLONG), which is based on ASM light curve data products20 for
the remaining sources that have no counterparts in BAT105
and 4U. Finally, we carried out cross-matching with the XMMNewton slew survey catalog (hereafter XMMSL2; Saxton
et al. 2008), the Meta-Catalog of X-ray Detected Cluster of
Galaxies (hereafter MCXC; Piffaretti et al. 2011), and the
ROSAT all-sky survey bright source catalog (hereafter 1RXS;
Voges et al. 1999). For XMMSL2 and 1RXS, we only referredto the sources with ﬂuxes of >1.0×10−12 erg cm−2 s−1 and>0.30 cts s−1, respectively, both corresponding to 0.3 mCrab
for the Crab spectrum. Finally, as for the sources with BAT105
counterparts that are optically unidentiﬁed (“unidentiﬁed”) andthose without BAT105 counterparts that are not matched withany objects in the above 5 X-ray catalogs (“unmatched”), we
also checked the MAXI transient source catalog summarized
by Negoro et al. (2016).
As a result, 36 out of the 77 sources were matched with at least
1 counterpart. Tables 3(a) and (b) show the number of MAXI
sources that were matched with the reference catalogs for the
7-year and 73-day sources, respectively. Tables 6 and 7 list thecounterparts for 7-year and 73-day sources, respectively. If
multiple sources were found within the error circles, we adopted
the closest object to the position in our catalog as the most likely
counterpart. For BAT105 sources, we did not attempt to ﬁnd
counterparts in other catalogs, because their positional errors were
not estimated. The typical positional errors of the 4U, XMMSL2,
and 1RXS counterparts are 0°. 5, 3″, and 10″ respectively. The
expected numbers of erroneous identiﬁcation by chance are
estimated to be 0.88, 1.48, 1.78, 0.31, and 2.45 for 4U,
XTEASMLONG, XMMSL2, MCXC, and 1RXS, respectively,
based on the mean number densities of the cross-matched sourcesin our survey region and the total area of the error circles (2.5σ) of
the MAXI sources without BAT105 counterparts. Figure 6 plots
the location of the MAXI sources in Galactic coordinates. Table 8(second column) lists the number of each source type. The ﬂuxesof the MAXI sources were found to be consistent with those of
their counterparts in 4U, XTEASMLONG, XMMSL2, MCXC,
and 1RXS catalogs within a factor of 4. In Figure 7, we present
the correlation between the 4–10 keV ﬂux and the HR (HR1 or
HR2), and that between HR1 and HR2, for different object types.

4.1. Cross-matching with Other X-Ray Catalogs
For statistical studies of cataloged sources, it is important toﬁnd the counterparts and identify the object types of thedetected sources. For this purpose, it is necessary to estimate
the position accuracy of the detected sources. Figure 5 plots thedetection signiﬁcance in the 4–10 keV band and the 1σ
positional errors of the 71, 7-year sources that are not listed
in BAT105. They are roughly inversely proportional, as
expected from statistics in determining the center of the PSF
with limited source counts. The typical 1σ error at
sD,4 – 10 keV ~ 7 is ∼0°. 2.
As a next step, we attempted to identify the sources without
BAT105 counterparts, using other catalogs. The positional22+ s syserror σposi is deﬁned as sposi º s stat
, where σstat andσsys are the statistical and systematic errors, respectively. We
adopted σsys=0°. 05, which is a typical systematic uncertainty
associated with GSC alignment calibration (Hiroi et al. 2011).
We searched for sources in the reference catalogs locatedwithin a 2.5σposi error circle, which corresponds to the 95%
conﬁdence level. We utilized the data when the highest
4–10 keV ﬂux was obtained among the individual 73-day bin
images to estimate σstat for the 73-day sources (Table 5).
Because of the large positional errors, it is difﬁcult to ﬁnd thecounterparts in optical or infrared catalogs, which have a muchhigher number density of sources with a much better position
accuracy. We therefore performed cross-matching with major

4.2. Time Variabilities
Long-term variability is essential information for understanding the nature of the detected objects. Figures 8(a) and (b)show the light curves for all objects. We added a systematic
error of 1.6% in each ﬂux due to incomplete instrumental
20

17

https://heasarc.gsfc.nasa.gov/W3Browse/xte/xteasmlong.html

18

(2)
3MAXI

(3)
R.A.

(4)
Decl.

(5)
σstata(6)
sD,4 – 10 keV(7)
f4 – 10keV b(8)
sD,3 – 4 keV(9)f3 - 4 keV c(10)
sD,10 – 20 keV(11)f10 – 20keV d

(12)
HR1e

(13)
HR2f

(14)
s 2rms g

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47

J0000+674
J0025+641
J0029+592
J0035+598
J0036+614
J0056+606
J0117+652
J0118+637
J0140+583
J0146+616
J0210+525
J0227+619
J0241+611
J0244+624
J0252+571
J0334+531
J0342+636
J0404+572
J0408+632
J0418+380
J0427+354
J0441+445
J0450+450
J0452+496
J0456+523
J0457+455
J0459+272
J0525+241
J0534+220
J0534+285
J0538+263
J0547+379
J0601+130J0602+285
J0602+230
J0605+299
J0616+225
J0617+091
J0631+251
J0633+049
J0635+225
J0635+077
J0640−127
J0641+098
J0645−169
J0648+152
J0656−035

0.006
6.308
7.280
8.938
9.082
14.15519.49219.56625.07226.54332.50936.84540.35441.19043.09953.69655.60661.18762.16364.52266.75770.28972.50573.13874.06574.42874.87481.451
83.62483.62784.73286.90290.44390.65990.71091.25394.15594.27897.86398.42398.85198.941
100.133
100.416101.415102.211104.00767.44964.13259.25259.80261.41760.69265.26863.71158.31961.65152.51261.91861.13762.41857.19053.14763.60857.28763.21238.05535.47144.58945.03749.64352.36745.51727.20224.12422.01228.55726.30937.92913.00928.57323.05229.98822.576
9.137
25.176
4.949
22.5277.764−12.7889.850−16.91015.273−3.599

0.173
L
L
L
L
L
L
L
0.121
L
L
0.153
L
L
0.094
L
0.099
0.203
0.219
L
0.102
L
0.022
L
0.090
L
L
L
L
L
L
L
0.156
L
0.166
0.076
0.100
L
0.128
0.112
L
0.091
L
0.054
L
0.108
0.159

7.2
51.9
8.2
10.2
14.4
101.9
61.8
43.5
8.1
26.7
11.9
8.1
7.2
22.0
8.5
75.3
12.5
6.5
6.5
31.8
11.7
15.6
56.8
9.2
13.4
9.5
8.3
20.8
2222.4
9.0
296.3
8.0
7.9
24.7
6.9
16.3
11.7
383.5
9.1
9.8
27.6
12.3
9.2
6.5
7.1
10.0
6.9

6.3±0.9
52.1±1.0
28±346±415.6±1.1
113.3±1.174.3±1.253.5±1.2
8.0±1.0
27.1±1.0
24±27.9±1.0
8.7±1.2
22.6±1.0
8.8±1.0
96.4±1.3
11.4±0.96.8±1.0
5.9±0.9
37.2±1.2
13.0±1.1
21.7±1.483.0±1.510.7±1.215.7±1.2
13.4±1.4
8.2±1.0
21.5±1.012494±69.1±1.0
444.3±1.5
9.0±1.1
7.6±1.0
25.6±1.0
7.2±1.0
17.8±1.1
11.3±1.0606.6±1.68.9±1.0
8.9±0.9
27.6±1.0
11.7±1.0
7.5±0.8
6.3±1.0
8.3±1.2
10.2±1.0
6.2±0.9

6.5
80.4
11.6
32.3
9.3
72.0
34.0
19.6
4.1
50.0
20.5
5.1
8.1
16.6
3.8
28.0
9.7
6.4
3.9
27.4
12.6
13.6
58.9
8.8
15.9
10.9
4.4
20.4
1507.1
2.9
153.3
9.1
9.9
18.5
9.3
19.4
42.4
306.4
7.9
10.3
26.3
8.8
10.6
5.5
10.0
11.4
4.4

1.7±0.3
30.9±0.44.6±0.4
14.1±0.4
3.0±0.3
27.5±0.4
11.2±0.3
6.5±0.3
1.2±0.3
18.0±0.4
7.5±0.4
1.5±0.3
2.7±0.3
5.4±0.3
1.2±0.3
10.4±0.4
2.7±0.3
2.0±0.3
1.1±0.3
9.7±0.4
4.1±0.3
5.0±0.4
26.8±0.5
3.0±0.3
5.6±0.4
4.1±0.4
1.2±0.3
6.4±0.3
3980±30.8±0.3
74.9±0.5
3.0±0.3
2.7±0.3
6.2±0.3
2.6±0.3
6.5±0.3
13.5±0.3
206.4±0.7
2.2±0.3
2.7±0.3
7.9±0.3
2.3±0.3
2.4±0.2
1.5±0.3
2.2±0.2
3.3±0.3
1.1±0.2

0.0
4.3
6.8
7.3
1.7
22.9
23.1
16.1
2.0
3.5
5.6
0.0
1.1
7.4
2.8
42.3
1.2
1.5
0.0
6.6
1.8
3.2
6.5
3.2
1.3
1.9
3.1
0.0
997.7
0.0
141.9
2.5
0.0
5.8
1.2
0.0
1.1
73.0
0.0
1.9
3.3
0.0
1.3
0.0
1.9
1.0
3.1

<1.7
15±431±534±56.7±3.985±485±461±47.5±3.8
13±425±4<5.5
4.3±4.0
28±411.2±4.0
192±44.0±3.5
6.1±3.9<4.6
28±47.5±4.1
14±431±514±45.4±4.3
9.2±4.7
12±4<4.68510±8<4.4616±4
10.6±4.2<2.7
23±44.4±3.7<5.0
4.0±3.6259±4<2.3
6.2±3.3
12±4<5.9
3.9±3.1<6.3
5.8±3.0
3.9±3.8
10±30.08±0.13−0.30±0.01
0.32±0.11
0.02±0.06
0.24±0.07
0.14±0.01
0.36±0.02
0.45±0.03
0.35±0.14−0.35±0.02
0.01±0.06
0.25±0.13
0.02±0.11
0.14±0.04
0.40±0.14
0.49±0.02
0.14±0.08
0.05±0.13
0.27±0.17
0.10±0.03
0.00±0.07
0.16±0.06−0.01±0.01
0.06±0.10−0.05±0.06
0.03±0.09
0.35±0.14
0.03±0.04
0.00±0.00
0.55±0.15
0.31±0.00−0.02±0.10−0.05±0.10
0.14±0.04−0.06±0.11−0.07±0.05−0.58±0.03−0.03±0.00
0.13±0.10
0.03±0.09
0.06±0.03
0.23±0.08−0.00±0.09
0.15±0.14
0.09±0.11−0.00±0.08
0.29±0.15−1.0±0.2−0.40±0.09
0.24±0.13
0.05±0.10−0.2±0.3
0.05±0.03
0.25±0.03
0.25±0.05
0.2±0.4−0.17±0.15
0.20±0.14−0.50±0.12−0.2±0.50.30±0.11
0.3±0.3
0.49±0.02−0.3±0.4
0.1±0.5−0.57±0.16
0.04±0.10−0.1±0.3−0.0±0.2−0.29±0.07
0.3±0.3−0.3±0.3
0.0±0.3
0.4±0.3−0.88±0.06
0.00±0.00−0.86±0.14
0.34±0.01
0.3±0.3−1.00±0.18
0.13±0.12−0.1±0.5−0.88±0.08−0.3±0.4−0.23±0.01−1.00±0.16
0.0±0.3−0.22±0.15−0.52±0.08−0.1±0.4−0.22±0.12
0.0±0.3−0.3±0.4
0.4±0.3

0.14±0.13−0.005±0.005
0.05±0.02
0.441±0.007−0.00±0.04
0.011±0.002
0.031±0.003
13.081±0.006
0.23±0.09
0.01±0.02
0.00±0.02
0.15±0.09
0.20±0.08
0.07±0.02
0.15±0.07
18.699±0.008−0.04±0.06
0.29±0.09−0.07±0.12
0.02±0.01−0.01±0.05
2.41±0.03−0.005±0.003−0.03±0.07
0.12±0.05
0.01±0.07
0.15±0.07
0.02±0.02−0.000±0.000
0.34±0.06
8.004±0.005
1.51±0.06
0.30±0.06
0.00±0.03−0.05±0.10−0.01±0.03
0.05±0.05
0.023±0.001
0.08±0.08−0.04±0.07−0.02±0.01
0.03±0.06
0.07±0.07
0.39±0.14
0.02±0.06
0.19±0.07
0.35±0.08

Hori et al.

(1)
No.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Table 4
Properties of the 7-year Sources in the MAXI/GSC Catalog at ∣b∣ < 10

19

(2)
3MAXI

(3)
R.A.

(4)
Decl.

(5)
σstata(6)
sD,4 – 10 keV(7)
f4 – 10keV b(8)
sD,3 – 4 keV(9)f3 - 4 keV c(10)
sD,10 – 20 keV(11)f10 – 20keV d

(12)
HR1e

(13)
HR2f

(14)
s 2rms g

48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94

J0704−114
J0708−155
J0714−254
J0717−114
J0725−064
J0728−206
J0729−262
J0733−135
J0745−162
J0747−192
J0752−442
J0753−459
J0758−221
J0759−387
J0802−496
J0804−276
J0809−406
J0823−430
J0839−358
J0841−562
J0844−378
J0902−481
J0902−405
J0910−526
J0916−623
J0920−552
J0922−632
J1009−582
J1018−582
J1031−621
J1036−568
J1038−497
J1044−596
J1121−606
J1139−653
J1141−639
J1144−698
J1144−610
J1147−619
J1156−566
J1203−538
J1213−648
J1226−627
J1235−646
J1237−667
J1240−577
J1243−630

106.045107.249108.644109.309111.473112.129112.269
113.259
116.465
116.919118.198
118.425119.596119.857
120.649
121.109122.309125.758
129.758130.295
131.231135.505135.533
137.637
139.008140.104
140.749
152.426
154.582
157.773
159.210159.736161.220170.292
174.766
175.434
176.133
176.158
176.829179.019180.868
183.349186.642188.792
189.312190.168
190.931−11.418−15.551−25.445−11.476−6.451−20.696−26.205−13.568−16.220−19.257−44.215−45.974−22.103−38.721−49.679−27.681−40.676−43.052−35.899−56.247−37.834−48.130−40.550−52.606−62.309−55.216−63.268−58.285−58.207−62.152−56.848−49.762−59.694−60.629−65.399−63.966−69.820−61.042−61.978−56.675−53.844−64.844−62.789−64.667−66.722−57.791−63.076

0.162
L
L
0.053
0.155
0.150
L
L
L
L
0.150
0.170
0.097
L
L
0.138
0.143
0.070
L
0.203
0.078
L
L
L
L
L
L
L
0.080
0.132
L
L
L
L
L
0.155
L
L
L
0.090
L
L
L
L
0.117
L
L

6.9
12.9
7.2
21.0
8.2
7.4
20.0
12.7
13.0
48.3
7.9
7.0
11.7
14.3
10.1
8.2
8.0
15.3
8.4
6.7
14.6
13.3
564.2
6.7
10.3
128.7
19.6
108.4
12.2
6.9
10.1
6.9
34.8
658.8
32.1
8.4
7.1
14.0
121.9
9.2
12.0
82.3
419.1
31.9
10.6
9.7
19.9

5.7±0.8
10.5±0.8
6.0±0.8
17.8±0.8
7.1±0.9
6.0±0.8
16.8±0.810.4±0.810.5±0.840.9±0.88.4±1.1
7.6±1.1
9.5±0.8
13.7±1.0
9.9±1.0
6.9±0.8
8.0±1.0
16.6±1.1
8.0±1.0
5.5±0.8
13.9±0.914.3±1.11170±26.5±1.0
13.2±1.3
130.3±1.0
41±2
195.2±1.820.5±1.75.3±0.88.6±0.9
6.5±1.0
57.1±1.6
1090.2±1.749.0±1.5
7.1±0.8
5.2±0.7
19.5±1.4
151.9±1.2
7.6±0.8
10.6±0.972.1±0.9
591.6±1.427.5±0.9
8.0±0.8
10.6±1.119.8±1.0

5.0
15.7
7.1
17.9
6.7
7.9
13.6
5.6
10.9
45.1
6.8
2.3
11.2
9.3
7.2
5.5
5.9
66.9
7.6
5.4
11.3
9.9
204.0
5.6
14.0
116.0
35.0
80.4
21.6
3.5
5.6
3.8
64.3
300.6
58.3
3.3
7.8
11.7
49.5
8.7
8.0
55.9
69.6
10.9
8.9
10.4
10.3

1.1±0.2
3.6±0.2
1.6±0.2
4.3±0.2
1.6±0.2
1.8±0.2
3.2±0.2
1.2±0.2
2.4±0.2
11.4±0.38±10.7±0.3
2.5±0.2
2.5±0.3
2.0±0.3
1.2±0.2
1.6±0.3
93±11.9±0.3
1.3±0.2
3.0±0.3
3.1±0.3
112.3±0.6
1.5±0.3
3.8±0.3
41.7±0.49.9±0.3
29.0±0.4
7.4±0.3
0.8±0.2
1.5±0.3
1.0±0.3
22.4±0.3
167.8±0.617.1±0.3
1.0±0.3
1.8±0.2
4.1±0.4
19.8±0.4
2.1±0.2
2.1±0.3
16.5±0.325.4±0.4
3.0±0.3
2.1±0.2
2.7±0.3
3.3±0.3

0.0
3.0
0.0
0.0
2.8
1.3
5.5
4.7
5.2
5.6
2.4
0.0
0.0
2.0
2.9
1.6
1.3
1.9
3.4
1.7
0.0
1.6
371.2
0.0
4.6
21.0
3.2
61.7
1.0
1.2
3.9
0.0
5.2
337.5
7.3
0.0
1.9
6.4
42.0
0.0
2.9
11.7
353.0
12.9
0.0
5.3
2.1

<3.8
9±3
<4.8
<9.9
8.9±3.1
4.0±3.1
17±314±316±317±336.7±15.1
<4.6
<3.9
7.2±3.5
10.4±3.6
5.1±3.1
4.6±3.7
26.8±13.8
12±35.5±3.1<5.8
6.3±4.02027±6<5.8
14±369±310±3225±43.8±3.7
3.4±2.8
12±3<5.6
18±41398±421±3<4.8
4.8±2.625±4179±4<2.6
9.7±3.3
33±3
1580±439±3<3.6
17±37.2±3.5

0.23±0.14−0.04±0.06
0.09±0.12
0.14±0.04
0.17±0.12
0.04±0.11
0.25±0.05
0.45±0.10
0.16±0.07
0.07±0.02−0.49±0.15
0.56±0.19
0.09±0.08
0.28±0.07
0.22±0.10
0.27±0.13
0.22±0.12−0.89±0.02
0.14±0.11
0.14±0.14
0.20±0.07
0.20±0.07
0.54±0.00
0.17±0.14
0.05±0.07−0.00±0.01
0.14±0.04
0.36±0.01−0.06±0.06
0.34±0.17
0.30±0.11
0.34±0.16−0.10±0.02
0.35±0.00−0.05±0.02
0.41±0.15−0.03±0.12
0.20±0.07
0.42±0.01
0.06±0.10
0.24±0.09
0.16±0.01
0.76±0.00
0.49±0.04
0.09±0.09
0.10±0.09
0.31±0.06−0.69±0.16
0.1±0.2−0.45±0.13−0.28±0.04
0.3±0.3−0.0±0.5
0.20±0.14
0.34±0.18
0.38±0.17−0.25±0.08
0.7±0.5−0.82±0.18−0.77±0.10−0.1±0.3
0.2±0.3
0.0±0.4−0.1±0.5
0.4±0.5
0.4±0.3
0.2±0.4−0.61±0.07−0.2±0.3
0.44±0.00−0.30±0.12
0.23±0.17−0.13±0.03−0.48±0.12
0.26±0.01−0.6±0.3−0.0±0.5
0.3±0.2−0.37±0.12−0.36±0.08
0.31±0.00−0.22±0.07−0.49±0.11
0.1±0.4
0.30±0.13
0.27±0.02−1.00±0.15
0.1±0.2−0.19±0.04
0.59±0.00
0.35±0.07−0.73±0.11
0.40±0.17−0.3±0.2

0.02±0.11
0.28±0.04−0.12±0.10−0.01±0.02
0.04±0.08
0.21±0.07
0.11±0.02−0.12±0.05
0.06±0.04−0.003±0.005
0.07±0.08
0.33±0.08−0.03±0.05
0.09±0.04−0.00±0.07
0.01±0.10
0.32±0.07
0.02±0.03
0.10±0.06
0.27±0.10−0.00±0.04
0.05±0.04
0.015±0.001
0.07±0.09
0.12±0.03
0.156±0.001
0.013±0.006
5.229±0.004
0.09±0.02
0.17±0.08
0.59±0.03
0.09±0.09
0.131±0.003
0.205±0.001
0.101±0.004
0.25±0.07
0.17±0.09
0.09±0.03
0.037±0.001
0.00±0.09−0.00±0.06
1.011±0.003
0.020±0.001
0.012±0.010
0.13±0.07
0.19±0.04
0.04±0.02

Hori et al.

(1)
No.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Table 4
(Continued)

20

(2)
3MAXI

(3)
R.A.

(4)
Decl.

(5)
σstata(6)
sD,4 – 10 keV(7)
f4 – 10keV b(8)
sD,3 – 4 keV(9)f3 - 4 keV c(10)
sD,10 – 20 keV(11)f10 – 20keV d

(12)
HR1e

(13)
HR2f

(14)
s 2rms g

95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141

J1249−590
J1257−692
J1301−615
J1302−639
J1314−602
J1317−629
J1325−577
J1326−621
J1331−549
J1345−623
J1347−606
J1356−645
J1359−633
J1407−618
J1412−653
J1419−610
J1420−626
J1423−541
J1442−626
J1446−641
J1449−598
J1453−553
J1455−516
J1502−601
J1509−667
J1513−461
J1514−591
J1520−571
J1533−658
J1542−523
J1547−625
J1548−455
J1548−476
J1551−543
J1601−607
J1612−607
J1617−595
J1629−613
J1640−324
J1641−346
J1650−601
J1650−330
J1653−593
J1655−519
J1702−299
J1709−266
J1710−280

192.401
194.396195.300
195.602
198.672
199.432201.279
201.616202.914206.256206.840209.147209.958
211.782
213.095214.835
215.199215.977220.687
221.687
222.369
223.284
223.981225.726227.378228.479228.532
230.129233.309235.573236.951
237.126
237.229237.910240.313243.168
244.460
247.312250.222250.358
252.530252.549
253.365
253.995
255.506
257.424
257.543−59.071−69.292−61.595−63.908−60.240−62.995−57.725−62.147−54.947−62.382−60.648−64.503−63.352−61.891−65.310−61.011−62.680−54.177−62.635−64.128−59.808−55.389−51.673−60.182−66.723−46.122−59.124−57.195−65.862−52.373−62.563−45.505−47.698−54.399−60.750−60.732−59.558−61.314−32.469−34.670−60.154−33.018−59.328−51.965−29.978−26.605−28.084

L
L
L
L
0.162
L
0.053
L
0.122
0.089
L
0.069
L
L
L
L
L
0.158
0.039
L
L
L
L
L
L
0.084
L
L
0.133
L
L
L
0.135
L
L
L
L
0.161
0.095
0.141
0.065
L
L
L
0.043
L
L

62.1
431.0
371.1
40.9
8.3
10.7
22.3
67.9
9.9
13.4
17.9
12.8
13.8
23.1
20.7
21.1
40.8
7.6
30.3
8.7
15.9
23.1
9.8
9.9
16.5
13.8
87.6
395.5
8.3
179.4
373.0
21.6
9.0
17.9
64.3
82.1
8.6
7.3
7.4
8.2
17.1
11.8
16.1
14.8
26.3
68.1
41.1

69.1±1.1
504.4±1.2
479.9±1.338.9±1.0
7.0±0.8
16.3±1.518.7±0.8
123.6±1.88.7±0.9
13.1±1.032.9±1.8
28±2
13.7±1.0
25.0±1.1
22.1±1.1
22.4±1.140.8±1.0
6.8±0.9
25.4±0.8
6.8±0.8
15.7±1.026.2±1.1
9.2±0.99.5±1.0
12.4±0.8
15.0±1.1
91.9±1.0
574.2±1.5
6.2±0.8
209.4±1.2
447.7±1.2
28.2±1.3
9.7±1.1
20.4±1.1
203±3
112.4±1.4
12.4±1.4
7.3±1.0
6.4±0.9
7.3±0.9
20.7±1.2
10.9±0.926.3±1.6
14.4±1.0
23.6±0.979.3±1.2
46.8±1.1

75.9
325.5
180.1
21.0
7.9
20.4
33.7
66.8
7.0
13.9
27.3
27.5
8.7
11.9
10.9
9.5
20.6
10.0
45.4
1.1
4.6
19.9
10.4
4.8
4.4
14.6
70.0
255.2
5.5
87.0
272.9
15.8
4.7
8.4
136.3
108.8
12.4
15.8
5.1
3.0
19.2
7.5
23.8
12.8
25.5
74.6
41.0

23.8±0.3
161.1±0.578.8±0.46.9±0.3
2.2±0.3
7.2±0.4
9.2±0.3
24.8±0.4
1.8±0.3
4.7±0.3
8.0±0.3
8.5±0.3
2.9±0.3
4.0±0.3
2.7±0.3
3.5±0.4
6.6±0.3
2.7±0.3
13.2±0.3
0.3±0.3
1.5±0.3
5.5±0.3
2.9±0.3
1.4±0.3
1.0±0.2
4.6±0.3
26.6±0.4
152.4±0.6
4.5±0.8
32.8±0.4
133.9±0.54.9±0.3
1.4±0.3
3.3±0.4
57.9±0.447.4±0.4
3.9±0.3
4.2±0.3
1.3±0.2
0.7±0.2
6.5±0.3
1.9±0.3
8.3±0.3
3.8±0.3
7.0±0.3
25.4±0.312.7±0.3

12.7
65.1
146.7
12.7
1.8
1.1
0.0
30.5
0.0
0.0
11.2
9.6
2.5
4.8
14.0
5.9
17.2
0.0
2.7
4.1
3.5
8.8
2.5
2.0
5.5
0.0
21.1
54.7
3.6
81.6
52.5
8.1
1.8
4.2
20.7
15.3
2.4
3.3
0.0
1.4
2.4
4.1
3.3
5.3
4.8
10.8
10.4

39±3177±3523±441±35.5±3.1
3.9±3.4<4.5
106±4<6.3<4.2
35±332±39.0±3.6
17±439±323±455±3<6.2
8.2±3.0
12±312±329±38.9±3.5
6.4±3.1
15±3<1.7
69±3208±427±8304±4157±3
32±47.4±4.0
17±466±355±48.1±3.4
10±3<6.5
4.7±3.3
9.6±4.0
14±313±419±416±336±335±3−0.04±0.01−0.00±0.00
0.32±0.00
0.29±0.03
0.02±0.11−0.16±0.06−0.22±0.03
0.23±0.01
0.20±0.10−0.06±0.06
0.14±0.04
0.02±0.05
0.20±0.08
0.33±0.05
0.44±0.05
0.35±0.06
0.33±0.03−0.11±0.10−0.24±0.02
0.76±0.19
0.53±0.09
0.21±0.04
0.01±0.09
0.36±0.12
0.60±0.09
0.02±0.06
0.05±0.01
0.09±0.00−0.38±0.17
0.34±0.01
0.03±0.00
0.30±0.05
0.37±0.13
0.33±0.07
0.06±0.01−0.14±0.01
0.01±0.09−0.28±0.08
0.24±0.14
0.53±0.16
0.00±0.05
0.30±0.09
0.01±0.05
0.09±0.06
0.04±0.03−0.00±0.01
0.08±0.02−0.09±0.05−0.32±0.01
0.23±0.01
0.22±0.06
0.1±0.4−0.5±0.3−0.80±0.05
0.11±0.02−0.33±0.08−0.88±0.10
0.22±0.07
0.26±0.09−0.0±0.2
0.00±0.13
0.44±0.07
0.20±0.13
0.33±0.05−0.23±0.10−0.36±0.15
0.4±0.2
0.05±0.19
0.23±0.09
0.2±0.3−0.0±0.3
0.27±0.14−1.00±0.10
0.05±0.03−0.30±0.01
0.7±0.3
0.36±0.01−0.32±0.01
0.25±0.10
0.1±0.4
0.10±0.16−0.35±0.02−0.16±0.03−0.0±0.3
0.3±0.3−0.15±0.10−0.0±0.4−0.2±0.2
0.3±0.2−0.15±0.17
0.32±0.16−0.02±0.13−0.20±0.05
0.05±0.06

0.338±0.002
0.001±0.000
1.444±0.002
0.114±0.005
0.21±0.07
0.03±0.01−0.02±0.02
0.024±0.001
0.18±0.06−0.01±0.02
0.027±0.007
7.967±0.009
0.04±0.04
1.48±0.01
0.01±0.01
0.03±0.01
5.236±0.009−0.09±0.11−0.01±0.01−0.00±0.09
0.13±0.03
0.25±0.01
0.14±0.06
0.21±0.05
0.09±0.04−0.03±0.05
0.008±0.002
3.712±0.004
0.41±0.07
0.003±0.001
0.043±0.001
0.04±0.02
0.18±0.07
0.11±0.05
0.001±0.001
0.000±0.001
0.07±0.05
0.00±0.03
0.25±0.09
0.10±0.09
0.01±0.02
0.07±0.04
0.03±0.02
0.00±0.05
7.846±0.008
8.776±0.004
0.046±0.005

Hori et al.

(1)
No.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Table 4
(Continued)

21

(2)
3MAXI

(3)
R.A.

(4)
Decl.

(5)
σstata(6)
sD,4 – 10 keV(7)
f4 – 10keV b(8)
sD,3 – 4 keV(9)f3 - 4 keV c(10)
sD,10 – 20 keV(11)f10 – 20keV d

(12)
HR1e

(13)
HR2f

(14)
s 2rms g

142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188

J1712−233
J1713−241
J1730−215
J1731−169
J1738−444
J1741−122
J1750−370
J1803−344
J1806−089
J1807−369
J1810−041
J1814+022
J1823−347
J1823−303
J1825−000
J1828−253
J1829−238
J1834−210
J1836−194
J1839+050
J1849−171
J1855−026
J1855+157
J1858+033
J1858+082
J1901+014
J1904−108
J1904−131
J1910+097
J1910−057
J1910+076
J1911+005
J1911+049
J1915+109
J1918−052
J1928+204
J1929+184
J1930+096
J1941+301
J1941+258
J1942+224
J1944+212
J1945+274
J1946+449
J1949+301
J1955+321
J1958+352

258.079258.262262.564262.935
264.728265.477
267.548270.927271.656271.989272.576273.502275.824275.914276.352
277.249277.362278.523
279.039279.994
282.420283.869
283.900
284.579
284.656285.442286.119286.205
287.509287.560
287.675
287.824
287.989288.806
289.707292.148292.377292.713295.322295.488295.602296.092
296.365296.688297.423298.885299.596−23.333−24.146−21.579−16.961−44.445−12.244−37.062−34.422−8.967−36.943−4.1602.201−34.796−30.358−0.012−25.355−23.817−21.081−19.400
5.029−17.163−2.60715.733
3.335
8.261
1.475
−10.885−13.166
9.729−5.760
7.684
0.577
4.939
10.938−5.23220.41118.411
9.692
30.18325.86122.46621.20727.41044.92030.16032.11635.201

L
L
L
L
L
L
L
0.024
0.090
L
0.077
0.132
0.112
L
L
0.079
L
L
L
L
0.177
L
L
L
0.070
L
0.041
0.104
L
L
L
L
L
L
L
0.134
L
0.069
0.130
0.129
L
L
L
L
L
L
L

200.5
28.6
17.5
1116.8
804.7
10.6
155.8
48.3
8.9
8.4
15.2
8.6
10.2
1264.5
260.4
13.8
446.7
8.4
24.7
983.1
6.5
51.7
10.9
14.8
16.4
34.0
7.6
10.9
52.4
66.2
94.4
340.1
98.1
2271.6
145.6
9.1
14.8
18.4
9.2
9.4
8.7
10.0
58.9
7.3
52.9
65.9
1297.3345.5±1.7
60±2
15.1±0.93026±32248±39.0±0.9504±3
48.6±1.0
7.8±0.9
7.9±0.9
13.4±0.9
7.7±0.99.7±1.03982±3336.8±1.3
17.2±1.3
713.9±1.67.5±0.9
22.7±0.92731±35.6±0.9
53.3±1.0
11.2±1.0
16.7±1.1
15.6±1.034.6±1.0
6.6±0.99.2±0.8
204±4
63.6±1.0
117.5±1.2
488.9±1.4
117.8±1.213859±6
156.9±1.1
9.4±1.0
15.9±1.1
19.4±1.1
10.3±1.1
10.0±1.19.9±1.1
11.3±1.1
68.2±1.2
8.9±1.2
65.6±1.2
143±25828±4

160.4
31.4
7.6
775.6
507.2
8.5
196.4
41.5
6.0
8.9
14.2
11.8
13.7
796.1
204.6
18.6
298.0
7.6
27.9
685.2
5.4
13.0
8.0
0.0
6.6
27.3
4.9
6.5
74.8
129.5
33.2
264.0
54.0
1398.5
107.4
6.7
6.2
20.7
3.8
5.1
2.8
9.2
29.1
4.2
37.0
47.2
1053.693.1±0.615.2±0.5
1.9±0.3
908±1573±12.0±0.2
129.8±0.713.2±0.3
1.5±0.2
2.4±0.3
3.6±0.3
3.1±0.3
3.9±0.3
1049±1101.6±0.5
6.3±0.3
186.0±0.6
1.9±0.3
7.5±0.3852±11.3±0.2
3.7±0.3
2.3±0.3<0.2
1.8±0.3
8.7±0.3
1.2±0.2
1.5±0.2
47.1±0.650.1±0.412.7±0.4
154.3±0.6
20.6±0.43612±338.9±0.4
2.0±0.3
2.1±0.3
6.2±0.3
1.2±0.3
1.6±0.3
1.0±0.3
2.9±0.3
10.0±0.3
1.4±0.3
13.5±0.424.2±0.52565±2

40.7
11.3
0.0
266.4
238.5
2.2
53.9
9.0
3.1
3.4
5.9
1.9
1.9
420.1
38.6
3.4
140.6
4.2
5.7
227.0
2.3
25.8
0.0
2.9
8.0
6.1
2.6
4.3
37.0
8.7
35.2
52.6
29.7
726.7
36.1
3.3
8.9
4.8
1.2
3.0
2.2
2.1
22.6
0.0
18.8
27.2
466.4

186±552±5<5.41110±41217±56.8±3.2
234±430±310±312±419±36.2±3.2
6.6±3.4
2104±5124±3
12±4551±414±319±3950±47.7±3.3
83±3<7.3
10.5±3.626±320±38.6±3.2
14±3153±428±3132±4
175±398±35485±8118±3
13±433±417±34.8±4.1
12±49.6±4.4
8.3±4.0
93±4<9.3
78±4144±53273±70.08±0.00
0.12±0.03
0.43±0.07
0.03±0.00
0.11±0.00
0.17±0.09
0.11±0.01
0.08±0.02
0.25±0.12
0.02±0.10
0.08±0.06−0.11±0.09−0.12±0.07
0.09±0.00
0.03±0.00−0.07±0.05
0.10±0.00
0.10±0.11−0.02±0.03
0.01±0.00
0.15±0.15
0.64±0.03
0.22±0.09
1.00±0.10
0.46±0.08
0.12±0.03
0.27±0.14
0.32±0.10
0.16±0.02−0.42±0.01
0.49±0.01
0.00±0.00
0.29±0.01
0.10±0.00
0.12±0.01
0.19±0.11
0.42±0.08
0.00±0.04
0.47±0.13
0.34±0.12
0.53±0.16
0.10±0.09
0.37±0.02
0.32±0.15
0.22±0.02
0.31±0.02−0.16±0.00−0.12±0.01
0.12±0.06−0.65±0.06−0.30±0.00−0.11±0.00
0.1±0.3−0.19±0.01−0.05±0.07
0.3±0.3
0.4±0.3
0.34±0.14
0.1±0.3−0.0±0.3−0.13±0.00−0.30±0.01−0.00±0.19
0.06±0.00
0.5±0.2
0.10±0.12−0.32±0.00
0.3±0.4
0.39±0.03−0.37±0.08−0.0±0.2
0.43±0.12−0.09±0.09
0.3±0.3
0.4±0.2
0.05±0.02−0.22±0.06
0.24±0.02−0.31±0.01
0.10±0.02−0.26±0.00
0.05±0.02
0.3±0.3
0.51±0.11
0.11±0.14−0.2±0.4
0.3±0.3
0.2±0.3
0.0±0.3
0.33±0.04−0.13±0.09
0.27±0.04
0.19±0.03−0.10±0.00−0.001±0.000
0.004±0.005−0.01±0.05
0.009±0.001
0.057±0.001−0.05±0.07
0.107±0.001
17.000±0.006
0.16±0.11
13.35±0.02−0.02±0.04−0.03±0.09
0.18±0.07
0.024±0.001
0.135±0.001
14.02±0.01
0.196±0.001
0.11±0.08
10.379±0.008
0.015±0.001−0.23±0.14−0.003±0.004
0.09±0.05
1.44±0.04
13.84±0.01
0.089±0.010
0.14±0.08
0.09±0.06
0.124±0.001
14.905±0.005
0.008±0.002
6.973±0.004
0.079±0.002
0.082±0.003
0.109±0.001
0.07±0.07
0.69±0.06
0.26±0.02
0.14±0.10
0.21±0.05
0.03±0.08
0.05±0.06
7.415±0.005
0.44±0.12
8.259±0.005
0.486±0.003
0.019±0.001

Hori et al.

(1)
No.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Table 4
(Continued)

22

(1)
No.

(2)
3MAXI

(3)
R.A.

(4)
Decl.

(5)
σstata(6)
sD,4 – 10 keV(7)
f4 – 10keV b(8)
sD,3 – 4 keV(9)f3 - 4 keV c(10)
sD,10 – 20 keV(11)f10 – 20keV d

(12)
HR1e

(13)
HR2f

(14)
s 2rms g

189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214

J1959+408
J1959+117
J1959+322
J2008+325
J2015+370
J2022+371
J2032+376
J2032+409
J2037+418
J2052+443
J2056+497
J2103+456
J2123+423
J2124+509
J2128+570
J2134+511
J2136+475
J2142+435
J2143+572
J2207+545
J2228+611
J2235+634
J2245+534
J2253+626
J2323+588
J2346+517

299.848299.860
299.975
302.075
303.996305.510308.041308.097309.409313.074
314.114315.844320.999321.142322.082323.593324.025325.685325.772331.957
337.039338.912341.294343.290
350.855
356.60940.80411.71232.29032.52837.08337.13837.64440.95441.89744.37649.73245.67442.33950.99557.02751.18047.57543.51657.28654.55661.10263.40153.40262.61758.82451.716

L
L
L
L
L
0.089
L
L
L
0.121
L
L
L
L
L
L
L
L
0.149
L
0.159
L
0.120
L
L
L

47.8
279.3
6.9
11.7
15.7
12.6
111.3
779.0
31.4
9.3
13.3
34.8
7.8
42.2
21.4
16.0
8.3
25.1
8.0
66.1
7.6
9.4
9.9
10.0
261.9
9.1

61.4±1.3
401.4±1.4
34±5
14.6±1.218.9±1.2
17.3±1.4
160.3±1.42777±465±2
11.9±1.315.7±1.2
46.4±1.3
9.3±1.2
58.1±1.424.0±1.1
21.3±1.3
10.1±1.230.8±1.2
9.0±1.1
89.3±1.4
7.1±0.98.9±0.9
11.3±1.1
11.8±1.2
387.4±1.5
10.5±1.2

37.2
264.8
12.1
9.1
13.3
15.3
56.8
389.6
25.2
12.2
13.5
21.4
3.1
30.1
17.9
8.7
5.8
19.8
6.4
36.6
4.1
6.4
10.4
19.4
280.5
8.5

14.6±0.4
168.7±0.6
6.0±0.5
3.5±0.4
5.2±0.4
26±225.2±0.4475±1
16.1±0.64.8±0.44.8±0.4
8.7±0.4
1.0±0.3
12.1±0.4
6.1±0.3
3.3±0.4
2.0±0.3
7.2±0.4
2.1±0.3
14.9±0.4
1.2±0.3
1.8±0.3
3.5±0.3
6.0±0.3
206.4±0.7
2.9±0.3

11.4
16.9
1.3
2.6
1.8
0.0
33.4
280.3
1.2
1.9
2.6
11.1
4.7
13.3
4.7
7.3
2.6
6.8
0.0
17.9
0.0
6.3
1.0
1.3
20.9
0.0

50±460±46.8±5.3
12.2±4.78.5±4.7<34.0
153±5
1895±76.6±5.4
9.1±4.8
11.9±4.5
51±521±461±519±434±512.0±4.630±4<7.8
84±5<6.0
22±44.4±4.4
4.7±3.680±4<4.6

0.14±0.02−0.14±0.00
0.29±0.12
0.14±0.08
0.07±0.06−0.64±0.07
0.34±0.01
0.30±0.00
0.12±0.03−0.11±0.08
0.02±0.06
0.26±0.03
0.48±0.16
0.21±0.02
0.11±0.04
0.35±0.07
0.24±0.12
0.15±0.04
0.15±0.12
0.31±0.02
0.32±0.15
0.21±0.11
0.01±0.09−0.23±0.06−0.25±0.00
0.07±0.10

0.09±0.06−0.64±0.01−0.6±0.3
0.1±0.3−0.2±0.3
0.14±0.04
0.17±0.02
0.00±0.00−0.74±0.15
0.1±0.3
0.1±0.2
0.23±0.07
0.5±0.2
0.22±0.06
0.08±0.14
0.40±0.12
0.3±0.3
0.18±0.11−0.25±0.10
0.16±0.04−0.33±0.11
0.57±0.16−0.3±0.5−0.3±0.4−0.54±0.01−0.93±0.15

0.002±0.005
0.118±0.001
0.24±0.01
0.05±0.06
0.08±0.05
0.02±0.05
0.628±0.002
0.122±0.002
0.055±0.006
0.10±0.06
0.11±0.04
1.196±0.006
0.46±0.15
0.009±0.006
0.08±0.02
0.01±0.03
0.03±0.09
0.24±0.02
0.20±0.08
0.205±0.004
0.14±0.08
0.07±0.09
0.15±0.07−0.02±0.05
0.001±0.001
0.11±0.08

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Table 4
(Continued)

Notes.
a
The 1σ statistical position error in units of degrees.
b
The observed 4–10 keV ﬂux in units of 10−12 erg cm−2s−1, converted from Crab units by assuming a Crab-like spectrum; 1 mCrab=1.21×10−11 erg cm−2s−1.
c
The observed 3–4 keV ﬂux in units of 10−12 erg cm−2s−1, converted from Crab units by assuming a Crab-like spectrum; 1 mCrab=3.98×10−12 erg cm−2s−1.
d
The observed 10–20 keV ﬂux in units of 10−12 erg cm−2s−1, converted from Crab units by assuming a Crab-like spectrum; 1 mCrab=8.51×10−12 erg cm−2s−1.
eHR(3–4 keV, 4–10 keV) calculated with Equation (2).
fHR(4–10 keV, 10–20 keV) calculated with Equation (2).
g
Excess variance calculated with Equation (3).

Hori et al.

(1)
No.

(2)
3MAXI

(3)
R.A.

(4)
Decl.

(5)
σstata(6)
sD,4 – 10 keV(7)
f4 – 10keV b(8)
sD,3 – 4 keV(9)f3 – 4keV c(10)
sD,10 – 20 keV(11)f10 – 20keV d

(12)
HR1e

(13)
HR2e

(14)
s 2rms f

215
216
217
218
219
220
221

J0716−196
J0836−432
J1619−382
J1719−284
J1846+007
J1903+031
J2023+336

109.060
129.022244.769259.804
281.560
285.847305.919−19.695−43.223−38.250−28.4100.800
3.162
33.698

0.144
0.016
0.066
0.135
0.077
0.114
0.165

8.0
58.2
12.3
7.9
11.8
10.0
6.6

30±4700±1298±848±670±652±555±8

5.2
24.4
10.5
6.1
5.9
7.6
1.4

5±1
95±427±311±211±214±2
3±2

1.4
27.7
4.2
3.1
2.9
3.6
1.5

20±14958±35
112±26
65±2152±1860±1641±280.28±0.13
0.40±0.02
0.08±0.08
0.15±0.12
0.35±0.10
0.09±0.10
0.7±0.2−0.0±0.4
0.34±0.03
0.25±0.19
0.3±0.3
0.0±0.2
0.3±0.2
0.1±0.4

2.98±0.05
7.99±0.01
11.6±0.1
10.5±0.21.62±0.05
12.8±0.2
11.1±0.4

23Notes.
a
The 1σ statistical position error in units of degrees.
b
The observed 4–10 keV ﬂux in units of 10−12 erg cm−2s−1, converted from Crab units by assuming a Crab-like spectrum; 1 mCrab=1.21×10−11 erg cm−2s−1.
c
The observed 3–4 keV ﬂux in units of 10−12 erg cm−2s−1, converted from Crab units by assuming a Crab-like spectrum; 1 mCrab=3.98×10−12 erg cm−2s−1.
d
The observed 10–20 keV ﬂux in units of 10−12 erg cm−2s−1, converted from Crab units by assuming a Crab-like spectrum; 1 mCrab=8.51×10−12 erg cm−2s−1.
e
HR calculated with Equation (2).
f
Excess variance calculated with Equation (3).
g
The period when these source properties are measured.

(15)
Periodg

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Table 5
Properties of the 73-day Sources in the MAXI/GSC Catalog at ∣b∣ < 10

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Figure 9. (a) The normalized periodograms. The red dotted lines show the level of Poisson ﬂuctuations. The errors refer to the constant variance of 0.31 (Papadakis &Lawrence 1993; Isobe et al. 2015). (b) The normalized periodograms for 73-day sources. The red dotted lines show the level of Poisson ﬂuctuations. The errors refer tothe constant variance of 0.31 (Papadakis & Lawrence 1993; Isobe et al. 2015).

24

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Figure 9. (Continued.)

where f is the frequency of the ﬂux variation, xi is the source
ﬂux at time tj, n is the number of data points, T is the total
duration, and μ is the unweighted average of the source ﬂux. A
frequency range of 5×10−9 Hz to 2×10−8 Hz can beinvestigated from these light curves. Figures 9(a) and (b) show
the normalized periodograms for all objects. We note that theresult of Cyg X-1 is consistent with those obtained in Sugimoto
et al. (2017).

calibration, which was estimated from the variation seen in the
73-day bin light curve of the Crab Nebula.
To quantify the variability of each source, we use the excess
variance (s 2rms) normalized by the square of the mean ﬂux(Vaughan et al. 2003):
s 2rms =1 Nå [(xi - x¯)2 -  2i ] ,Nx¯2 i = 1(3 )where N is the total number of light curve points, x̄ is the meanof the ﬂux, and xi and òi are the ﬂux and its error for each data
point, respectively. The s 2rms value becomes larger in stronger
variability. The error on s 2rms (Ds 2rms) can be calculated via:
Ds 2rms =⎛ 2  2 ⎞2
 2 4s 2rms
,
⎜
⎟ +
2
N x¯2
⎝ N x¯ ⎠4.3. Mean Properties of Each Source Type
Here, we discuss the overall properties of each source type.
Table 8 (3rd to 5th columns) lists the median values of theexcess variance and the means and its standard deviations of
HRs. Galactic sources constitute the largest population (<50%)
in our catalog. As expected, galaxy clusters, (isolated) pulsars,
and supernova remnants show stable light curves, while X-ray
binaries and blazars have large variabilities. Galaxy clusters,stars, and supernova remnants tend to show a softer spectrum.
The majority of high-mass X-ray binaries are X-ray pulsars,
which have a hard spectrum below 20 keV because of nonthermal emission characterized by a hard power-law-like
spectrum (Nagase 1989). Low-mass X-ray binaries show asofter spectrum in the bright state, characterized by blackbody
emission from the surface of a neutron star and multi-color disk
emission (Mitsuda et al. 1984).
The unidentiﬁed and unmatched sources show, on average,
large variability amplitudes (s 2rms ~ 0.1–0.2), which areobserved from blazars, stars, and X-ray binaries in our catalog.
Since their mean HR2 values are ∼−0.1 we infer that the
majority are not high-mass X-ray binaries or stars, which show
mean HR2 values of ∼0.1 and ∼−0.3, respectively. In fact, themean values of HR1 and HR2 of the unidentiﬁed and(4 )where  2 is the mean of the square of òi. These values for eachsource are listed in the 14th Column of Tables 4 and 5.
Periodograms are commonly used to quantify the variabilityof X-ray sources. Employing the same method as Isobe et al.
(2015), we made the periodograms of the individual MAXI
sources from their 73-day bin light curves. We adopted thefollowing formula to estimate the PSD for each source:P( f ) =[a2 ( f ) + b2 ( f )] T,
m2a( f ) =1 n-1
å xj cos (2pftj ) ,n j=0b( f ) =1 n-1
å xj sin (2pftj ) ,
n j=0

(5 )

25

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 9. (Continued.)

26

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 9. (Continued.)27

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 9. (Continued.)

28

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 9. (Continued.)

29

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 9. (Continued.)30

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 9. (Continued.)31

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Figure 9. (Continued.)32

Hori et al.

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Figure 9. (Continued.)

Table 6
Possible Counterparts for the 7-year Sources in the MAXI/GSC Catalog at ∣b∣ < 10
(1)

(2)

(3)

(4)
(5)
Possible Counterpart

(6)

(7)

(8)

(9)

No.

3MAXI

Name

R.A.

Decl.

Δposia

Typeb

Flagc

Noted

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50

J0000+674
J0025+641
J0029+592
J0035+598
J0036+614
J0056+606
J0117+652
J0118+637
J0140+583
J0146+616
J0210+525
J0227+619
J0241+611
J0244+624
J0252+571
J0334+531
J0342+636
J0404+572
J0408+632
J0418+380
J0427+354
J0441+445
J0450+450
J0452+496
J0456+523
J0457+455
J0459+272
J0525+241
J0534+220
J0534+285
J0538+263
J0547+379
J0601+130J0602+285
J0602+230
J0605+299
J0616+225
J0617+091
J0631+251
J0633+049
J0635+225
J0635+077
J0640−127
J0641+098
J0645−169
J0648+152
J0656−035
J0704−114
J0708−155
J0714−254

BD+66 1664
Tycho SNR
V709 Cas
1ES 0033+595
BD +60 73
Gamma Cas
2S 0114+650
4U 0115+634

359.544
6.284
7.204
8.969
9.290
14.17719.511
19.63367.56864.16559.28959.83561.36060.71765.29263.740

0.213
L
L
L
L
L
L
L

Star
SNR
CV
Blazar
HMXB
HMXB
HMXB
HMXB

NR
B
B
B
B
B
B
B

PSR J0146+61
LEDA 138501

26.59332.39361.75152.443

L
L

PulsarSy1

B
B

LS I+61 303[HB89] 0241+622

40.13241.24061.22962.468

L
L

HMXB
Sy1.2

B
B

BQ Cam1RXS J034002.0+635210

53.74955.00853.17363.870

L
0.372

HMXB
unID

B
R

3C 111.0

64.58938.027

L

Sy1.2

B

RX J0440.9+4431
4U 0446+44
1RXS J045205.0+493248

70.24772.43573.02144.53045.04649.546

L
0.050
L

HMXB
Galaxy Cluster
Sy1.5

B
UXM
B

1RXS J045707.4+452751
4C +27.14
1RXS J052523.2+241331
Crab
SWIFT J053457.91+282837.9
1A 0535+262
NVSS J054706+375236

74.28574.98481.34483.63383.74084.72786.77445.46427.10124.22622.01528.47726.31637.874

L
L
L
L
L
L
L

CV
Sy2
CV
Pulsar
unID
HMXB
unID

B
B
B
B
B
B
B

IRAS 05589+2828
RXC J0602.1+2309

90.54590.53128.47323.166

L
0.200

Sy1.2
Galaxy Cluster

B
M

IC 443
4U 0614+091
RXC J0631.3+2500

94.20094.28097.83922.4679.137
25.016

0.117
L
0.162

SNR
LMXB
Galaxy Cluster

XR
B
M

CIZA J0635.0+2231
TYC 733-2098-1
PMN J0640−1253
1RXS J064059.3+095330
V* HL CMa
1RXS J064847.8+151626

98.76498.993100.030
100.247101.322102.19922.5257.922−12.8889.892−16.860
15.274

L
0.166
L
0.172
L
0.012

Galaxy Cluster
Star
BlazarStar
Nova
Blazar

B
N
B
R
B
R

PKS 0706−15
SWIFT J0714.7−2521

107.301108.655−15.450−25.290

L
L

Blazar
unID

B
B

33

T

T
T

T

T

T

T

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Table 6
(Continued)
(1)

(2)

(3)

(4)
(5)
Possible Counterpart

(6)

(7)

(8)

(9)

No.

3MAXI

Name

R.A.

Decl.

Δposia

Typeb

Flagc

Noted

51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112

J0717−114
J0725−064
J0728−206
J0729−262
J0733−135
J0745−162
J0747−192
J0752−442
J0753−459
J0758−221
J0759−387
J0802−496
J0804−276
J0809−406
J0823−430
J0839−358
J0841−562
J0844−378
J0902−481
J0902−405
J0910−526
J0916−623
J0920−552
J0922−632
J1009−582
J1018−582
J1031−621
J1036−568
J1038−497
J1044−596
J1121−606
J1139−653
J1141−639
J1144−698
J1144−610
J1147−619
J1156−566
J1203−538
J1213−648
J1226−627
J1235−646
J1237−667
J1240−577
J1243−630
J1249−590
J1257−692
J1301−615
J1302−639
J1314−602
J1317−629
J1325−577
J1326−621
J1331−549
J1345−623
J1347−606
J1356−645
J1359−633
J1407−618
J1412−653
J1419−610
J1420−626
J1423−541

RXC J0717.4−1119

109.362−11.331

0.154

Galaxy Cluster

M

4U 0728−25
SWIFT J073237.6−133109
1RXS J074616.8−161127
PKS 0745−19

112.223113.156
116.570
116.881−26.108−13.518−16.191−19.294

L
L
L
L

HMXB
CV
CV
Galaxy Cluster

B
B
B
B

RXC J0757.9−2157
2MASS J07594181−3843560
ESO 209- G 012

119.495
119.924120.492−21.962−38.732−49.777

0.170
L
L

Galaxy Cluster
Sy1.2
Sy1.5

M
B
B

4U 0821−42
Fairall 1146

125.826129.628−42.907−35.993

0.153
L

SNR
Sy1.5

UXNR
B

CD-37 5063B
2MASX J09023729−4813339
Vela X-1
SWIFT J0911.3−5229
IRAS 09149−6206
4U 0919−54
V395 CarGRO J1008−57

131.140135.656135.529137.773
139.039140.111140.644152.446−37.963−48.226−40.555−52.547−62.325−55.207−63.295−58.293

0.148
L
L
L
L
L
L
L

Star
Sy1
HMXB
unID
Sy1
LMXB
LMXB
HMXB

NR
B
B
B
B
B
B
B

4U 1036−56
2MASX J10384520−4946531
Eta Carina
Cen X-3
GT Mus
V* V1033 Cen
PKS 1143−696
IGR J11435−6109
1E 1145.1−6141
V* V1040 Cen
LEDA 38038
SWIFT J121314.7−645231
GX 301−2
RT CruXMMSL2 J123629.8-664549
WKK 1263
1H 1249−637
4U 1246−58
4U 1254−690
GX 304−1
2RXP J130159.6−635806
HD 114630B
IGR J13186−6257
RXC J1324.7−5736
4U 1323−619

159.391
159.688
161.265
170.316174.873
175.346
176.473
175.967
176.869
178.863
180.699183.321186.657
188.724
189.125
190.357
190.709
192.414194.405
195.322195.494
198.238199.607201.180
201.650−56.799−49.782−59.684−60.623−65.398−64.172−69.900−61.150−61.954−56.698−53.835−64.880−62.771−64.566−66.764−57.834−63.058−59.087−69.289−61.602−63.968−59.820−62.971−57.614−62.136

L
L
L
L
L
0.209
L
L
L
0.089
L
L
L
L
0.085
L
L
L
L
L
L
0.472
L
0.123
L

HMXB
Sy1.5
Star
HMXB
Star
CV
Blazar
HMXB
HMXB
CV
Sy2
HMXB
LMXB
CV
unID
Sy1.5
HMXB
LMXB
LMXB
HMXB
PulsarStar
HMXB
Galaxy Cluster
LMXB

B
B
B
B
B
N
B
B
B
NR
B
B
B
B
N
B
B
B
B
B
B
NR
B
MNR
B

4U 1344−60
Ginga 1354−644
IGR J14003−6326
MAXI J1409−619
Circinus Galaxy
Rabbit4U 1416−62
RXC J1423.7−5412

206.900
209.550
210.190
212.011213.291214.678215.303215.930−60.618−64.733−63.429−61.983−65.339−60.967−62.698−54.203

L
0.288
L
L
L
L
L
0.038

Sy1.9
LMXB
PulsarPulsarSy2
PulsarHMXB
Galaxy Cluster

B
X
B
B
B
B
B
M

34

T

S
S

T
C

T

T

T

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Table 6
(Continued)
(1)

(2)

(3)

(4)
(5)
Possible Counterpart

(6)

(7)

(8)

(9)

No.

3MAXI

Name

R.A.

Decl.

Δposia

Typeb

Flagc

Noted

113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174

J1442−626
J1446−641
J1449−598
J1453−553
J1455−516
J1502−601
J1509−667
J1513−461
J1514−591
J1520−571
J1533−658
J1542−523
J1547−625
J1548−455
J1548−476
J1551−543
J1601−607
J1612−607
J1617−595
J1629−613
J1640−324
J1641−346
J1650−601
J1650−330
J1653−593
J1655−519
J1702−299
J1709−266
J1710−280
J1712−233
J1713−241
J1730−215
J1731−169
J1738−444
J1741−122
J1750−370
J1803−344
J1806−089
J1807−369
J1810−041
J1814+022
J1823−347
J1823−303
J1825−000
J1828−253
J1829−238
J1834−210
J1836−194
J1839+050
J1849−171
J1855−026
J1855+157
J1858+033
J1858+082
J1901+014
J1904−108
J1904−131
J1910+097
J1910−057
J1910+076
J1911+005
J1911+049

IGR J14471−6414
SWIFT J1448.4−5945
1RXS J145341.1−552146
WKK 4438
SWIFT J1503.7−6028
IGR J15094−6649
RXC J1514.6−4558
PSR B1509−58
Cir X-1

221.617222.179
223.456223.823226.067
227.358
228.651228.481230.170−64.233−59.704−55.362−51.571−60.356−66.823−45.981−59.136−57.167

L
L
L
L
L
L
0.184
L
L

Sy1
HMXB
CV
Sy1.5
unID
CV
Galaxy Cluster
Pulsar
LMXB

B
B
B
B
B
B
MR
B
B

T

H 1538−522
4U 1543−62
NY Lup
4U 1543−47
PSR J1550−5418
1H 1556−605
WKK 6092
WKK 6471

235.597236.976
237.061236.855
237.725240.260
242.964244.652−52.386−62.570−45.478−47.714−54.307−60.738−60.632−59.455

L
L
L
0.252
L
L
L
L

HMXB
LMXB
CV
LMXB
Pulsar
LMXB
Sy1.5
Sy1

B
B
B
UXN
B
B
B
B

IGR J16500−3307
NGC 6221
1RXS J165605.6−520345
XB 1658−298
XTE J1709−267
XTE J1710−281
Oph Cluster
V2400 Oph
Kepler’s SNR
GX 9+94U 1735−44
2E 1739.1−1210
4U 1746−37
1RXS 180408.9−342058

252.482
253.193254.024255.525
257.377
257.552
258.108258.152
262.673262.934264.743265.476
267.553
271.052−33.117−59.217−52.061−29.950−26.656−28.131−23.376−24.246−21.480−16.962−44.450−12.197−37.052−34.313

L
L
L
0.033
L
L
L
L
L
L
L
L
L
0.150

CV
Sy2
Sy1.2
LMXB
LMXB
LMXB
Galaxy Cluster
CV
SNR
LMXB
LMXB
Sy1
LMXB
LMXB

B
B
B
X
B
B
B
B
B
B
B
B
B

SAX J1808.4−3658

272.115−36.979

L

LMXB

B

2E 4061
4U 1820−30
4U 1822−000
MAXI J1828−249
Ginga 1826−24
PKS 1830−21
MAXI J1836−194
Ser X-1

275.910275.919276.342277.243277.367
278.416278.931279.990−34.904−30.361−0.012−25.030−23.791−21.061−19.320
5.036

0.129
L
L
0.325
L
L
L
L

unID
LMXB
LMXB
LMXB
LMXB
Blazar
XRB
LMXB

NR
B
B

XTE J1855−026
2MASX J18560128+1538059
XTE J1858+034
XTE J1859+083
XTE J1901+014

283.877
284.002284.679
284.750285.421−2.60515.632
3.434
8.233
1.438

L
L
L
0.097
L

HMXB
Sy1.2
HMXB
HMXB
HMXB

B
B
B
X
B

4U 1907+09
MAXI J1910−057
4U 1908+075
Aql X-1
SS 433287.408
287.595
287.700
287.817287.957

9.830−5.799
7.596
0.585
4.983

L
L
L
L
L

HMXB
LMXB
HMXB
LMXB
HMXB

B
B
B
B
B

35

T

T

T
T

B
B
B
B

T

T
T

T

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Table 6
(Continued)
(1)

(2)

(3)

(4)
(5)
Possible Counterpart

(6)

(7)

(8)

(9)

No.

3MAXI

Name

R.A.

Decl.

Δposia

Typeb

Flagc

Noted

175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214

J1915+109
J1918−052
J1928+204
J1929+184
J1930+096
J1941+301
J1941+258
J1942+224
J1944+212
J1945+274
J1946+449
J1949+301
J1955+321
J1958+352
J1959+408
J1959+117
J1959+322
J2008+325
J2015+370
J2022+371
J2032+376
J2032+409
J2037+418
J2052+443
J2056+497
J2103+456
J2123+423
J2124+509
J2128+570
J2134+511
J2136+475
J2142+435
J2143+572
J2207+545
J2228+611
J2235+634
J2245+534
J2253+626
J2323+588
J2346+517

GRS 1915+105
4U 1916−053

288.798289.699

10.946−5.238

L
L

LMXB
LMXB

B
B

SWIFT J192955.7+181839
1RXS J193109.5+093714

292.482292.790

18.311
9.621

L
0.103

HMXB
BlazarB
R

HD 344800
SWIFT J1943536.21+211822.9
XTE J1946+275
2MASX J19471938+4449425
KS 1947+300
4U 1954+31
Cyg X-1
Cygnus A
4U 1957+115
SWIFT J2000522.0+320731
SWIFT J2008.8+3225
QSO B2013+370

295.712295.984296.414296.831297.377298.926
299.590299.868
299.851
300.091302.196303.870

22.56321.30627.36544.82830.20732.09735.20240.73411.70932.18932.43037.183

L
L
L
L
L
L
L
L
L
L
L
L

Star
Blazar
HMXB
Sy2
HMXB
LMXB
HMXB
Sy2
LMXB
HMXB
multiple
Blazar

B
B
B
B
B
B
B
B
B
B
B
B

EXO 2030+375
Cyg X-3
SSTSL2 J203705.58+415005.3
4U 2048+44
RX J2056.6+4940
SAX J2103.5+4545
V2069 Cyg
4C 50.55
SWIFT J212745.6+565636
RX J2133.7+5107
2MASX J21355399+4728217
SS CygCep X-4
4U 2206+54

308.063308.107309.273312.589314.178315.899
320.937321.164321.937
323.432
323.975
325.678324.875
331.984

37.63840.95841.83544.56249.66845.75142.30150.97356.94451.12447.47343.58656.98354.519

L
L
L
0.393
L
L
L
L
L
L
L
L
0.573
L

HMXB
HMXB
BlazarLMXBBlazar
HMXB
CV
Sy1.2
Sy1
CV
Sy1.5
CV
HMXB
HMXB

B
B
B
UNR
B
B
B
B
B
B
B
B
X
B

SWIFT J223703.9+632338

339.156

63.492L

unID

B

IGR J22534+6243
Cas A
2MASX J23470479+5142179

343.480
350.850356.770

62.72758.81551.705

L
L
L

unID
SNR
Blazar

B
B
B

T

T
T
T

T
T

Notes.
aAngular separation between the MAXI position and that of possible a counterpart in units of degrees.
b
Sy: Seyfert galaxy, AGN: active galactic nucleus, L(H)MXB: low(high)-mass X-ray binary, XRB: X-ray binary, SNR: supernova remnant, CV: cataclysmic
variable, unID: unidentiﬁed source.
c
Cross-matching ﬂag: B, U, X, N, M, and R indicate that the source has one or more counterparts in the BAT105, 4U, XTEASMLONG, XMMSL2, MCXC, and
1RXS, respectively. The counterpart name listed in column (3) is quoted from the catalog expressed by the leftmost letter in this column.
d
T: Transient or new MAXI source. S: Classiﬁed as an XRB in the original catalog (BAT105). C: Classiﬁed as a symbiotic star in the original catalog (BAT105).

36

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Table 7
Possible Counterparts for the 73-day Source in the MAXI/GSC Catalog at ∣b∣ < 10
(1)

(2)

(3)

(4)
(5)
Possible Counterpart

(6)

(7)

(8)

(9)

No.

3MAXI

Name

R.A.

Decl.

Δposia

Typeb

Flagc

Noted

215
216
217
218
219
220
221

J0716−196
J0836−432
J1619−382
J1719−284
J1846+005
J1903+031
J2023+336

XMMSL2 J071531.3-193957
Ginga 0834−430
MAXI J1619−383
IGR J17191−2821
Ginga 1843+00
4U 1901+03
Ginga 2023+338

108.880
128.979
244.925
259.808
281.403285.905306.016−19.666−43.185−38.375−28.327
0.863
3.192
33.867

0.172
0.050
0.175
0.083
L
0.065
0.187

unID
HMXB
unID
LMXB
HMXB
HMXB
LMXB

N
X
X
B
UX
X

T
T
T

Notes.
aAngular separation between the MAXI position and that of a possible counterpart in units of degree.
b
Sy: Seyfert galaxy, AGN: active galactic nucleus, L(H)MXB: low(high)-mass X-ray binary, XRB: X-ray binary, SNR: supernova remnant, CV: cataclysmic
variable, unID: unidentiﬁed source.
c
Cross-matching ﬂag: B, U, X, N, M, and R indicate that the source has one or more counterparts in the BAT105, 4U, XTEASMLONG, XMMSL2, MCXC, and
1RXS, respectively. The counterpart name listed in column (3) is quoted from the catalog expressed by the leftmost letter in this column.
d
T: Transient or new MAXI source.

approximated by N(>S)∝S−0.5. To evaluate the contributions
from different populations, in Figure 12 we compare the log N–
log S relations of the identiﬁed extragalactic objects (AGNs andgalaxy clusters), LMXBs, and HMXBs, which are the mostdominant ones in our catalog. As noted, the log N–log S slopes
for LMXBs and HMXBs are even ﬂatter than those for 0.5, andthey are consistent with the results by Grimm et al. (2002)
using the RXTE/ASM data at ∣b∣ < 20. In a future work, ourcatalog will be useful to constrain the X-ray luminosity
function of Galactic-disk sources covering low luminosity
ranges down to LX∼1034–35 erg s−1 (assuming a mean
distance of 10 kpc).

unmatched sources are similar to those of blazars or low-mass
X-ray binaries, which are good candidates.
4.4. log N–log S Relation
The log N–log S relation (number counts) represents a basic
statistical property of sources detected in a survey observation.
To derive this relation, we need to create the sensitivity map,
which gives the minimum ﬂux of a source detectable with the
adopted signiﬁcance threshold (sD,4 – 10 keV > 6.5) as a functionof sky position. Following our previous works (Hiroi et al.
2011, 2013), we estimated the sensitivity at each position using
the coverage map (Figure 1) and the background+GRXE map.
Here, we utilized simple analytical formulae that are calibrated
with the actual relations among ﬂux, signiﬁcance, exposure,and background from the cataloged sources. The sensitivity
map enables us to calculate the survey area as a function oflimiting sensitivity (area curve, Figure 10). By dividing theobserved ﬂux distribution of sources by the area curve, thelog N–log S relation in the differential form is obtained, where
the surface number density n(S) dS of sources with ﬂuxes
between S and S+dS is given. In this paper, considering the
low number statistics, we represent it in the integral form
N (>S ) º ò n (S ) dS , i.e., the total surface number density ofSsources with ﬂuxes larger than S.
Figure 11 plots the spatially averaged log N–log S relation in
the 4–10 keV band of the MAXI sources at ∣b∣ < 10 obtained
from the whole survey area (excluding the Galactic center andVela SNR regions). Unlike the case of the high-Galacticlatitude sky, where extragalactic populations are dominant, we
expect large variation of source number density among
different directions at low Galactic latitudes. To demonstrate
this, we also calculated the log N–log S relations from two
separate Galactic longitude regions, (1) l=30°–105° andl=255°–330°, and (2) l=105°–255°, both at ∣b∣ < 10. The
results and corresponding survey area are also plotted in
Figures 10 and 11, respectively.
We ﬁnd that the slope of the log N–log S relation is ﬂatregardless of the Galactic longitude, which can be roughly

5. Conclusion
We have provided the ﬁrst MAXI/GSC source catalog at
low Galactic latitudes, ∣b∣ < 10, outside the Galactic centerregion (∣b∣ < 5, l<30°, and l>330°), based on thedata obtained in 7 years from 2009 August 13 to 2016
July 31. To overcome source confusion in crowded regions,
we have accurately calibrated the PSF of each GSC
camera and improved the background model by utilizing
the onboard data. We have also taken into account thecontribution of the Galactic ridge X-ray emission employing
the model in Revnivtsev et al. (2006). Finally, we havedetected 221 sources with a detection signiﬁcance ofsD,4 – 10 keV > 6.5, 180 of which have 1 or more counterpart(s) after cross-matching with other X-ray catalogs. The
73-day bin light curves over 7 years, and their periodograms
for all the cataloged sources, are presented. To complete
sample information, we are working on the identiﬁcation of
the remaining sources, whose results will be reported infuture papers.
We thank Dr. Kyuseok Oh for sharing the Swift/BAT 105
month catalog with us prior to publication. Part of this work
was ﬁnancially supported by Grants-in-Aid for JSPS Fellows(T.H., T.K.) and for Scientiﬁc Research 17H06362 (Y.U.,
N.K., T.M., H.N., and A.Y.), 16K17672 (M.S.), 16K17667(Y.
37The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

Table 8Mean Properties for Each Source Type
Category
Unidentiﬁed
Blazars
Galaxy Clusters
Seyfert Galaxies
Cataclysmic Variables
Stars
Isolated Pulsars
Supernova RemnantsHigh Mass X-ray Binaries
Low Mass X-ray Binaries
X-ray Binarye
Unmatched

Number of Sourcesas 2rms a,b

HR1a,cHR2a,d

13
12
11
29
17
8
8
5
42
34
1
41

0.126
0.111
−0.018
0.028
0.043
0.116
0.038
0.001
0.205
0.127
10.38
0.119

0.13±0.05
0.04±0.02
0.02±0.03
0.18±0.03
0.27±0.04
0.13±0.07
0.22±0.12−0.32±0.20
0.31±0.03
0.09±0.04−0.02
0.11±0.04−0.13±0.11−0.11±0.11−0.45±0.10
0.12±0.04
0.07±0.10−0.34±0.13
0.05±0.04−0.30±0.17
0.13±0.04−0.09±0.04
0.10−0.06±0.06

Notes.
a73-day sources are included.
b
The median of excess variance calculated by Equation (3).
c
The mean and its standard deviation of HR(3–4 keV, 4–10 keV) calculated by Equation (2).
d
The mean and its standard deviation of HR(4–10 keV, 10–20 keV) calculated by Equation (2).
e
The X-ray binary whose donor star is not ﬁrmly identiﬁed (MAXI J1836–194).

Figure 11. Spatially averaged log N–log S relations in the 4–10 keV band of
the 7-year sources at ∣b∣ < 10 (black: from the whole survey area, red: fromthe l = 30°–105° and l = 255°–330° region, blue: from the l=105°–255°
region). The attached error bars correspond to 1σ.

Figure 10. Survey area as a function of limiting sensitivity in the 4–10 keVband for sD,4 – 10 keV > 6.5 (black: the whole survey area, red: l = 30°–105° andl = 255°–330°, blue: l = 105°–255°).

38

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 March

Hori et al.

S.), and 17K05392(Y.T.) from the Ministry of Education,
Culture, Sports, Science and Technology (MEXT) of Japan. Y.
T. thanks Ryo Sasaki for a useful discussion on stellar X-ray
emission. M.S. acknowledges support by the Special Postdoctoral Researchers Program at RIKEN.

Appendix
PSF Calibration
In Hiroi et al. (2013), the PSF of the GSC was assumed tohave a two-dimensional Gaussian proﬁle in the coordinate
system based on the collimator angle (f and θ; see Sugizaki
et al. 2011, for the deﬁnition) around the original source
positions. However, the actual proﬁle deviates from theGaussian in the direction of the anode wires (i.e., the f axis),
due to the variation in the position where photons are absorbed
in the gas counters, which depends on their incident angles andthe energy of photons. In addition, the ﬁnite slit width makes
the proﬁle broader (see Sugizaki et al. 2011). These effects are
negligible for most X-ray sources compared with their

Figure 12. Spatially averaged log N–log S relations in the 4–10 keV band
obtained from the whole survey area for different populations (black: total,
green: LMXBs, magenta: HMXBs, cyan: extragalactic).

Figure 13. PSF cross-section proﬁles of GSC5 with an anode voltage of 1650 V and their best-ﬁt models along the detector anode-wire direction at (a)f=−32°∼−30°, (b) 4°∼6°, (c) −1.1°∼1°. 0 in 3–4 keV (crosses and red dashed line), 4–10 keV (circles and black solid line), and 10–20 keV (triangles and blue
dotted line).

39

The Astrophysical Journal Supplement Series, 235:7 (40pp), 2018 Marchstatistical errors, but signiﬁcant in brightest Galactic sources,
such as Sco X-1, Crab Nebula, and Cyg X-1.
To measure the actual PSF proﬁle in each camera, wecollected the event data from several brightest isolated sources,
such as Sco X-1, and Crab, and integrated them separately foreach incident angle and energy band. Figures 13(a)–(c) show
the PSF cross-sectional proﬁles obtained from the real event
data, with their best-ﬁt models in the 3–4 keV, 4–10 keV, and10–20 keV bands, along the anode-wire direction for incident
angles (f) of −32° to −30°, 4° to 6°, and −1°. 1 to −1°. 0,
respectively. As noted in Figure 13(a), the PSF shapes at larger
f becomes more asymmetric at higher energies, because
higher-energy photons travel deeper before being absorbed in
the gas counter and the effects of variation in the photonabsorption position become more signiﬁcant. Narrower PSFs
are formed at f∼0° (Figure 13(c)), due to the shielding effectby the support structure of the counter’s beryllium window,
perpendicular to the anode wires. We note that the width of the
PSF proﬁle also depends on the voltage of the anode wires,
1650 or 1550 V.
Considering the results above, we constructed a PSF
database and used it in the simulation for the sources detectedin the image analysis Section 3. The database consists of FITS
ﬁles of PSF data for each camera and each anode voltage (1550
and 1650 V). In these ﬁles the PSF proﬁles along the wire
anodes are tabulated as histograms separately for each f range,
and in energy bands of 3–4 keV, 4–10 keV and 10–20 keV, in aproper format that maxisim can refer to.

Hori et al.

References
Baumgartner, W. H., Tueller, J., Markwardt, C. B., et al. 2013, ApJS, 207, 19
Bird, A. J., Bazzano, A., Bassani, L., et al. 2010, ApJS, 186, 1
Bird, A. J., Bazzano, A., Malizia, A., et al. 2016, ApJS, 223, 15
Bird, A. J., Malizia, A., Bazzano, A., et al. 2007, ApJS, 170, 175
Cash, W. 1979, ApJ, 228, 939
Cooke, B. A., Grifﬁths, R. E., & Pounds, K. A. 1970, in IAU Symp. 37, NonSolar X- and Gamma-Ray Astronomy, ed. L. Gratton (Dordrecht: Reidel), 280
Ebisawa, K., Bourban, G., Bodaghee, A., Mowlavi, N., & Courvoisier, T. J.-L.
2003, A&A, 411, L59
Ebisawa, K., Tsujimoto, M., Paizis, A., et al. 2005, ApJ, 635, 214
Eguchi, S., Hiroi, K., Ueda, Y., et al. 2009, in Proc. of the RIKEN Symp., 44
Forman, W., Jones, C., Cominsky, L., et al. 1978, ApJS, 38, 357
Górski, K. M., Hivon, E., Banday, A. J., et al. 2005, ApJ, 622, 759
Grimm, H.-J., Gilfanov, M., & Sunyaev, R. 2002, A&A, 391, 923
Grindlay, J. E., Hong, J., Zhao, P., et al. 2005, ApJ, 635, 920
Hands, A. D. P., Warwick, R. S., Watson, M. G., & Helfand, D. J. 2004,
MNRAS, 351, 31
Hiroi, K., Ueda, Y., Hayashida, M., et al. 2013, ApJS, 207, 36
Hiroi, K., Ueda, Y., Isobe, N., et al. 2011, PASJ, 63, S677
Islam, N., & Paul, B. 2016, NewA, 47, 81
Isobe, N., Sato, R., Ueda, Y., et al. 2015, ApJ, 798, 27
Matsuoka, M., Kawasaki, K., Ueno, S., et al. 2009, PASJ, 61, 999
Mihara, T., Nakajima, M., Sugizaki, M., et al. 2011, PASJ, 63, S623
Mitsuda, K., Inoue, H., Koyama, K., et al. 1984, PASJ, 36, 741
Nagase, F. 1989, PASJ, 41, 1
Nebot Gómez-Morán, A., Motch, C., Barcons, X., et al. 2013, A&A, 553, A12
Negoro, H., Kohama, M., Serino, M., et al. 2016, PASJ, 68, S1
Oh, K., Koss, M., Markwardt, C. B., et al. 2018, ApJS, 235, 4Papadakis, I. E., & Lawrence, A. 1993, MNRAS, 261, 612
Piffaretti, R., Arnaud, M., Pratt, G. W., Pointecouteau, E., & Melin, J.-B. 2011,
A&A, 534, A109
Revnivtsev, M., Sazonov, S., Gilfanov, M., Churazov, E., & Sunyaev, R. 2006,
A&A, 452, 169
Revnivtsev, M., Sazonov, S., Jahoda, K., & Gilfanov, M. 2004, A&A, 418, 927
Saxton, R. D., Read, A. M., Esquej, P., et al. 2008, A&A, 480, 611
Sugimoto, J., Kitamoto, S., Mihara, T., & Matsuoka, M. 2017, PASJ, 69, 52
Sugizaki, M., Mihara, T., Serino, M., et al. 2011, PASJ, 63, S635
Sugizaki, M., Mitsuda, K., Kaneda, H., et al. 2001, ApJS, 134, 77
Vaughan, S., Edelson, R., Warwick, R. S., & Uttley, P. 2003, MNRAS,
345, 1271
Voges, W., Aschenbach, B., Boller, T., et al. 1999, A&A, 349, 389
Wilson-Hodge, C. A., Cherry, M. L., Case, G. L., et al. 2011, ApJL, 727, L40
Wood, K. S., Meekins, J. F., Yentis, D. J., et al. 1984, ApJS, 56, 507
Yamauchi, S., & Koyama, K. 1993, ApJ, 404, 620

ORCID iDs
T. Hori https://orcid.org/0000-0001-8204-790X
Y. Ueda https://orcid.org/0000-0001-7821-6715
T. Kawamuro https://orcid.org/0000-0002-6808-2052
N. Kawai https://orcid.org/0000-0001-9656-0261
A. Tanimoto https://orcid.org/0000-0002-0114-5581
Y. Sugawara https://orcid.org/0000-0001-6749-1199

40