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Description
The authors monitored the Cassiopeia dwarf galaxy (IC 10) in a series of 10 Chandra ACIS-S observations to capture its variable and transient X-ray source population, which is expected to be dominated by High Mass X-ray Binaries (HMXBs). They present a sample of 21 X-ray sources that are variable between observations at the 3-sigma level, from a catalog of 110 unique point sources (the HEASARC notes that there are actually 111 sources in the CDS version of the catalog from which this HEASARC table originates). The authors find four transients (flux variability ratio greater than 10) and a further eight objects with ratios >5. The observations span the years 2003-2010 and reach a limiting luminosity of >10<sup>35</sup> erg/s, providing sensitivity to X-ray binaries in IC 10 as well as flare stars in the foreground Milky Way. The nature of the variable sources is investigated from light curves, X-ray spectra, energy quantiles, and optical counterparts. The purpose of this study is to discover the composition of the X-ray binary population in a young starburst environment. IC 10 provides a sharp contrast in stellar population age (<10 million years) when compared to the Magellanic Clouds (40-200 Myr) where most of the known HMXBs reside. The authors find 10 strong HMXB candidates, 2 probable background active galactic nuclei, 4 foreground flare-stars or active binaries, and 5 not yet classifiable sources. Complete classification of the sample requires optical spectroscopy for radial velocity analysis and deeper X-ray observations to obtain higher S/N spectra and search for pulsations. A catalog (contained in this HEASARC table) has been created and supporting data sets (the data used to create the light curves shown in Figures 3, 4 and 5 in the reference paper) are available at <a href="http://cdsarc.u-strasbg.fr/ftp/cats/J/ApJ/836/50/">http://cdsarc.u-strasbg.fr/ftp/cats/J/ApJ/836/50/</a>. A monitoring series of 7x15 ks Chandra/ACIS observations, spaced at roughly six-week intervals was obtained during 2009-2010. A pair of very deep ACIS-S3 observations (2x45ks) made in 2006 November provided a reference data set for improved source positions and spectral information. The original Wang+ (2005, MNRAS, 362, 1065) Chandra (ACIS-S3) observation of 30 ks made in 2003 was also included in this analysis. The complete listing of 10 Chandra observation identifiers (ObsIDs) comprising the data set is summarized in Table 1 of the reference paper, also shown here: <pre> MJD |Date |ObsID|Flag|Exp.|RA(J2000)Dec(J2000)|Roll|Num. Sources ks hh mm ss dd mm ss deg. 52710.7|2003 Mar 12 |03953|a |28.9|00 20 25 +59 16 55|339.27|31 54041.8|2006 Nov 2 |07082| |40.1|00 20 04 +59 16 45|223.70|48 54044.2|2006 Nov 5 |08458| |40.5|00 20 04 +59 16 45|223.70|41 55140.7|2009 Nov 5 |11080| |14.6|00 20 17 +59 17 56|226.53|19 55190.2|2009 Dec 25 |11081| | 8.1|00 20 19 +59 18 02|286.15|24 55238.5|2010 Feb 11 |11082| |14.7|00 20 23 +59 17 10|320.56|24 55290.6|2010 Apr 4 |11083| |14.7|00 20 34 +59 19 01| 10.32|25 55337.8|2010 May 21 |11084| |14.2|00 20 25 +59 20 16| 67.89|27 55397.5|2010 Jul 20 |11085| |14.5|00 20 11 +59 19 13|121.25|22 55444.6|2010 Sep 5 |11086| |14.7|00 20 15 +59 18 11|157.71|27 |2006 Nov 2-5 |57082|b |80.6|00 20 04 +59 16 45|223.70|63 </pre> Flag values as follows: <pre> a = ObsID 03953 used about half of the CCD area in subarray mode. b = Merged 2006 data set referred to as ObsID 57082 consists of the nearly contiguous ObsIDs 07082 and 08458, which had identical pointings. </pre> Roll is the spacecraft roll angle, and Num. Sources is the number of unique point sources detected in each observation after combining wavdetect lists from the soft (S: 0.3-1.5 keV), broad (B: 0.3-8 keV) and hard (H: 2.5-8 keV) energy bands. This table was created by the HEASARC in November 2017 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/836/50">CDS Catalog J/ApJ/836/50</a> file table2.dat. This is a service provided by NASA HEASARC .
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