J/ApJ/610/247 M31 supersoft and quasi-soft X-ray sources (Di Stefano+, 2004) ================================================================================ Supersoft X-ray sources in M31. I. A Chandra survey and an extension to quasi-soft sources. Di Stefano R., Kong A.K.H., Greiner J., Primini F.A., Garcia M.R., Barmby P., Massey P., Hodge P.W., Williams B.F., Murray S.S., Curry S., Russo T.A. =2004ApJ...610..247D (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Galaxies, nearby ; X-ray sources Keywords: galaxies: individual (M31) - X-rays: binaries - X-rays: galaxies Abstract: We report on very soft X-ray sources (VSSs) in M31. In a survey that was most sensitive to soft sources in four 8'x8' regions covered by Chandra's ACIS-S S3 CCD, we find 33 VSSs that appear to belong to M31. Fifteen VSSs have spectral characteristics mirroring the supersoft X-ray sources studied in the Magellanic Clouds and Milky Way (kT_eff_<=100eV); we therefore call these "classical" supersoft sources, or simply supersoft sources (SSSs). Eighteen VSSs may have either small (<10%) hard components or slightly higher effective temperatures (but still less than 350eV). We refer to these VSSs as quasi-soft sources (QSSs). Description: The data were taken as part of two separate observing campaigns. One was a survey studying three distinct regions of the disk. These three disk fields, which span a wide range of stellar populations, were each observed three times (15ks for each ACIS-S observation) by Chandra during 2000-2001, at intervals of 3-4months. The second campaign led to superb coverage of the central region. The central region of M31 was observed by Chandra ACIS-I eight times from 1999 to 2001, with exposure times ranging from 4 to 8.8ks. The details of the observations are given in Kong et al. (2002, Cat. ). The same region was also observed by Chandra ACIS-S for 37.7ks (after rejecting high-background periods) on 2001 October 5. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 106 43 VSS source list -------------------------------------------------------------------------------- See also: B/chandra : The Chandra Archive Log (CXC, 2002) J/ApJ/577/738 : M31 Chandra X-ray point sources (Kong+, 2002) J/ApJ/578/114 : Chandra HRC source in M31 (Kaaret, 2002) J/ApJ/609/735 : M31 Chandra X-ray sources (Williams+, 2004) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 6 A6 --- [KGP2002] Object identification (1) 8- 9 I2 h RAh Hour of Right Ascension (J2000) 11- 12 I2 min RAm Minute of Right Ascension (J2000) 14- 17 F4.1 s RAs Second of Right Ascension (J2000) 19 A1 --- DE- Sign of the Declination (J2000) 20- 21 I2 deg DEd Degree of Declination (J2000) 23- 24 I2 arcmin DEm Arcminute of Declination (J2000) 26- 29 F4.1 arcsec DEs Arcsecond of Declination (J2000) 31- 37 F7.2 ct SCts Soft counts (2) 39- 43 F5.2 --- SS/N Soft signal to noise ratio 45- 50 F6.2 ct MCts Medium counts (2) 52- 56 F5.2 --- MS/N Medium signal to noise ratio 58- 62 F5.2 ct HCts Hard counts (2) 64- 67 F4.2 --- HS/N Hard signal to noise ratio 69- 73 F5.2 --- HR1 Hardness ratio 1 (3) 75- 79 F5.2 --- HR2 Hardness ratio 2 (3) 81- 85 F5.2 ct/ks CRate Count rate in units of 10^-3^ct/s 87-101 A15 --- Cat Category (4) 103 A1 --- l_Dist [~] Limit Flag on Dist 104-106 A3 arcsec Dist Angular distance to the nearest X-ray source -------------------------------------------------------------------------------- Note (1): Identical sources have the same names in Kong et al. (2002, Cat. ) and Williams et al. (2004, Cat. ). The prefix r1 designates objects in a square region 2'x2' centered on the nucleus; r2 designates objects outside of r1 but within a square region 8'x8' centered on the nucleus; r3 designates objects outside of r2 but within a square region 23'x23' centered on the nucleus; n1 designates objects outside of r3, north of the nucleus but south of DE=42:01:00 (J2000); n2 designates objects north of DE=42:01:00 (J2000); s1 designates objects outside of r3, south of the nucleus but north of DE=40:31:22 (J2000); s2 designates objects south of DE=40:31:22 (J2000). New objects within these regions are numbered consecutively starting from the highest published number in either Kong et al. (2002, Cat. ) or Williams et al. (2004, Cat. ). The IAU sanctioned names for the sources can be formulated by applying the right ascension and declination to the prefix CXOM31. For example, the proper name of s1-74 is CXOM31 J003956.3+404100. Note (2): The corrected numbers of, respectively, soft, medium and hard X-ray counts detected for each source. Source count rates were determined via aperture photometry and were corrected for effective exposure and vignetting. Note (3): The hardness ratios are defined by: HR1=(M-S)/(M+S) and HR2=(H-S)/(H+S) where S is the soft (0.1-1.1kev) band, M is the medium (1.1-2keV) band, and H is the hard (2-7keV) band. Note (4): Selection criterion by which the source was selected as an SSS. (See Di Stefano & Kong 2003, astro-ph/0311374 and 2003ApJ...592..884D.) -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Marianne Brouty [CDS] 29-Jul-2005