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.
<Astrophys. J., 610, 247-260 (2004)>
=2004ApJ...610..247D 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
(kTeff≤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. J/ApJ/577/738).
The same region was also observed by Chandra ACIS-S for 37.7ks (after
rejecting high-background periods) on 2001 October 5.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 106 43 VSS source list
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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
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Bytes Format Units Label Explanations
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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 10-3ct/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
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Note (1): Identical sources have the same names in Kong et al. (2002, Cat.
J/ApJ/577/738) and Williams et al. (2004, Cat. J/ApJ/609/735).
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. J/ApJ/577/738) or Williams et al. (2004, Cat. J/ApJ/609/735).
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, 0311374 and
2003ApJ...592..884D 2003ApJ...592..884D.)
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History:
From electronic version of the journal
(End) Marianne Brouty [CDS] 29-Jul-2005