J/MNRAS/443/1821 Supersoft X-ray sources in M31 (Chiosi+, 2014)
Multiwavelength search for counterparts of supersoft X-ray sources in M31.
Chiosi E., Orio M., Bernardini F., Henze M., Jamialahmadi N.
<Mon. Not. R. Astron. Soc., 443, 1821-1836 (2014)>
=2014MNRAS.443.1821C 2014MNRAS.443.1821C
ADC_Keywords: X-ray sources ; Stars, white dwarf ; Photometry, HST
Keywords: binaries: close - white dwarfs - galaxies: individual: M31 -
galaxies: stellar content - ultraviolet: stars - X-rays: stars
Abstract:
We searched for the optical/UV/IR counterparts of seven supersoft
X-ray sources (SSSs) in M31 in the Hubble Space Telescope (HST)
'Panchromatic Hubble Andromeda Treasury' (PHAT) archival images and
photometric catalogue. Three of the SSSs were transient; the other
four are persistent sources. The PHAT offers the opportunity to
identify SSSs hosting very massive white dwarfs (WDs) that may explode
as Type Ia supernovae in single degenerate binaries, with magnitudes
and colour indexes typical of symbiotics, high-mass close binaries, or
systems with an optically luminous accretion disc. We find evidence
that the transient SSSs were classical or recurrent novae; two
probable counterparts that we identified are probably symbiotic
binaries undergoing mass transfer at a very high rate. There is a
candidate accreting WD binary in the error circle of one of the
persistent sources, r3-8. In the spatial error circle of the
best-studied SSS in M31, r2-12, no red giants or AGB stars are
sufficiently luminous in the optical and UV bands to be symbiotic
systems hosting an accreting and hydrogen-burning WD. This SSS has a
known modulation of the X-ray flux with a 217.7s period, and we
measured an upper limit on its derivative, namely |dP/dt|≲0.82x10^11.
This limit can be reconciled with the rotation period of a WD
accreting at a high rate in a binary with an orbital period of a few
hours. However, there is no luminous counterpart with colour indexes
typical of an accretion disc irradiated by a hot central source.
Adopting a semi-empirical relationship, the upper limit for the disc
optical luminosity implies an upper limit of only 169-min for the
orbital period of the WD binary.
Description:
The HST archival data we used comprised the PHAT images and catalogue
(Dalcanton et al., 2012ApJS..200...18D 2012ApJS..200...18D). The PHAT is an HST multicycle
survey of Andromeda, at present in its third year, which at completion
will have imaged one-third of the M31 star-forming disc, covering a
contiguous one square-degree area in 828 orbits with six filters: two
optical ones (F475W and F814W) used with the ACS/WFC camera, two
ultraviolet ones (F275W and F336W) used with the WFC3/UVIS camera, and
two infrared ones (F110W and F160W) used with the WFC3/IR camera.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
target.dat 37 7 X-ray positions of the SSSs (SuperSoft Sources)
table4.dat 71 128 PHAT catalogue coordinates and magnitudes in the
various filters of the objects in the error
circles of six of the SSSs
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Byte-by-byte Description of file: target.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Target Target name
8- 9 I2 h RAh Right ascension (J2000)
11- 12 I2 min RAm Right ascension (J2000)
14- 18 F5.2 s RAs Right ascension (J2000)
20 A1 --- DE- Declination sign (J2000)
21- 22 I2 deg DEd Declination (J2000)
24- 25 I2 arcmin DEm Declination (J2000)
27- 31 F5.2 arcsec DEs Declination (J2000)
33- 37 A5 --- Ctp Counterpart in Hofmann et al.
(2013A&A...555A..65H 2013A&A...555A..65H, Cat. J/A+A/555/A65),
H-NNN, <[HPH2013] NNN> in Simbad
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Target Target name (1)
8- 9 I2 h RAh Right ascension (J2000)
11- 12 I2 min RAm Right ascension (J2000)
14- 18 F5.2 s RAs Right ascension (J2000)
20 A1 --- DE- Declination sign (J2000)
21- 22 I2 deg DEd Declination (J2000)
24- 25 I2 arcmin DEm Declination (J2000)
27- 31 F5.2 arcsec DEs Declination (J2000)
33- 36 F4.2 arcsec Offset [0.1/3] Offset from target
38- 43 F6.3 mag F475W HST/WFC3 F475W magnitude (Vega)
45- 50 F6.3 mag F814W HST/WFC3 F814W magnitude (Vega)
52- 57 F6.3 mag F275W ? HST/WFC3 F275W magnitude (Vega)
59- 64 F6.3 mag F336W ? HST/WFC3 F336W magnitude (Vega)
66- 71 F6.3 mag F110W ? HST/WFC3 F110W magnitude (Vega)
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Note (1): The first row shows the values for the 'blue' candidate in each error
circle, while the rest of the entries are in order of increasing DE.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 16-Apr-2015