Astrophys. J., 609, 735-754 (2004/July-2)
A synoptic X-ray study of M31 with the Chandra high resolution camera.
WILLIAMS B.F., GARCIA M.R., KONG A.K.H., PRIMINI F.A., KING A.R., DI STEFANO R. and MURRAY S.S.
Abstract (from CDS):
We have obtained 17 epochs of Chandra High Resolution Camera (HRC) snapshot images, each covering most of the M31 disk. The data cover a total baseline of ∼2.5 yr and contain a mean effective exposure of 17 ks. We have measured the mean fluxes and long-term light curves for 166 objects detected in these data. At least 25% of the sources show significant variability. The cumulative luminosity function (CLF) of the disk sources is well fitted by a power law with a slope comparable to those observed in typical elliptical galaxies. The CLF of the bulge is a broken power law similar to measurements made by previous surveys. We note several sources in the southwestern disk with LX>1037 ergs/s. We cross-correlate all of our sources with published optical and radio catalogs, as well as new optical data, finding counterpart candidates for 55 sources. In addition, 17 sources are likely X-ray transients. We analyze follow-up Hubble Space Telescope (HST) WFPC2 data of two X-ray transients, finding F336W (U-band equivalent) counterparts. In both cases, the counterparts are variable. In one case, the optical counterpart is transient with F336W=22.3±0.1 mag. The X-ray and optical properties of this object are consistent with a ∼10 M☉ black hole X-ray nova with an orbital period of 23+54–16days. In the other case, the optical counterpart varies between F336W=20.82±0.06 and 21.11±0.02 mag. Ground-based and HST observations show that this object is bright (V=18.8±0.1) and slightly extended. Finally, the frequency of bright X-ray transients in the M31 bulge suggests that the ratio of neutron star to black hole primaries in low-mass X-ray binaries (NS/BH) is ∼1.
Galaxies: Individual: Messier Number: M31 - Galaxies: Spiral - X-Rays: Binaries - X-Rays: Galaxies - X-Rays: General
VizieR on-line data:
<Available at CDS (J/ApJ/609/735): table1.dat table2.dat notes.dat>
Table 2: [KGP2002] r1-NN N=2 added, [KGP2002] r2-NN N=4 added, [KGP2002] r3-NNN N=3 added, [KGP2002] s1-NN N=27 among 85, [KGP2002] s2-NN N=1 (No. 63), [KGP2002] n1-NN N=15 among 85. Table 2: CXOM31 JHHMMSS.s+DDMMSS N=55 added.
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