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Mandatory Fields
Nooraee, N,Callanan, PJ,Barnard, R,Garcia, MR,Murray, SS,Moss, A
Astronomy & Astrophysics
Chandra, Swift, and HST studies of the CXOM31 J004253.1+411422 Very bright X-ray transient in M31
Optional Fields
X-rays: general X-rays: binaries galaxies: groups: individual: M 31 LIGHT CURVES BINARIES NOVAE DISC
Context. A very bright transient X-ray source, CXOM31 J004253.1+411422, was found by Chandra/HRC in the M31 bulge. We present Chandra, Swift, and Hubble Space Telescope (HST) observations of this source.Aims. Since this source is the brightest known X-ray transient in M31, we want to study its nature with Chandra and Swift. Comparing the results of Galactic transients and M31 transients can give a better understanding of the nature of extragalactic binaries.Methods. We fitted disk black body and power law models to X-ray data from Chandra and Swift. Follow-up HST/ACS imaging during and after the outburst revealed a transient optical counterpart.Results. Our HST observations show an optical counterpart with optical magnitude B = 23.91 +/- 0.08. Using the empirical relations between X-ray luminosity and absolute visual magnitude, we estimate the orbital period of the system is about similar to 15 h.Conclusions. Our optical identification of the brightest X-ray transient so far discovered in M31 suggests an orbital period of about 15 h. The decay light curve is consistent with previous models of X-ray novae outbursts.
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