Chandra detection of X-ray transients: a new outburst of RX J0043.2+4127 in M31 GC Bol 163 and Swift J004159.3+410539

ATel #2287; W. Pietsch (Max-Planck-Institut fuer extraterrestrische Physik, MPE), M. Henze (MPE), F. Haberl (MPE) and the XMM-Newton/Chandra M31 nova monitoring collaboration
on 10 Nov 2009; 17:10 UT
Credential Certification: Wolfgang Pietsch (wnp@mpe.mpg.de)

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On behalf of the XMM-Newton/Chandra M31 nova monitoring collaboration (see http://www.mpe.mpg.de/~m31novae/xray/ao8/index.php ) we report the discovery of a new outburst of the recurrent X-ray transient RX J0043.2+4127 = CXO J004317.8+412745 in the M31 globular cluster Bol 163 (see Trudolyubov & Priedorsky 2004, ApJ 616, 821) in a 19.1 ks Chandra HRC-I observation (ObsID 10882) starting on 2009 Nov 07.227 UT. We find a count rate of (6.5+-0.3)x10^-2 ct s^-1 which corresponds to an unabsorbed luminosity (0.2-10 keV) of 1.6x10³⁸ ergs s^-1 (assuming the absorbed power-law model parameters with a photon index of 1.54 and an absorption column density of 1.1x10²¹ cm^-2 given by Trudolyubov & Priedorsky 2004 and a distance of 780 kpc). The transient is in the catalogue of Supper et al. (2001, A&A 373, 63). Trudolyubov & Priedorsky (2004) report an earlier Chandra detection on 2001 Feb 18 and an analysis of ROSAT data that revealed several outbursts.

In the new Chandra observation we also detect the new transient Swift J004159.3+410539 (reported in ATel #2262) with a count rate of (2.4+-0.09)x10^-1 ct s^-1. Assuming the absorbed power-law model parameters with photon index of 1.9 and an absorption column density of 1.4x10²¹ cm^-2 as given in ATel #2262 we derive an unabsorbed luminosity (0.2-10 keV) of 5.5x10³⁸ ergs s^-1 slightly higher than the luminosity derived from the Swift observation (4.6x10³⁸ ergs s^-1, note that the luminosity given in ATel #2262 was too low by a factor of 10). The HRC-I X-ray light curve shows similar variability as in the Swift observation. Again no significant period could be found.