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Detection of a new outburst of the recurrent X-ray transient CXOM31J004217.0+411508

ATel #1307; M. Henze (Max-Planck-Institut fuer extraterrestrische Physik, MPE), W. Pietsch (MPE), F. Haberl (MPE)
on 27 Nov 2007; 17:32 UT
Credential Certification: Wolfgang Pietsch (wnp@mpe.mpg.de)

Subjects: X-ray, Transient

Referred to by ATel #: 1328, 2730

On behalf of the XMM-Newton/Chandra M31 nova monitoring collaboration (see http://www.mpe.mpg.de/~m31novae/xray/ao6/index.php ) we report the discovery of a new outburst of the recurrent X-ray transient CXOM31J004217.0+411508 (r3-46) in a 20ks Chandra HRC-I observation (ObsID 8526) starting on 2007-11-07.64 UT. The source was still active in the following 20ks observation of the HRC-I monitoring campaign (8527) starting on 2007-11-17.76 UT. We find count rates of 12.6+-0.8 ct/s and 9.9+-0.8 ct/s, respectively, which corresponds to a luminosities (0.2-10 keV) of 1.9e37 erg/s and 1.5e37 erg/s (assuming an absorbed power-law model with photon index = 1.7 and NH = 6.6e20 cm-2 at a distance of 780 kpc). The object is identified as a hard source in the 4.55 ks Swift/XRT observation 00031028002, starting on 2007-11-24.21 UT. We find a count rate of 4.8+-1.1 ct/s corresponding to a luminosity of 1.6e37 erg/s, for the same spectral parameters as above, that is consistent with the Chandra luminosities.

The transient was first reported by Kong et al. (2002, ApJ 577, 738). Williams et al. (2006, ApJ 643, 356) give as time of the first outburst 2000-08-18 with a peak luminosity of 3.67e37 erg/s. The X-ray light curve till mid 2002 indicates a second, but not so bright outburst in 2001-10-31 (0.9e37 erg/s, see also Kaaret 2002, ApJ 578, 114). In the Chandra archive, we found two additional outbursts that have not been reported before: ACIS-I, ObsID 4681, 2004-01-31, 2.7e37 erg/s assuming the same spectral parameters; ACIS-I, ObsID 7137, 2006-05-26, 0.7e37 erg/s.

The time lags between the detected outbursts indicate a recurrence time of about 1.2 yr. There is no X-ray coverage at the expected times of outburst in 2003 and 2005. Transients with similar recurrence times have been identified as neutron star systems (e.g. Aql X-1) or black hole systems (e.g. 4U 1630-472) in the Galaxy.

We would like to thank the Swift team for the scheduling of the observations.