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ATEL # 2730; W. Pietsch (Max-Planck-Institut fuer extraterrestrische Physik, MPE), M. Henze (MPE), F. Haberl (MPE)
on 10 Jul 2010; 19:30 UT
Password Certification: Wolfgang Pietsch (firstname.lastname@example.org)
Subjects: X-ray, Transients
We report the discovery of a new outburst of the recurrent X-ray transient CXOM31J004217.0+411508 (r3-46) in a 4.4 ks Swift XRT observation (ObsID 00035336022) starting on 2010-07-09.95 UT. The source was not yet active in the preceding 3.9 ks observation of the XRT monitoring campaign (00035336021) starting on 2010-07-07.07 UT. We find count rates of 10.6+-1.9 ct/ks and <2.0 ct/ks, respectively, which correspond to luminosities (0.2-10 keV) of 3.5e37 erg/s and <0.7e37 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.
Previous outbursts with similar brightness have been reported for August 2000, October 2001, January 2004, May 2006, and November 2007 (see Henze et al. 2007, ATel #1307 and references therein). Henze et al. proposed a recurrence time of the outbursts of the transient of about 1.2 years. While there was no X-ray coverage at the expected times of outburst in 2003 and 2005, we detected the start of an additional outburst of CXOM31J004217.0+411508 in Chandra HRC-I observations on 2009-02-16.89 UT (ObsID 10683, exposure 19.9 ks) and 2009-02-26.17 UT (10684, 18.7 ks) with count rates of 2.28+-0.47 ct/ks and 6.70+-0.78 ct/ks. Assuming a spectrum as above, these count rates correspond to luminosities (0.2-10 keV) of 0.34e37 erg/s and 1.0e37 erg/s, respectively.
The outbursts in 2009 and 2010 further confirm a recurrence time of the outbursts of about 1.2 years. As already Henze et al mentioned, 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.