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ATEL # 2294; N. Nooraee (Dublin Institute for Advanced Studies, University College Cork), P. Callanan (UCC), M. Garcia (SAO)
on 13 Nov 2009; 17:56 UT
Password Certification: Michael R. Garcia (firstname.lastname@example.org)
Subjects: X-ray, Binaries, Black Holes, Neutron Stars, Transients
Based on a 5ks Chandra ACIS-I observation of M31 on Nov 11 2009, we report a dramatic brightening of CXOM31 J004321.1+411751, [aka r3-7 (Kong et al. 2002 ApJ 577, 738), source 437 (Pietsch, Freyberg, and Haberl 2005 A&A 434, 483), RX J0043.3+4117 (Supper et al. 2001 A&A 373, 63)]. The spectrum on Nov 11 can be well fit with a power law with photon index 2.1 +/- 0.2 and Nh consistent with the Galactic value of 7E20 cm^-2. The observed luminosity over 0.5-10.0 keV assuming a 780 kpc to M31 is 2.6E37 ergs/sec. Observations on Sept 18, Sept 25, and Oct 22 2009 found the source ~20x fainter at luminosity of 1.3E36 ergs/sec, assuming the same spectral shape. This source has previously been known as variable, but the high level of variability found here may suggest an eclipse or a true transient outburst. The average luminosity seen in earlier Chandra observations was 3.7E36 ergs/sec (Kong et al. 2002).