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New X-Ray Transient in M31: CXO J004412.4+412548

ATEL # 1016; J.L. Galache, M.R. Garcia, M.A.P. Torres, D. Steeghs, S.S. Murray, F.A. Primini (CfA) and B.F. Williams (U. of Washington)
on 28 Feb 2007; 16:48 UT
Password Certification: Jose Luis Galache (

Subjects: Optical, X-ray, Request for Observations, Binaries, Black Holes, Transients

We report the discovery of a new X-ray source detected in a 5ks observation starting on 2007-02-14.08 UT as part of our ongoing Chandra/HST M31 transient program. The source was detected at coordinates RA(J2000) 00:44:12.4, Dec(J2000) 41:25:48.2, at the edge of the ACIS-S field of view, which results in larger than usual position errors of 2.2" and 2.5", respectively. This location is ~19' from the centre of M31. Modeling the X-ray spectrum with an absorbed disk blackbody, fixing nH = 6.66e20 atoms/cm2 (the Galactic value towards M31), we find Tin ~ 0.63 keV. The luminosity (assuming a distance of 780 kpc to M31) is Lx ~ 9.4e37 erg/s in the 0.5-10 keV range. The presence of a very soft component in the spectrum and the high X-ray luminosity are consistent with the source being a black hole transient in a thermal (high-soft) state. Further optical and X-ray observations of this source are encouraged.

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