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Optical Constraints on an X-ray Transient Source in M31

Benjamin F. Williams·Michael R. Garcia·Frank A. Primini·Jeffrey E. McClintock·Stephen S. Murray
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Abstract

We have detected a transient X-ray source in the M31 bulge through a continuing monitoring campaign with the Chandra ACIS-I camera. The source was detected at R.A.=00:42:33.428 +/- 0.11'', Dec.=+41:17:03.37 +/- 0.11'' in only a single observation taken 2004 May 23. Fortuitous optical HST/ACS imaging of the transient location prior to the X-ray outburst, along with follow-up HST/ACS imaging during and after the outburst, reveals no transient optical source brighter than B (equivalent) = 25.5. The location of the source and its X-ray properties suggest it is a low mass X-ray binary (LMXB). Assuming the transient is similar to many Galactic X-ray novae, the X-ray luminosity of (3.9 +/- 0.5) X 10$^{37}$ erg s$^{-1}$ and the upper-limit on the optical luminosity provide a prediction of <1.6 days for the orbital period of the binary system.

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Benjamin F. Williams, Michael R. Garcia, Frank A. Primini, Jeffrey E. McClintock, Stephen S. Murray. 2005-06-14. Optical Constraints on an X-ray Transient Source in M31. https://doi.org/10.1086/432597

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