Discovery of an X-ray Nova in M31

Abstract

We have obtained snapshot images of an X-ray nova in M31 from Chandra ACIS-I and the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS). The Chandra position of the X-ray nova was R.A.=00:44:06.68 +/- 1.74", Dec.=+41:12:20.0 +/- 2.31". A follow-up HST observation 24 days later revealed a source at R.A.=00:44:06.81, Dec.=+41:12:24.0 that was B=25.75 +/- 0.05. This optical source faded to B=27.1 +/- 0.1 in 3 months. During this time period, the X-ray flux decayed linearly from (3.6 +/- 0.2) X 10^{-4} to <(6.9 +/- 0.09) X 10^{-5} ct cm^{-2} s^{-1}. The HST identification of an optical source in the same region experiencing an obvious drop in brightness in concert with the X-ray nova suggests that this optical source is the counterpart of the X-ray nova. However, the precision of the X-ray position allows the possibility that the optical source is a nearby variable star. We discuss the implications of both possibilities.

arXiv comment20 pages, 3 figures, 5 tables, accepted for publication in ApJ

References in corpus (9)

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Cited by in corpus (9)

• The deep XMM-Newton Survey of M 31
• A Catalog of Transient X-ray Sources in M31
• Time variability of X-ray sources in the M 31 centre field
• High-Resolution Mapping of Dust via Extinction in the M31 Bulge
• Chandra and Hubble Study of a New Transient X-ray Source in M31
• An X-ray Transient and Optical Counterpart in the M31 Bulge
• A Soft X-ray Transient in the M31 Bulge
• Optical Constraints on an X-ray Transient Source in M31
• Variable Star Candidates in an ACS Field of M31