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Title: THE SECOND ULTRALUMINOUS X-RAY SOURCE TRANSIENT IN M31: CHANDRA, HUBBLE SPACE TELESCOPE, AND XMM OBSERVATIONS, AND EVIDENCE FOR AN EXTENDED CORONA

XMMU J004243.6+412519 is a transient X-ray source in M31, first discovered 2012 January 15. Different approaches to fitting the brightest follow-up observation gave luminosities 1.3-2.5 Multiplication-Sign 10{sup 39} erg s{sup -1}, making it the second ultraluminous X-ray source (ULX) in M31, with a probable black hole accretor. These different models represent different scenarios for the corona: optically thick and compact, or optically thin and extended. We obtained Chandra ACIS and Hubble Space Telescope Advanced Camera for Surveys observations of this object as part of our transient monitoring program, and also observed it serendipitously in a 120 ks XMM-Newton observation. We identify an optical counterpart at J2000 position 00:42:43.70 +41:25:18.54; its F435W ({approx}B band) magnitude was 25.97 {+-} 0.03 in the 2012 March 7 observation, and >28.4 at the 4{sigma} level during the 2012 September 7 observation, indicating a low-mass donor. We created two alternative light curves, using the different corona scenarios, finding linear decay for the compact corona and exponential decay for the extended corona; linear decay implies a disk that is >5 mag brighter than we observed. We therefore favor the extended corona scenario, but caution that there is no statistical preference for this model in the X-ray spectramore » alone. Using two empirical relations between the X-ray to optical ratio and the orbital period, we estimate a period of {approx}9-30 hr; this period is consistent with that of the first ULX in M31 (18{sup +5}{sub -6} hr)« less
Authors:
; ;  [1]
  1. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
Publication Date:
OSTI Identifier:
22121778
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 772; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLACK HOLES; CAMERAS; LUMINOSITY; STELLAR CORONAE; TELESCOPES; TRANSIENTS; VISIBLE RADIATION; X-RAY SOURCES; X-RAY SPECTRA