skip to main content

Title: Faint X-ray binaries and their optical counterparts in M31

X-ray binaries (XRBs) are probes of both star formation and stellar mass, but more importantly remain one of the only direct tracers of the compact object population. To investigate the XRB population in M31, we utilized all 121 publicly available observations of M31 totalling over 1 Ms from Chandra's ACIS instrument. We studied 83 star clusters in the bulge using the year 1 star cluster catalogue from the Panchromatic Hubble Andromeda Treasury Survey. We found 15 unique star clusters that matched to 17 X-ray point sources within 1'' (3.8 pc). This population is composed predominantly of globular cluster low-mass XRBs, with one previously unidentified star cluster X-ray source. Star clusters that were brighter and more compact preferentially hosted an X-ray source. Specifically, logistic regression showed that the F475W magnitude was the most important predictor followed by the effective radius, while color (F475W–F814W) was not statistically significant. We also completed a matching analysis of 1566 H II regions and found 10 unique matches to 9 X-ray point sources within 3'' (11 pc). The H II regions hosting X-ray point sources were on average more compact than unmatched H II regions, but logistic regression concluded that neither the radius nor Hα luminositymore » was a significant predictor. Four matches have no previous classification and thus are high-mass XRB candidates. A stacking analysis of both star clusters and H II regions resulted in non-detections, giving typical upper limits of ≈10{sup 32} erg s{sup –1}, which probes the quiescent XRB regime.« less
Authors:
; ;  [1]
  1. Department of Physics and Astronomy, Western University, London, ON, N6A 3K7 (Canada)
Publication Date:
OSTI Identifier:
22365481
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 790; 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; BINARY STARS; CATALOGS; CLASSIFICATION; COLOR; DETECTION; LUMINOSITY; MASS; STAR CLUSTERS; STAR EVOLUTION; STARS; X RADIATION; X-RAY GALAXIES; X-RAY SOURCES