The XLF of LMXBs in the fields of early-type galaxies, their metal-rich, and metal-poor globular clusters
Abstract
The X-ray luminosity function (XLF) of extragalactic low mass X-ray binaries (LMXBs) can provide insights into their nature and origin. We present an analysis of seven early-type galaxies. These galaxies have deep Chandra observations, which detect X-ray sources down to 1037erg/s, and HST optical mosaics that enable the classification of these sources into field LMXBs, globular cluster (GC) LMXBs, and contaminating sources. At all luminosities, we find that the number of field LMXBs per stellar mass is similar in these galaxies. This sample therefore suggests that the GC specific frequency may not influence the field LMXB population. It also suggests that other parameters, such as the stellar IMF, are either similar across the galaxy sample or vary in a way that does not effect the LMXB population. The XLF of the field and GC LMXBs are significantly different (p-value of 3x10-6), with the latter having a flatter XLF. The XLFs of the metal-rich and metal-poor GC LMXBs are similar, although larger samples will be needed to provide sharper tests in the future.
- Publication:
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AAS/High Energy Astrophysics Division #15
- Pub Date:
- April 2016
- Bibcode:
- 2016HEAD...1512019P