2013/03/23 by T. F. Cartwright, M. C. Engel, C. O. Heinke +4 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Bulge #Field (mathematics) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Globular cluster #Instability #Luminosity #Luminosity function #Milky Way #astro-ph.HE
paper · pdf · doi:10.1088/0004-637x/768/2/183
17 pages, 7 pages of which are 6 multi-part figures. ApJ, in press
arxiv created 2013/03/23 · openalex publication_date 2013/04/26 · arxiv updated 2015/06/15 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
Ultracompact X-ray binaries (UCXBs) are thought to have relatively simple binary evolution post-contact, leading to clear predictions of their luminosity function. We test these predictions by studying the long-term behavior of known UCXBs in our Galaxy, principally using data from the MAXI All-Sky Survey and the Galactic bulge scans with RXTE 's Proportional Counter Array instrument. Strong luminosity variations are common (and well documented) among persistent UCXBs, which requires an explanation other than the disk instability mechanism. We measure the luminosity function of known UCXBs in the Milky Way, which extends to lower luminosities than some proposed theoretical luminosity functions of UCXBs. The difference between field and globular cluster (GC) X-ray luminosity functions in other galaxies cannot be explained by an increased fraction of UCXBs in GCs. Instead, our measured luminosity function suggests that UCXBs only make up a small fraction of the X-ray binaries above a few × 10 36 erg s −1 in both old field populations and GCs.