Are All Low-Mass X-ray Binaries Formed Within Globular Clusters?
Abstract
Recent Chandra observations of nearby early-type galaxies have revealed that a significant fraction (30%--70%) of low-mass X-ray binaries (LMXBs) within these galaxies reside within globular clusters. Yet whether all LMXBs form within globular clusters is still an open question. Using a sample of early-type galaxies observed with Chandra, we address this issue further. For each galaxy, we have determined the total X-ray luminosity, LX, from the sum of the individual LMXBs within each galaxy and compared this value to the number of globular clusters in the galaxy (or more specifically, LX/LB,gal vs. the globular cluster specific frequency, SN). We find a strong correlation between LX/LB,gal and SN, confirming that a significant number of LMXBs are formed within globular clusters. However, the y-intercept of the LX/LB,gal vs. SN relation is not zero, indicating that there is a population of LMXBs that was not formed within globular clusters. We place constraints on the relative importance of the non-globular cluster LMXB population and discuss the implications of our result.
- Publication:
-
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 2003
- Bibcode:
- 2003AAS...203.5201I