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[49.03] LMXBs and ULXs in Elliptical Galaxies and Their Relation to Globular Clusters

J. A. Irwin (University of Michigan)

Chandra's surprising discovery that up to 70% of low-mass X-ray binaries (LMXBs) within elliptical galaxies are located within globular clusters has forced us to re-evaluate how LMXBs are formed. The high percentage of LMXB-globular coincidences has lead to the suggestion that all LMXBs are formed in globular clusters, with the present-day field LMXBs having been formed in a globular cluster and subsequently ejected into the field at a later time. In addition, the presence of ultraluminous (>10³⁹ ergs s^-1) X-ray sources (ULXs) within at least two globular clusters of elliptical galaxies poses problems for explaining the formation mechanism of both these sources and their better-known spiral galaxy counterparts with one unified theory. I will review recent Chandra observations of LMXBs and ULXs within elliptical galaxies and discuss correlations between the percentage of LMXBs within globular clusters and the specific frequency of globular clusters in a galaxy. I will also describe efforts to distinguish among LMXB formation mechanisms, specifically whether the field population of LMXBs formed in the field or in globular clusters and were later ejected into the field. Finally, I will compare and contrast elliptical galaxy ULXs and spiral galaxy ULXs.

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Bulletin of the American Astronomical Society, 36 #2
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