Low-Mass X-ray Binaries and Globular Clusters in Centaurus A

Abstract

We present results of Hubble Space Telescope and Chandra X-ray Observatory observations of globular clusters (GCs) and low-mass X-ray binaries (LMXBs) in the central regions of Centaurus A. Out of 440 GC candidates we find that 41 host X-ray point sources that are most likely LMXBs. We fit King models to our GC candidates in order to measure their structural parameters. We find that GCs that host LMXBs are denser and more compact, and have higher encounter rates and concentrations than the GC population as a whole. We show that the higher concentrations and masses are a consequence of the dependence of LMXB incidence on central density and size plus the general trend for denser GCs to have higher masses and concentrations. We conclude that neither concentration nor mass are fundamental variables in determining the presence of LMXBs in GCs, and that the more fundamental parameters relate to central density and size.

4 pages, 2 figures. Accepted for publication in ApJ Letters

References in corpus (6)

• Formation and evolution of compact binaries in globular clusters: II. Binaries with neutron stars
• Structural parameters for globular clusters in M31 and generalizations for the fundamental plane
• New results on particle acceleration in the Centaurus A jet and counterjet from a deep Chandra observation
• Structural parameters for globular clusters in NGC 5128. III. ACS surface-brightness profiles and model fits
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Cited by in corpus (7)

• Luminosity functions of LMXBs in Centaurus A: globular clusters versus the field
• Where Centaurus A gets its X-ray knottiness
• WFCAM Survey of M31 Globular Clusters: Low Mass X-ray Binaries
• Evidence for Non-Hydrostatic Gas Motions in the Hot ISM of Centaurus A
• A Transient Black-Hole Low-Mass X-Ray Binary Candidate in Centaurus A
• The Distribution of Dark Matter in the Halo of the early-type galaxy NGC 4636
• Globular Clusters and X-ray Point Sources in Centaurus A (NGC 5128)