Discovery of a candidate quiescent low-mass X-ray binary in the globular cluster NGC 6553

Sebastien Guillot, Robert E. Rutledge, Edward F. Brown, George G. Pavlov, Vyacheslav E. Zavlin

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This paper reports the search for quiescent low-mass X-ray binaries (qLMXBs) in the globular cluster (GC) NGC6553 using an XMM-Newton observation designed specifically for that purpose. We spectrally identify one candidate qLMXB in the core of the cluster, based on the consistency of the spectrum with a neutron star H-atmosphere model at the distance of NGC6553. Specifically, the best-fit radius found using the three XMM European Photon Imaging Camera spectra is (for MNS=1.4M®) and the best-fit temperature is . Both physical parameters are in accordance with typical values of previously identified qLMXBs in GC and in the field, i.e., -and -. A power-law (PL) component with a photon index Γ = 2.1+0.5 -0.8 is also required for the spectral fit and contributes 33% of the total flux of the X-ray source. A detailed analysis supports the hypothesis that the PL component originates from nearby sources in the core, unresolved with XMM. The analysis of an archived Chandra observation provides marginal additional support to the stated hypothesis. Finally, a catalog of all the sources detected within the XMM field of view is presented here.

Original languageEnglish (US)
Article number129
JournalAstrophysical Journal
Issue number2
StatePublished - Sep 10 2011

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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