Further X-Ray Observations of EXO 0748-676 in Quiescence: Evidence for a Cooling Neutron Star Crust

Abstract

In late 2008, the quasi-persistent neutron star X-ray transient and eclipsing binary EXO 0748-676 started a transition from outburst to quiescence, after it had been actively accreting for more than 24 years. In a previous work, we discussed Chandra and Swift observations obtained during the first five months after this transition. Here, we report on further X-ray observations of EXO 0748-676, extending the quiescent monitoring to 1.6 years. Chandra and XMM-Newton data reveal quiescent X-ray spectra composed of a soft, thermal component that is well-fitted by a neutron star atmosphere model. An additional hard powerlaw tail is detected that changes non-monotonically over time, contributing between 4 and 20 percent to the total unabsorbed 0.5-10 keV flux. The combined set of Chandra, XMM-Newton and Swift data reveals that the thermal bolometric luminosity fades from 1-1034 to 6-033, whereas the inferred neutron star effective temperature decreases from 124 to 109 eV.

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Document Details

Document Type
Technical Report
Publication Date
Jul 01, 2010
Accession Number
ADA524183

Entities

People

  • E. F. Brown
  • E. M. Cackett
  • J. Homan
  • James M. L. Miller
  • K. S. Wood
  • M. T. Wolff
  • N. Degenaar
  • P. G. Jonker
  • P. S. Ray
  • W. H. Lewin

Organizations

  • United States Naval Research Laboratory

Tags

Communities of Interest

  • Space

DTIC Thesaurus Topics

  • Artificial Satellites
  • Astrophysics
  • Atmosphere Models
  • Atmospheres
  • Crystal Structure
  • Data Sets
  • Detection
  • Energy
  • Heat Energy
  • Luminosity
  • Models
  • Neutron Stars
  • Observation
  • Observatories
  • Spectra
  • X Ray Spectra
  • X Rays

Fields of Study

  • Physics

Readers

  • Astronomy/Astrophysics
  • Geochemistry
  • Solar Physics

Technology Areas

  • AI & ML