XMM-Newton Observations of the Neutron Star X-Ray Transient KS 1731-260 in Quiescence

Rudy Adam Dirk Wijnands, M Guainazzi, M van der Klis, M Méndez

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We report on XMM-Newton observations performed on 2001 September 13-14 of the neutron star X-ray transient KS 1731-260 in quiescence. The source was detected at an unabsorbed 0.5-10 keV flux of only (4-8) x 10(-14) ergs cm(-2) s(-1), depending on the model used to fit the data, which for a distance of 7 kpc implies a 0.5-10 keV X-ray luminosity of approximately (2-5) x 10(32) ergs s(-1). The 2001 September quiescent flux of KS 1731-260 is lower than that observed during the Chandra observation in 2001 March. In the cooling neutron star model for the quiescent X-ray emission of neutron star X-ray transients, this decrease in the quiescent flux implies that the crust of the neutron star in KS 1731-260 cooled down rapidly between the two epochs, indicating that the crust has a high conductivity. Furthermore, enhanced cooling in the neutron star core is also favored by our results.

Original languageEnglish
Pages (from-to)pp.L45-L49.
Number of pages5
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 1 Jul 2002


  • accretion, accretion disks
  • stars : individual (KS 1731-260)
  • X-rays : stars
  • KS-1731-260


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