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ROSAT Observations of Soft X-ray Transients in Quiescence

Published online by Cambridge University Press:  25 May 2016

Frank Verbunt
Frank Verbunt*
Affiliation:
Astronomical Institute, Utrecht University, Postbox 80.000, 3508 TA Utrecht, The Netherlands

Abstract

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Four soft X-ray transients, two with a neutron star and two with a black hole, have been detected at quiescence with ROSAT. Blackbody fits to their spectra give temperatures of 160–300 eV, and surface areas of <1 km2. The small surface area suggests that the actual spectrum may be optically thin. The companion star does not contribute significantly to the X-ray luminosity, except perhaps in the case of A 0620-00. From the observation that accretion continues at luminosity levels of ∼1033 erg s−1 it is concluded that the neutron stars in Aql X-1 and Cen X-4 have a weak magnetic field and rotate rather slowly.

Type
5 X-ray Binaries
Information
Symposium - International Astronomical Union , Volume 165: Compact Stars in Binaries , 1996 , pp. 333 - 339
Copyright
Copyright © Kluwer 1996 

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