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Detection of X-Ray Pulsations from the Be/X-Ray Transient A 0535+26 During a Disc Loss Phase of the PrimaryUsing the RossiXTE experiment, we detect weak X-ray emission from the recurrent Be/X-ray transient A 0535+26 at a time when the optical counterpart V725 Tau displayed H.alpha in absorption, indicating the absence of a circumstellar disc. The X-ray radiation is strongly modulated at the 103.5-s pulse period of the neutron star, confirming that it originates from A 0535+26. The source is weaker than in previous quiescence detections by two orders of magnitude and should be in the centrifugal inhibition regime. We show that the X-ray luminosity cannot be due to accretion on to the magnetosphere of the neutron star. Therefore this detection represents a new state of the accreting pulsar. We speculate that the X-ray emission can be due to some matter leaking through the magnetospheric barrier or thermal radiation from the neutron star surface due to crustal heating. The detection of the X-ray source in the inhibition regime implies a reduced density in the outflow from the Be companion during its disc-less phase.
Document ID
20000019652
Acquisition Source
Marshall Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Negueruela, Ignacio
(Nuova Telespazio Rome, Italy)
Reig, Pablo
(Foundation for Research and Technology-Hellas, Iraklion Crete, Greece)
Finger, Mark H.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Roche, Paul
(Leicester Univ. United Kingdom)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Space Radiation
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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