An unexpected outburst from A0535+262

Abstract

A0535+262 is a transient Be/X-ray binary system which was in a quiescent phase from 1994-2005. In this paper we report on the timing and spectral properties of the INTEGRAL detection of the source in October 2003. The source is detected for ~6000 seconds in the 18-100 keV energy band at a luminosity of ~3.8 x 10^{35} erg s^{-1}; this is compatible with the high end of the range of luminosities expected for quiescent emission. The system is observed to be outside of the centrifugal inhibition regime and pulsations are detected with periodicity, P=103.7 +/- 0.1 seconds. An examination of the pulse history of the source shows that it had been in a constant state of spin-down since it entered the quiescent phase in 1994. The rate of spin-down implies the consistent presence of an accretion disk supplying torques to the pulsar. The observations show that the system is still active and highly variable even in the absence of recent Type I or Type II X-ray outbursts.

5 pages, 4 figures, 1 table. Accepted for publication in MNRAS

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Cited by in corpus (6)

• The Ups & Downs of Accreting X-Ray Pulsars: Decade-long observations with the Fermi Gamma-Ray Burst Monitor
• X-Ray and Optical Observations of A 0535+26
• The pre-outburst flare of the A 0535+26 August/September 2005 outburst
• XMM-Newton observations of 1A 0535+262 in quiescence
• The appearance of magnetospheric instability in flaring activity at the onset of X-ray outbursts in A0535+26
• Catalog of the Galactic population of X-ray pulsars in High-mass X-ray binary systems