Journal Article

Strong outburst activity of the X-ray pulsar X Persei during 2001–2011

A. Lutovinov, S. Tsygankov and M. Chernyakova

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 423, issue 2, pages 1978-1984
Published in print June 2012 | ISSN: 0035-8711
Published online June 2012 | e-ISSN: 1365-2966 | DOI:
Strong outburst activity of the X-ray pulsar X Persei during 2001–2011

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We present the results of a comprehensive analysis of the X-ray pulsar X Persei over the period 1996–2011, encompassing the quite low state and subsequent strong outburst activity. Using data from the Rossi X-ray Timing Explorer (RXTE) and Swift, we detected several consecutive outbursts, during which the source luminosity increased by a factor of ∼5 up to LX≃ 1.2 × 1035 erg s−1. Previously, the source has been observed in a high state only once. The source spectrum in a standard energy band (4–25 keV) is independent of the flux change and can be described by a model that includes both thermal and non-thermal components. With the help of data from the International Gamma-Ray Astrophysics Laboratory (Integral), we registered the highly significant cyclotron absorption line in the source spectrum and, for the first time, detected a significantly hard X-ray emission from the pulsar up to ∼160 keV. We also report drastic changes of the pulse period during the outburst activity: a long episode of spin-down was changed to spin-up with a rate of yr−1, which is several times higher than previous rates of spin-up and spin-down. To search for a correlation between the X-ray and optical light curves, we took data from the international data base of the American Association of Variable Star Observers (AAVSO). We found no significant correlation between optical and X-ray fluxes at any time-lag from dozens of days to years.

Keywords: pulsars: individual: 4U 0352+309/X Persei; X-ray: binaries

Journal Article.  5582 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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