A1 Refereed original research article in a scientific journal
Strong outburst activity of the X-ray pulsar X Persei during 2001-2011
Authors: Lutovinov A, Tsygankov S, Chernyakova M
Publication year: 2012
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: Monthly Notices of the Royal Astronomical Society
Volume: 423
Issue: 2
First page : 1978
Last page: 1984
Number of pages: 7
ISSN: 0035-8711
DOI: https://doi.org/10.1111/j.1365-2966.2012.21036.x
Abstract
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 L ≃ 1.2 × 10 ergs . Previously, the source has been observed in a high state only once. The source spectrum in a standard energy band (4-25keV) 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 ∼160keV. 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 , 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. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.
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 L ≃ 1.2 × 10 ergs . Previously, the source has been observed in a high state only once. The source spectrum in a standard energy band (4-25keV) 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 ∼160keV. 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 , 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. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.
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