Strong outburst activity of the X-ray pulsar X Persei during 2001-2011
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 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- June 2012
- DOI:
- 10.1111/j.1365-2966.2012.21036.x
- arXiv:
- arXiv:1204.0483
- Bibcode:
- 2012MNRAS.423.1978L
- Keywords:
-
- pulsars: individual: 4U 0352+309/X Persei;
- X-ray: binaries;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 8 pages, 6 figures, accepted for publication in MNRAS