Journal Article

<i>RXTE</i> observation of recent flaring activity from the transient X-ray pulsar 2S 1553−542

Mayukh Pahari and Sabyasachi Pal

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 423, issue 4, pages 3352-3359
Published in print July 2012 | ISSN: 0035-8711
Published online July 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21128.x
RXTE observation of recent flaring activity from the transient X-ray pulsar 2S 1553−542

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We summarize the analysis of observations made by the Rossi X-ray Timing Explorer and the Swift/Burst Alert Telescope at the time of the recent flaring activity of the transient X-ray pulsar 2S 1553−542. The binary system is characterized by the projected semimajor axis ax sin i of 168 ± 18 light-seconds, the binary orbital period Porb of 29.56 ± 0.53 d and the X-ray mass function fx(M) of 5.3 ± 1.2 M. We also found Pspin= 9.2829 ± 0.0003 s with s s−1, i.e. a spin-up rate of yr−1. The spin period is found to decrease more slowly than that of most other X-ray pulsars. As the flare decays with time, the structure and X-ray counts in the pulse profile showed considerable variability. However, no significant structural variability is seen in single-peaked pulse profiles in different energy bands. Pulsed fraction decreases with the decay of the flare but its value at different energy bands showed a discontinuity. Using X-ray spectroscopy at different orbital cycles, we have detected the presence of the Fe Kα emission line in the spectra with a minimum significance of 3σ. Apart from a consistent increase in blackbody temperature, other spectral parameters are found to be stable throughout orbital cycles. From detailed spectral and timing analysis, we concluded that the X-ray flare is spectrally hard and we confirmed the nature of the compact object as a transient, accretion-powered, spin-up X-ray pulsar with a Be-type companion.

Keywords: accretion, accretion discs; stars: emission-line, Be; stars: individual: 2S 1553−542; stars: neutron; X-rays: binaries; X-rays: stars

Journal Article.  4503 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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