The long-term evolution of the accreting millisecond X-ray pulsar Swift J1756.9−2508

Patruno, A., Altamirano, D. and Messenger, C. (2010) The long-term evolution of the accreting millisecond X-ray pulsar Swift J1756.9−2508. Monthly Notices of the Royal Astronomical Society, 403(3), pp. 1426-1432. (doi:10.1111/j.1365-2966.2010.16202.x)

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Abstract

We present a timing analysis of the 2009 outburst of the accreting millisecond X-ray pulsar Swift J1756.9−2508, and a re-analysis of the 2007 outburst. The source shows a short recurrence time of only ∼2 yr between outbursts. Thanks to the approximately 2 yr long baseline of data, we can constrain the magnetic field of the neutron star to be 0.4 × 108≲B≲ 9 × 108 G, which is within the range of typical accreting millisecond pulsars. The 2009 timing analysis allows us to put constraints on the accretion torque: the spin frequency derivative within the outburst has an upper limit of at the 95 per cent confidence level. A study of pulse profiles and their evolution during the outburst is analysed, suggesting a systematic change of shape that depends on the outburst phase. We report also the first evidence that the pulsed fractions increase with energy even if the source is in the hard state.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Messenger, Dr Christopher
Authors: Patruno, A., Altamirano, D., and Messenger, C.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Monthly Notices of the Royal Astronomical Society
Publisher:Wiley-Blackwell Publishing Ltd.
ISSN:0035-8711
ISSN (Online):1365-2966

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