Journal Article

The 2009 outburst of accreting millisecond pulsar IGR J17511–3057 as observed by <i>Swift</i> and <i>RXTE</i>

Askar Ibragimov, Jari J. E. Kajava and Juri Poutanen

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 415, issue 2, pages 1864-1874
Published in print August 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18836.x
The 2009 outburst of accreting millisecond pulsar IGR J17511–3057 as observed by Swift and RXTE

Show Summary Details

Preview

The twelfth accretion-powered millisecond pulsar, IGR J17511–3057, was discovered in 2009 September. In this work we study its spectral and timing properties during the 2009 outburst based on Swift and RXTE data. Our spectral analysis of the source indicates only slight spectral shape evolution during the entire outburst. The equivalent width of the iron line and the apparent area of the blackbody emission associated with the hotspot at the stellar surface both decrease significantly during the outburst. This is consistent with a gradual receding of the accretion disc as the accretion rate drops. The pulse-profile analysis shows absence of dramatic shape evolution with a moderate decrease in pulse amplitude. This behaviour might result from a movement of the accretion-column footprint towards the magnetic pole as the disc retreats. The time lag between the soft and the hard energy pulses increase by a factor of 2 during the outburst. A physical displacement of the centroid of the accretion shock relative to the blackbody spot or changes in the emissivity pattern of the Comptonization component related to the variations of the accretion-column structure could cause this evolution. We have found that IGR J17511–3057 demonstrates outburst stages similar to those seen in SAX J1808.4–3658. A transition from the ‘slow decay’ into the ‘rapid-drop’ stage, associated with the dramatic flux decrease, is also accompanied by a pulse phase shift which could result from an appearance of the secondary spot due to the increasing inner disc radius.

Keywords: accretion, accretion discs; methods: data analysis; pulsars: individual: IGR J17511–3057; X-rays: binaries

Journal Article.  7664 words.  Illustrated.

Subjects: Astronomy and Astrophysics

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.