Journal Article

The continued spectral and temporal evolution of RX J0720.4−3125

M. M. Hohle, F. Haberl, J. Vink, C. P. de Vries, R. Turolla, S. Zane and M. Méndez

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 423, issue 2, pages 1194-1199
Published in print June 2012 | ISSN: 0035-8711
Published online June 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.20946.x
The continued spectral and temporal evolution of RX J0720.4−3125

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RX J0720.4−3125 is the most peculiar object among a group of seven isolated X-ray pulsars (the so-called Magnificent Seven), since it shows long-term variations of its spectral and temporal properties on time-scales of years. This behaviour was explained by different authors either by free precession (with a 7 or 14 yr period) or possibly a glitch that occurred around MJD = 528 66 ± 73 d.

We analysed our most recent XMM–Newton and Chandra observations in order to further monitor the behaviour of this neutron star. With the new data sets, the timing behaviour of RX J0720.4−3125 suggests a single (sudden) event (e.g. a glitch) rather than a cyclic pattern as expected by free precession. The spectral parameters changed significantly around the proposed glitch time, but more gradual variations occurred already before the (putative) event. Since MJD ≈ 530 00 d the spectra indicate a very slow cooling by ∼2 eV over 7 yr.

Keywords: stars: neutron; pulsars: individual: RX J0720.4−3125

Journal Article.  3182 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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