The continued spectral and temporal evolution of RX J0720.4−3125
Article first published online: 17 MAY 2012
© 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS
Monthly Notices of the Royal Astronomical Society
Volume 423, Issue 2, pages 1194–1199, June 2012
How to Cite
Hohle, M. M., Haberl, F., Vink, J., de Vries, C. P., Turolla, R., Zane, S. and Méndez, M. (2012), The continued spectral and temporal evolution of RX J0720.4−3125. Monthly Notices of the Royal Astronomical Society, 423: 1194–1199. doi: 10.1111/j.1365-2966.2012.20946.x
- Issue published online: 8 JUN 2012
- Article first published online: 17 MAY 2012
- Accepted 2012 March 16. Received 2012 March 13; in original form 2012 February 24
- stars: neutron;
- pulsars: individual: RX J0720.4−3125
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.