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arXiv · 1203.3708

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

Markus M. Hohle·Frank Haberl·Jacco Vink·Cor P. de Vries·Roberto Turolla·Silvia Zane·Mariano Méndez
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Abstract

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 seven or fourteen years period) or possibly a glitch that occurred around $\mathrm{MJD=52866\pm73 days}$. 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 $\mathrm{MJD\approx53000 days}$ the spectra indicate a very slow cooling by $\sim$2 eV over 7 years.

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Markus M. Hohle, Frank Haberl, Jacco Vink, Cor P. de Vries, Roberto Turolla, Silvia Zane, Mariano Méndez. 2012-03-16. The continued spectral and temporal evolution of RX J0720.4-3125. https://doi.org/10.1111/j.1365-2966.2012.20946.x

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