2012/03/16 by M. M. Hohle, Markus M. Hohle, F. Haberl +8 · 1 citation
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Pulsars and Gravitational Waves Research #astro-ph.HE
paper · pdf · doi:10.1111/j.1365-2966.2012.20946.x
seven pages, three figures, three tables; accepted by MNRAS
arxiv created 2012/03/16 · openalex publication_date 2012/05/17 · arxiv updated 2015/06/04 · openalex created_date 2021/02/01 · openalex updated_date 2026/08/04
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 MJD=52866±73 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 MJD≈53000 days the spectra indicate a very slow cooling by ∼2 eV over 7 years.