EDP Sciences
Free Access
Volume 415, Number 2, February IV 2004
Page(s) L31 - L34
Section Letters
DOI https://doi.org/10.1051/0004-6361:20040009

A&A 415, L31-L34 (2004)
DOI: 10.1051/0004-6361:20040009


Long-term variability in the X-ray emission of RX J0720.4-3125

C. P. de Vries1, J. Vink1, M. Méndez1 and F. Verbunt2

1  SRON, National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
2  Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands

(Received 28 December 2003 / Accepted 14 January 2004)

We detect a gradual, long-term change in the shape of the X-ray spectrum of the isolated neutron star RX J0720.4-3125, such that the spectrum of the source can no longer be described as a blackbody spectrum. The change is accompanied by an energy-dependent change in the pulse profile. If the X-ray emission is influenced by the magnetic field of the pulsar, these changes in spectral shape may point to precession of the neutron star.

Key words: neutron stars -- X-rays

Offprint request: C.P. de Vries, C.Pde.Vries@sron.nl

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