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Evidence for precession of the isolated neutron star RX J0720.4-3125

F. Haberl·R. Turolla·C. P. De Vries·S. Zane·J. Vink·M. Mendez·F. Verbunt
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Abstract

The XMM-Newton spectra of the isolated neutron star RX J0720.4-3125 obtained over 4.5 years can be described by sinusoidal variations in the inferred blackbody temperature, the size of the emitting area and the depth of the absorption line with a period of 7.1 +/- 0.5 years, which we suggest to be the precession period of the neutron star. Precession of a neutron star with two hot spots of different temperature and size, probably not located exactly in antipodal positions, may account for the variations in the X-ray spectra, changes in the pulsed fraction, shape of the light curve and the phase-lag between soft and hard energy bands observed from RX J0720.4-3125. An independent sinusoidal fit to published and new pulse timing residuals from a coherent analysis covering ~12 years yields a consistent period of 7.7 +/- 0.6 years supporting the precession model.

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F. Haberl, R. Turolla, C. P. De Vries, S. Zane, J. Vink, M. Mendez, F. Verbunt. 2006-03-27. Evidence for precession of the isolated neutron star RX J0720.4-3125. https://doi.org/10.1051/0004-6361%3A20065093

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