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

F. Haberl, R. Turolla, C.P. de Vries, S. Zane, J. Vink, M. Mendez, F.W.M. Verbunt

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The XMM-Newton spectra of the isolated neutron star RXJ0720.4−3125 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 RXJ0720.4−3125. 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.
Original languageUndefined/Unknown
Pages (from-to)L17-L21
Number of pages5
JournalAstronomy and Astrophysics
Issue number2
Publication statusPublished - 2006

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