Evidence for precession of the isolated neutron star RX J 0720 . 4 − 3125 ⋆
نویسنده
چکیده
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 £t 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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