Multiple cyclotron features in the spectra of X-ray binary pulsars: the extraordinary case of X0115+63.

A. Santangelo et al.


BeppoSAX observations of the February 1999 outburst of the hard pulsating X-ray transient X0115+63 led to the discovery of four harmonically spaced cyclotron lines in the spectrum of the source, the first ever from a cosmic source. These features, that provide a powerful tool for directly probing the high magnetic field strength which likely characterise the rotating accreting neutron stars of many X-ray binary systems, could give us information on the mechanism and geometry of the accretion processes in the strong gravitational field of neutron star. Here, we report results on the spectral behaviour of the source as a function of the pulse phase, focusing on the phase dependence of the cyclotron features. Presence of multiple cyclotron features in the spectra of other X-ray pulsars observed by BeppoSAX will be discussed and some of the aspects yet to be explored will be highlighted.

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On 16 Jul 1999, 09:18.