A phase-resolved spectroscopic study of the X-ray binary system 4U0115+63 based on Beppo-Sax observations

TL;DR

This study analyzes phase-resolved X-ray spectra of 4U0115+63, revealing phase-dependent cyclotron lines and providing insights into the physical conditions of the source's active regions.

Contribution

It presents the first phase-resolved spectral analysis of 4U0115+63, confirming multiple cyclotron lines and their phase dependence, advancing understanding of neutron star magnetic fields.

Findings

Detection of three strong absorption lines at all phases

Confirmation of a fourth cyclotron line at some phases

Cyclotron features are strongly phase-dependent and non-equidistant

Abstract

We present a phase resolved spectral analysis of the X-ray binary 4U0115+63 based upon Beppo-Sax satellite observations. Three strong absorption lines have been detected at all phases. We interpreted them as a cyclotron resonant scattering. Existence of the fourth cyclotron line has been confirmed at some phases. The cyclotron feature is found to be strongly dependent on the phase of the source, while the continuum part of the spectrum depends on the phase relatively weakly. The cyclotron lines turned out to be very nonequidistant. The second line is almost always deeper then the first one. We discussed physical conditions in the active regions of the source, under which a cyclotron feature similar to the observed one can appear.