2004A&A...423..301T

We present an analysis of archival RXTE and BeppoSAX data of the X-ray source . For the first time, high energy data (≥30keV) are analyzed for this source. The data are well described by comptonization models (CompTT and BMC) in which seed photons with temperatures between 1.1keV and 1.5keV are comptonized by a hot plasma at 50keV thereby producing a hard tail which extends up to, at least, 100keV. We offer a new method of identification of neutron star systems using a temperature - luminosity relation. If a given X-ray source is characterized by a low bolometric luminosity and a relatively high color blackbody temperature (>1keV) it has necessarily to be a neutron star rather than a black hole. From these arguments it is shown that the area of the soft photon source must be small (r≃1km) and that the accretion disk, if present, must be truncated very far from the compact object. Here we report on the possible existence of a cyclotron line around 30keV. The presence of a neutron star in the system is strongly favored by the available data.