We present an analysis of archival RXTE and BeppoSAX data of the X-ray source
4U2206+54 . For the first time, high energy data (> 30 kev) are analyzed for
this source. The data are well described by comptonization models (CompTT and
BMC) in which seed photons with temperatures between 1.1 kev and 1.5 kev are
comptonized by a hot plasma at 50 kev thereby producing a hard tail which
extends up to, at least, 100 kev. 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 (>1 kev) 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 ~ 1 km) 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 30 kev. The presence of a
neutron star in the system is strongly favored by the available data.Comment: Accepted for publication in A&A. 9 pages, 7 figures. Submitted to
journal in November 200
