1999A&A...345..576R

Two different models have been put forward to explain the origin of the X-ray emission of the unusual X-ray source 1E 1024.0-5732/Wack 2134: a high-mass X-ray binary system (HMXB) and a colliding wind binary (CWB). We present new optical and X-ray data in an attempt to clarify the nature of this system. The data seem to favour the colliding wind model since the optical spectra show characteristics of both, a Wolf-Rayet and an O-type star, implying that these two type of stars may be present in the system. The lack of coherent modulation (pulsations) and the relatively soft and low luminosity X-ray emission seems to exclude the presence of a neutron star as the body generating the X-ray emission. We present the first X-ray energy spectrum of this source at energies above 3keV and discuss the implications of the spectral parameters obtained from the model fitting. We comment on the fact that the iron lines in CWB are centred at higher energies, ∼6.6keV, than those detected in supergiant HMXB, where a value of 6.4keV is found, implying that the degree of ionisation of iron is higher in CWB.