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Astron. Astrophys. 345, 576-582 (1999)


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On the nature of the X-ray source 1E 1024.0-5732/Wack 2134

Pablo Reig 1,2,3

1 Physics and Astronomy Department, Southampton University, Southampton, SO17 1BJ, UK
2 Foundation for Research and Technology-Hellas, GR-71110 Heraklion, Crete, Greece
3 Physics Department, University of Crete, GR-71003 Heraklion, Crete, Greece

Received 27 November 1998 / Accepted 1 March 1999

Abstract

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 3 keV 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, [FORMULA] 6.6 keV, than those detected in supergiant HMXB, where a value of 6.4 keV is found, implying that the degree of ionisation of iron is higher in CWB.

Key words: stars: individual: 1 E 1024-5232 = Wack 2134 – stars: Wolf-Rayet – X-rays: stars

Send offprint requests to: pablo@physics.uch.gr

© European Southern Observatory (ESO) 1999

Online publication: April 19, 1999

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