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Astron. Astrophys. 354, 551-556 (2000)

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A search for nonthermal radio emission from OB and WR stars with RATAN-600

Natalya V. Raguzova and Valerii N. Sidorenkov

Sternberg Astronomical Institute, Moscow University, Moscow, 119899 Russia

Received 4 June 1999 / Accepted 7 December 1999

Abstract

We have searched for nonthermal radio emission from 40 OB and WR stars. Enhanced nonthermal radio emission from an early-type star could be evidence for the presence of a collapsed companion, and thus for its origin as the result of a supernova explosion in a massive binary. As shown in the evolutionary calculations of joint evolution of a neutron star and a normal star in binaries (Lipunov & Prokhorov 1987), a considerable fraction of neutron stars in binary systems having an optical companion must be in the ejector state. A neutron star in this state generates a relativistic wind like an isolated radio pulsar. Most ejectors in binary systems can not be identified as radio pulsars because of absorption of radiowaves in the stellar wind of the normal companion, but instead, they may appear as sources of high-energy quanta due to the synchrotron radiation of relativistic particles (ejected by the radio pulsar) in the magnetic field of a normal star (Lipunov & Prokhorov 1984; Lipunov & Nazin 1994). In this case a source of nonthermal radiation in a wide range from radio to hard gamma-ray may appear as a result of a specific reflection effect in the magnetic field of the optical companion. Cyg X-3 and the periodic radioburster LS I [FORMULA] may be examples of just this kind. To test this idea, measurements of radio flux densities in the range from 0.96 to 21.7 GHz from selected OB and WR stars were made with the RATAN-600. No nonthermal radio emission from the selected stars were detected.

Key words: stars: early-type – stars: Wolf-Rayet – stars: binaries: close – radio continuum: stars – radiation mechanisms: non-thermal

Send offprint requests to: N.Raguzova

Correspondence to: raguzova@sai.msu.su

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© European Southern Observatory (ESO) 2000

Online publication: February 9, 2000
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