Mass loss rate determination of southern OB stars

¹ Instituto Argentino de Radioastronomía, C.C.5, (1894) Villa Elisa, Buenos Aires, Argentina
² Fac. de Cs. Astronómicas y Geofísicas, La Plata National University, Paseo del Bosque S/N, (1900) La Plata, Argentina
³ Australia Telescope National Facility, CSIRO, PO Box 76, Epping, NSW 1710, Australia

Corresponding author: P. Benaglia, paula@irma.iar.unlp.edu.ar

Received: 1 March 2001
Accepted: 23 April 2001

Abstract

A sample of OB stars (eleven Of, one O and one B supergiant) has been surveyed with the Australia Telescope Compact Array at 4.8 and 8.64 GHz with a resolution of ~2´´-4´´. Five stars were detected; three of them have negative spectral indices, consistent with non-thermal emission, and two have positive indices. The thermal radiation from HD 150135 and HD 163181 can be explained as coming from an optically thick ionized stellar wind. The non-thermal radiation from CD-47° 4551, HD 124314 and HD 150136 possibly comes from strong shocks in the wind itself and/or in the wind colliding region if the stars have a massive early-type companion. The percentage of non-thermal emitters among detected O stars has increased up to ~50% . The Of star HD 124314 clearly shows flux density variations. Mass loss rates (or upper limits) were derived for all the observed stars and the results compared with non-radio measurements and theoretical predictions.