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Astron. Astrophys. 332, 251-267 (1998)


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Radio observations of stellar winds from early type stars * **

S. Scuderi 1, N. Panagia 2, 3, C. Stanghellini 4, C. Trigilio 4 and G. Umana 4

1 Osservatorio Astrofisico di Catania, Viale Andrea Doria 6, I-95125 Catania, Italy (e-mail: scuderi@ct.astro.it)
2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA (e-mail: panagia@stsci.edu)
3 Affiliated to the Astrophysics Division, Space Science Department of ESA
4 Istituto di Radioastronomia del CNR, Stazione VLBI di Noto, C.P. 141, I-96017 Noto, Italy
(e-mail: carlo@ira.noto.cnr.it, umana@ira.noto.cnr.it, trigilio@ira.noto.cnr.it)

Received 20 May 1997 / Accepted 18 November 1997

Abstract

Fifteen O and B supergiants have been observed with the Very Large Array (VLA) at 4.85, 8.45, and 14.95 GHz in order to make a detailed comparative study of the mass loss rates evaluated from H [FORMULA] and radio continuum observations and reveal and quantify possible departures from standard wind conditions. We detected 12 sources, 7 of which for the first time, thus increasing by 30% the total number of detections of OB supergiants in the northern sky. Radio spectral slopes indicate that the radio emission is mainly of thermal origin in all objects with one exception (HD 190603) out of the 12 detections. Our results demonstrate the value of using H [FORMULA] for mass loss rate determinations, especially for stars that are too distant or too faint to be detected with radio techniques. The relationship [FORMULA] for supergiants turns out to be appreciably flatter than commonly reported, i.e. [FORMULA].

Key words: stars: early-type – stars: mass loss – stars: supergiants – radio continuum: stars

* Based on observations with the Very Large Array. The VLA is a facility of the National Radio Astronomy Observatory which is operated by the Associated Universities Inc. under cooperative agreement with the National Science Foundation.
** This research has made use of the Simbad database, operated at CDS, Strasbourg, France

© European Southern Observatory (ESO) 1998

Online publication: March 10, 1998
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