Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995mnras.277.1063s&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 277, Issue 3, pp. 1063-1070.
Astronomy and Astrophysics
Astronomy
3
Surveys, Stars: Activity, Stars: Early-Type, Stars: General, Stars: Individual: Alphacar, Radio Continuum: Stars
Scientific paper
A multi-epoch survey with the Parkes telescope of a complete distance-limited sample of 57 stars earlier than F6 has detected possible 8.4-GHz emission from 16 stars. Single-epoch partial synthesis observations with the Australia Telescope Compact Array (ATCA) at 4.8 GHz on 27 stars from the same sample (including the possible Parkes detections) found no emission at the stellar positions above a flux density limit of 1.2-1.9 mJy, but the maps show that the Parkes detections are not merely the results of confusion of sources within the Parkes beam. Three early F stars with UV and/or X-ray emission were observed simultaneously at 4.8 and 8.4 GHz in 12-h syntheses with the 6-element ATCA. Two of these stars were from the above sample and the third was the supergiant Alpha Carinae. We detected only alphaCar with flux densities of 300+/-65 and 140+/-65 muJy at 4.8 and 8.6 GHz (S~nu^-1.3+/-1.3). We discuss the legitimacy of the Parkes 3-6sigma detections and show that, although none has been detected by synthesis observations, there is no compelling reason for rejecting them on the internal evidence. The power emitted by the supergiant alphaCar is similar to that of the 16 possible Parkes detections, although its activity index is orders of magnitude lower. We show that this emission cannot be thermal bremsstrahlung from the 10^7.2-K corona of the star but is probably synchrotron emission from a magnetically maintained corona.
Budding Edwin
Slee Owen Bruce
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