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Flare stars across the H-R diagram: a clue to the origin of the corona

Published online by Cambridge University Press:  09 September 2016

L. A. Balona
L. A. Balona*
Affiliation:
South African Astronomical Observatory, P.O. Box 9, Observatory 7935, Cape Town, South Africa email: [email protected]
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Abstract

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Kepler observations show that starspots and superflares are present in A stars. An analysis of Kepler short-cadence data shows that the relative number of A/F flare stars is only a factor of four smaller than K/M flare stars, which can be explained as a selection effect. The average maximum flare amplitude does not depend much on spectral type, which is to be expected if the size of the active region scales in proportion to the stellar radius. The presence of starspots and superflares in A stars suggests that these stars have magnetic fields. However, X-ray observations show that A stars do not possess coronae. I therefore conclude that convection in the stellar envelope is a necessary condition for the formation of the corona. A magnetic field may be necessary to enable coronal heating.

Keywords

stars: flarestars: coronaestars: spots
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , Symposium S320: Solar and Stellar Flares and their Effects on Planets , August 2015 , pp. 249 - 258
Copyright
Copyright © International Astronomical Union 2016 

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