Colloquium on 11 February 2016
Flare stars across the H-R diagram


Title: Flare stars across the H-R diagram
Speaker: Luis Balona
Date: Thursday, 11 February 2016
Time: 11:00 - 12:00
Venue: SAAO Auditorium


Stars cooler than F5 have convective envelopes. Such stars develop surface magnetic fields due to dynamo action. This, in turn, allows starspots to develop and re-connection of magnetic field lines releases energy in the form of flares. On the other hand, stars hotter than F5 have radiative envelopes and magnetic fields are thought to be absent. Such stars do not have starspots nor flares. While this is our current understanding, high-precision photometric observations of A and B stars from the Kepler satellite show light variations which are most easily interpreted as starspots. Furthermore, flares are seen in many A stars. These flares cannot be attributed to a proposed cool companion. In this talk I present a summary of our current view of magnetic fields, spots and flares on stars and demonstrate that this view needs to be modified. Furthermore, I argue that far from being an attribute of mostly K and M stars, flare stars are a common property of all stars across the H-R diagram.

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