Superflares on Giant Stars

Abstract

The Kepler mission identified huge flares on various stars including some of solar type. These events are substantially more energetic than solar flares, and so they are referred to as superflares. Even a small probability of such a superflare on the Sun would be a menace to modern society. A flare comparable in energy with that of superflares was observed on 24th and 25th September on the binary HK Lac. Unlike the Kepler stars, there are observations of differential rotation for HK Lac. This differential rotation appears to be anti-solar. For anti-solar differential rotation, dynamo models can give magnetic activity waves of dipole symmetry as well as quasi-stationary magnetic configurations with quadrupole symmetry. The magnetic energy of such stationary configurations is usually about two orders of magnitude higher than that associated with activity waves. We believe that this mechanism could provide sufficient energy to produce superflares on late type stars, and present some simple models in support of this idea.

arXiv comment7 pages, 3 figures, 1 table. Accepted to Astronomy Reports, 2018, Vol.62, No.8

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Cited by in corpus (5)

• Statistical Properties of Superflares on Solar-type Stars: Results Using All of the Kepler Primary Mission Data
• Active red giants: close binaries versus single rapid rotators
• Superflares on the late-type giant KIC 2852961 -- Scaling effect behind flaring at different energy levels
• Solar and stellar flares: frequency, active regions and stellar dynamo
• Flare Activity and Magnetic Feature Analysis of the Flare Stars II: Sub-Giant Branch