Untersuchung der Superflare-Aktivität bei sonnenartigen Sternen

Kitze, Manfred GND

During the last centuries historic observations revealed the magnetic activity of the sun. The large-scaled poloidal magnetic field reverses during a cycle of about 11 years. Especially during the maximum of particular cycles, dark sunspots can occur on the solar surface, which can store a huge amount of magnetic energy. If magnetic reconnection happens in the solar atmosphere, strong explosions and eruptions of material can be generated, which are called Flares. It is of special interest to study numerous stars with properties similar to the sun to draw meaningful statistics on flares in high energy ranges. In previous studies the first 120 d and 500 d of Kepler-data have been investigated (Maehara u. a., 2012; Shibayama u. a., 2013). It could be shown, that sun-like stars are able to create flares which are one to six orders of magnitude larger than the strongest events on the sun (called superflares). These results provide a challenge for theorists working on hydrodynamical dynamo-models of partly convective stars with spectral type similar to the sun. This thesis presents a data analysis for the full data-set of Kepler-observations (observation time span 3,4 yr). A special aim of this work is to estimate an absolute and relative superflare frequency for sun-like Kepler-stars and to compare these results with the sun. Results of a rough reinvestigation of several so far known sun-like superflare stars are presented which turn out the necessity for a more detailed analysis strategy. A key aspect of the improved data analysis is to minimize the false alarm probability. Using the sample of sun-like stars within the Kepler field of view, a relative superflare frequency of one event per 100 yr for superflares with energies up to 1034 erg was estimated which is more than one order of magnitude larger than in previous studies.

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Kitze, Manfred: Untersuchung der Superflare-Aktivität bei sonnenartigen Sternen. Jena 2017.

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