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Magnetic Activity of Two Similar Subgiants in Binaries with Very Different Mass Ratios: EI Eri and V711 Tau

Published online by Cambridge University Press:  23 April 2012

Katalin Oláh
Affiliation:
Konkoly Observatory, Konkoly Thege út 15-17., H-1121 Budapest, Hungary email: [email protected], [email protected], [email protected]
Zsolt Kővári
Affiliation:
Konkoly Observatory, Konkoly Thege út 15-17., H-1121 Budapest, Hungary email: [email protected], [email protected], [email protected]
Krisztián Vida
Affiliation:
Konkoly Observatory, Konkoly Thege út 15-17., H-1121 Budapest, Hungary email: [email protected], [email protected], [email protected]
Klaus G. Strassmeier
Affiliation:
Leibniz Institute for Astrophysics Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany email: [email protected]
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Abstract

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We use more than three decades-long photometry to study the activity patterns on the two fast-rotating subgiant components in EI Eri (G5IV) and V711 Tau (K1IV). From yearly mean rotational periods from the light curves, we find that EI Eri, with well-measured solar-type differential rotation, always has spots from the equator to high latitudes. The measured differential rotation of V711 Tau is controversial, and in any case is very small. The spots on the K1IV star in V711 Tau seem to be tidally locked. The physical parameters of the two systems are similar, with one remarkable difference: EI Eri has a low mass M4-5 dwarf companion, whereas V711 Tau has a G5V star in the system, thus their mass centers are in very different positions. This may modify the whole internal structure of the active stars, causing marked differences in their surface features.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2012

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