Cycle times of early M dwarf stars: mean field models versus observations

Observations of early-type M stars suggest that there are two characteristic cycle times, one of order one year for fast rotators (Prot < 1 day) and another of order four years for slower rotators. For a sample of fast-rotating stars, the equator-to-pole differences of the rotation rates up to 0....

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Bibliographic Details
Published in:Proceedings of the International Astronomical Union 2019-06, Vol.15 (S354), p.116-119
Main Authors: Küker, Manfred, Rüdiger, Günther, Oláh, Katalin, Strassmeier, Klaus G.
Format: Article
Language:English
Subjects:
Astronomy
Contributed Papers
Convection
Cycle time
Dwarf stars
M stars
Magnetic fields
Meridional flow
Stellar rotation
Sun
Travel time
Velocity
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Summary:Observations of early-type M stars suggest that there are two characteristic cycle times, one of order one year for fast rotators (Prot < 1 day) and another of order four years for slower rotators. For a sample of fast-rotating stars, the equator-to-pole differences of the rotation rates up to 0.03 rad d−1 are also known from Kepler data. These findings are well-reproduced by mean field models. These models predict amplitudes of the meridional flow, from which the travel time from pole to equator at the base of the convection zone of early-type M stars can be calculated. As these travel times always exceed the observed cycle times, our findings do not support the flux transport dynamo.
ISSN:1743-9213
1743-9221
DOI:10.1017/S1743921319010007