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Modulated stellar and solar cycles: parallels and differences

Published online by Cambridge University Press:  05 July 2012

K. Oláh
Affiliation:
Konkoly Observatory, Budapest, Hungary email: olah@konkoly.hu
L. van Driel-Gesztelyi
Affiliation:
Konkoly Observatory, Budapest, Hungary email: olah@konkoly.hu Mullard Space Science Laboratory, University College London, UK Observatoire de Paris, LESIA, CNRS, UPMC Univ. Paris 06, Univ. Paris-Diderot, Meudon Cedex, France
K. G. Strassmeier
Affiliation:
Leibniz Institute for Astrophysics Potsdam (AIP), Germany
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Abstract

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We present examples of activity cycle timescales on different types of stars from lowmass dwarfs to more massive giants, with wide-ranging rotation rates, and compare the observed cyclicities to the irradiance based solar cycle and its modulations. Using annual spectral solar irradiance in wavelength bands typical for stellar observations reconstructed by Shapiro et al. (2011), a direct comparison can be made between cycle timescales and amplitudes derived for the Sun and the stars. We show that cycles on multiple timescales, known to be present in solar activity, also show up on stars when the dataset is long enough to allow recognition. The cycle lengths are not fixed, but evolve – gradually during some periods but there are also changes on short timescales. In case the activity is dominated by spots, i.e., by cooler surface features, the star is redder when fainter, whereas other type of activity make the stars bluer when the activity is higher. We found the Sun to be a member of the former group, based on reconstructed spectral irradiance data by Shapiro et al. (2011).

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2012

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