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Long-term stellar variability

Published online by Cambridge University Press:  26 February 2010

Isabella Pagano
Isabella Pagano*
Affiliation:
INAF - Osservatorio Astrofisico di Catania, v. Santa Sofia 78, p.le M. Rodonò, 95123Catania email: isabella.pagano@oact.inaf.it
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Abstract

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Stars with significant subsurface convection zones develop magnetic loop structures that, arising from the surface upward to the external atmospheres, cause flux variability detectable throughout the whole electromagnetic spectrum. In fact, diagnostics of magnetic activity are in radio wavelengths, where gyrosincrotron radiation arises from the quiescent and flaring corona; in the optical region, where important signatures are the Balmer lines, the Ca ii IRT and H&K lines; in the UV and X ray domains, the latter mainly due to coronal thermal plasma. The zoo of different magnetic features observed for the Sun – spots, faculae, flares, CMEs – are characterized by different temporal evolution and energetics, both in quantity and quality. As a consequence, the time scale of variability, the amount of involved energy and the quality of the involved photons are used as fingerprints in interpreting the observed stellar variability in the framework of the solar-stellar analogy. Here I review main results from long-term multiwavelength observations of cool star atmospheres, with emphasis to similarities and differences with the solar case.

Keywords

stars: activitystars: spotsstars: chromospheresstars: coronaestars: mass loss
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 5 , Symposium S264: Solar and Stellar Variability: Impact on Earth and Planets , August 2009 , pp. 136 - 145
Copyright
Copyright © International Astronomical Union 2010

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