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Magnetohydrostatic equilibrium in starspots: dependences on color (Teff) and surface gravity (g)

Published online by Cambridge University Press:  26 August 2011

S. P. Rajaguru  and
S. S. Hasan
S. P. Rajaguru
Affiliation:
Indian Institute of Astrophysics, Bangalore - 560034, India, email: [email protected]
S. S. Hasan
Affiliation:
Indian Institute of Astrophysics, Bangalore - 560034, India, email: [email protected]
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Abstract

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Temperature contrasts and magnetic field strengths of sunspot umbrae broadly follow the thermal-magnetic relationship obtained from magnetohydrostatic equilibrium. Using a compilation of recent observations, especially in molecular bands, of temperature contrasts of starspots in cool stars, and a grid of Kurucz stellar model atmospheres constructed to cover layers of sub-surface convection zone, we examine how the above relationship scales with effective temperature (Teff), surface gravity g and the associated changes in opacity of stellar photospheric gas. We calculate expected field strengths in starpots and find that a given relative reduction in temperatures (or the same darkness contrasts) yield increasing field strengths against decreasing Teff due to a combination of pressure and opacity variations against Teff.

Keywords

Sun: magnetic fieldssunspotsstars: magnetic fieldsstars: spotsstars: activity
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S273: The Physics of Sun and Star Spots , August 2010 , pp. 276 - 280
Copyright
Copyright © International Astronomical Union 2011

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