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arXiv · 1010.0126

Magnetohydrostatic equilibrium in starspots: dependences on color (T_{eff}) and surface gravity (g)

S. P. Rajaguru·S. S. Hasan
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Abstract

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 T_{eff}, 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 T_{eff} due to a combination of pressure and opacity variations against T_{eff}.

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S. P. Rajaguru, S. S. Hasan. 2010-10-01. Magnetohydrostatic equilibrium in starspots: dependences on color (T_{eff}) and surface gravity (g). https://doi.org/10.1017/s1743921311015377

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