Magnetohydrostatic equilibrium in starspots: dependences on color (T_{eff}) and surface gravity (g)
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}.
Keywords
Cite
@article{arxiv.1010.0126,
title = {Magnetohydrostatic equilibrium in starspots: dependences on color (T_{eff}) and surface gravity (g)},
author = {S. P. Rajaguru and S. S. Hasan},
journal= {arXiv preprint arXiv:1010.0126},
year = {2015}
}
Comments
4 pages, 3 figures, to appear in the Proceedings of IAUS 273: "Physics of Sun and Star Spots", eds. D.P. Choudhary and K. Strassmeier 2010, Cambridge University Press