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Paper: Temperature Variation on Spotted Stars
Volume: 349, Astrophysics of Variable Stars
Page: 193
Authors: Biazzo, K.; Frasca, A.; Catalano, S.; Marilli, E.; Tas, G.
Abstract: The photospheric temperature of active stars is affected by the contribution of surface features that are generally cooler than the surrounding photosphere. The knowledge of the starspot temperature and size is very important to understand the role and the effectiveness of the magnetic field in blocking the convective heating flux inside starspots. A reliable determination of the starspot temperature, however, is strongly hampered by the lack of solution uniqueness, as far as spot temperature and size are concerned.
A very sensitive diagnostics of surface temperature in late-type stars is the depth ratio of absorption lines in optical spectra.
In this work, we present and briefly discuss some results on spot size and temperature of stars with different gravity and activity level, i.e. solar-type main sequence stars and RS CVn-type giant stars derived from a combined analysis of light and temperature curves. The final scope of this project is to investigate any dependence of starspot characteristics from effective temperature and gravity — that is, to study the behaviour of surface inhomogeneities along the HR diagram. Our first results indicate that the starspot size and the difference between photospheric and starspot temperature are correlated to the star gravity, i.e. dwarf stars tend to have smaller and cooler (compared with their photosphere) spots than giant stars. Moreover, we cannot exclude a dependence of the starspot parameters on the activity level.
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