The dependence of coronal temperatures on Rossby numbers.
Abstract
Previous observations have shown that although correlations exist between chromospheric, transition region and coronal emission fluxes, the correlations between these fluxes and stellar rotational periods depend on the spectral type and luminosity class. The measured coronal temperatures (Tc) also depend on the type of star, with clear distinctions between F and G/K dwarf stars and between dwarf and giant stars. Others have argued that these emission fluxes, or luminosities, normalized to the stellar bolometric values can be related more closely to the Rossby number, Ro. Assuming that the coronal gas energy density depends only on the magnetic energy density a correlation is derived between the parameters Em(Tc) (the coronal emission measure), Tc, the surface gravity, and the required coronal magnetic field. This correlates well with the Rossby number for the dwarf stars. It is discussed how evolved stars might be included by also considering correlations with the dynamo number. Coronal temperatures and emission measures therefore provide an empirical way of investigating convection zone properties.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 1991
- DOI:
- 10.1093/mnras/252.1.21P
- Bibcode:
- 1991MNRAS.252P..21J
- Keywords:
-
- Dwarf Stars;
- Giant Stars;
- Rossby Regimes;
- Stellar Coronas;
- Stellar Rotation;
- Chromosphere;
- Iue;
- Stellar Evolution;
- Stellar Luminosity;
- Stellar Temperature;
- Astrophysics