IUE observations of the M dwarfs CM Draconis and Rossiter 137B : magnetic activity at saturated levels.
Abstract
IUE observations of two active M dwarfs with known rotation rate or age and presumed to be almost totally convective are presented. The first of these stars, CM Draconis (Gl 630.1), is an old Population II binary with its components in tidally induced rapid rotation (P = 1.27 d, dM 4 + dM 4). The other one, Rossiter 137 B, forms with HD 36705 (AB Dor) a visual pair of young active stars. The activity of CM Dra is due to the forced rotation in a close binary, while Rst 137 B is assumed to rotate fast enough to generate its magnetica activity. These results are compared with those for M dwarfs, particularly AU Mic and YZ CMi, that have known rotational periods and measured ultraviolet emission line fluxes. The chromospheric-coronal saturation levels of cool dwarfs between 0.3 less than B-V less than 1.6 is determined. It is found that saturated F stars have stronger chromospheres than saturated M stars, but the opposite is true for the corona. Results of these observations seem to favor a rotation-dependent distributed dynamo generating magnetic flux in totally convective stars.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 1989
- Bibcode:
- 1989A&A...222..179V
- Keywords:
-
- Binary Stars;
- Dwarf Stars;
- M Stars;
- Stellar Activity;
- Stellar Spectrophotometry;
- Chromosphere;
- Emission Spectra;
- Iue;
- Stellar Magnetic Fields;
- Stellar Rotation;
- Astrophysics