Rotation among Orion IC G stars : Angular momentum loss considerations in pre-main-sequence stars.
Abstract
Echelle spectra of the Na D lines or weak subordinate lines have been observed and analyzed for rotational velocities for 51 G type stars in the Orion Ic cluster. The high resolution of these MMT spectra permit a detection threshold VR sin i = 7 km s-1 or better to be attained. The results indicate that the velocity distribution of these stars can be represented by two components, a quasi-Maxwellian with a low modal value, <VR2 sin i>1/2 = 12 km s-1, and a flat distribution extending out to 200 km s-1. The D line spectra of the rapid rotators exhibit narrow absorption or emission features which are attributed to circumstellar disks close to the star. These disks appear to be quasi-permanent features and almost certainly are not remnants of the protostellar accretion phase. Several of the rapid rotators exhibit X-ray emission which also appears to be correlated with rotation. The implications of these results for the angular momentum problem in star formation are discussed in detail. It is suggested that a typical star loses some of its spin angular momentum to orbital momentum in a binary. This could occur by rotational synchronism during a protostellar fragmentation process.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1983
- DOI:
- 10.1086/161190
- Bibcode:
- 1983ApJ...271..237S
- Keywords:
-
- Angular Momentum;
- G Stars;
- Main Sequence Stars;
- Orion Nebula;
- Stellar Evolution;
- Stellar Rotation;
- Absorption Spectra;
- Abundance;
- D Lines;
- Emission Spectra;
- Hertzsprung-Russell Diagram;
- Stellar Envelopes;
- Stellar Spectrophotometry;
- Velocity Distribution;
- Astrophysics