The enigmatic Half line of FK COM : last stages of a coalescing binary ?
Abstract
The apparently single, rapidly rotating G giant FK Comae displays an unusual hydrogen alpha emission line which is very broad, strong, and variable. Extensive high-resolution studies of this line with complete phase coverage are presented. The alpha hydrogen emission centroid shows a radial velocity modulation on the 2.4 days stellar rotation period with a semiamplitude identical to the photospheric rotational velocity. These data, when phased with optical photometry, indicate that the star has a bright, rather than dark, region on its surface and that the phase may have been stable for seven years. A qualitative model wherein the bright spot is caused by accretion from a low mass unseen companion onto the surface of the G giant is considered. Such a model explains many of the observed characteristics of the stellar spectrum and hydrogen alpha feature, and it is concluded that FK Comae is not yet a single star, but is still evolving toward coalescence of the system.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1982
- DOI:
- 10.1086/160293
- Bibcode:
- 1982ApJ...260..735W
- Keywords:
-
- Binary Stars;
- Emission Spectra;
- G Stars;
- H Alpha Line;
- Stellar Evolution;
- Stellar Spectra;
- Stellar Spectrophotometry;
- High Resolution;
- Photosphere;
- Radial Velocity;
- Radiant Flux Density;
- Spectral Line Width;
- Spectral Resolution;
- Stellar Mass Accretion;
- Stellar Models;
- Stellar Rotation;
- Visual Photometry;
- Astrophysics