A search for rapid spectroscopic variability in the early-type supergiants Gamma and Theta Ara.
Abstract
High dispersion spectra of the Si III 5442-74 A triplet and H-alpha show variable line profiles for Gamma Ara and Theta Ara. The Si III lines are asymmetric, with changes occurring even within one hour. These observations are reminiscent of, though not identical to, the Smith and Ebbets (1981) observations of Rho Leo, for which a multimode nonradial pulsation basis was suggested. The behavior of Gamma Ara may also be described in these terms, although Theta Ara, being 2500 K cooler, did not exhibit a similar behavior. It is tentatively suggested that during the first of the two distinct change periods observed for Theta Ara, where blue and red asymmetries were found in the Si II and H-alpha lines, convective motions distorted the profiles. These motions ceased due to the sudden onset of a stronger net outward flow of matter or a change in convective region location or thickness.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 1983
- Bibcode:
- 1983A&A...124..211B
- Keywords:
-
- Early Stars;
- Stellar Oscillations;
- Stellar Spectra;
- Supergiant Stars;
- Variable Stars;
- H Alpha Line;
- Line Spectra;
- Silicon;
- Astronomy