Ultraviolet Survey for Hot Companions among Nonvariable Yellow Supergiants
Abstract
Twenty nonvariable yellow supergiants have been observed for the first time with the International Ultraviolet Explorer satellite, with the aim of discovering hot companions. Two newly discovered systems are announced: HD 74395 (G2 I + B9.5 IV-V) and HD 193469 (later than G0 + B8 IV-V). The Cepheid HD 9250 was also observed, but no hot companion was found. Some stars independently known to have a hot companion were included in order to study the properties of the companions and to compare with previous work. Atmospheric models were used to fit the overall energy distribution of the binary system, allowing an estimate of Te, log g, and the spectral type of the companion. The magnitude differences, in the V band, between the yellow supergiants and their companions were calculated. The possibility of using this magnitude difference and the spectral type determined for the hot companions to estimate M(v) for the yellow supergiants and the distance to the systems is explored. Comparison of the binaries' positions in the H-R diagram with theoretical evolutionary tracks suggests that the masses of the primaries are contained between 5 and 9 solar masses and that, on average, they are about twice as massive as their hot companions.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1986
- DOI:
- 10.1086/164039
- Bibcode:
- 1986ApJ...302..767A
- Keywords:
-
- Binary Stars;
- Cepheid Variables;
- Companion Stars;
- Hot Stars;
- Supergiant Stars;
- Ultraviolet Astronomy;
- Hertzsprung-Russell Diagram;
- Iue;
- Spectral Energy Distribution;
- Stellar Atmospheres;
- Stellar Magnitude;
- Stellar Mass;
- Stellar Spectra;
- Stellar Temperature;
- Astrophysics;
- STARS: BINARIES;
- STARS: CEPHEIDS;
- STARS: SUPERGIANTS;
- ULTRAVIOLET: SPECTRA