A high galactic latitude survey of far-ultraviolet excess objects.
Abstract
This study presents optical spectra obtained for a selection of objects included in a catalog of far UV-bright, high-galactic-latitude objects detected with a balloon-borne survey telescope. The observed objects provide a sample of subdwarf O and B stars, white dwarfs, and binary systems including a hot subluminous member. Model-atmospheres analysis of the subdwarf sample is used to determine the temperature, gravity, and helium-to-hydrogen ratio of the individual objects. A smooth distribution of objects is found on the gravity-versus-temperature diagram near the theoretical location of the extended horizontal branch. A break between the helium-rich and helium-poor objects is found to occur at 40,000 K. Suspected binary objects were identified and analyzed to determine the temperature and gravity of the hot subluminous member in each system. The number of subdwarf stars contained in the binaries is determined at 65 to 100 percent. The proportion of white dwarfs that experience the subdwarf phase of evolution is found to be 0.94 percent.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 1991
- Bibcode:
- 1991A&A...250..370B
- Keywords:
-
- Faint Objects;
- Sky Surveys (Astronomy);
- Subdwarf Stars;
- Ultraviolet Astronomy;
- Astronomical Catalogs;
- Far Ultraviolet Radiation;
- Visible Spectrum;
- Astrophysics