White Dwarf Candidates in the Globular Cluster NGC 6752
Abstract
Spectral observations of five white dwarf candidates discovered in a search for faint blue objects near the globular cluster NGC 6752 are presented. The observations were obtained with a 4-m telescope in conjunction with a vidicon spectrograph at a dispersion of 376 A/mm, providing a resolution of 13 A/pixel. The spectral properties obtained indicate that F 110 is a very hot DO or subdwarf O star, WD 1 is a DC star, WD 2 is also a white dwarf, WD 18 and WD 12 are of type DA and WD 12 is a quasar with a redshift near 2. The H beta equivalent widths of two of the white dwarfs are shown to be consistent with those of other white dwarfs. Calculations of stellar properties assuming the white dwarfs to be members of NGC 6752 suggest that WD 2 and WD 12 are most likely foreground stars, while WD 1 and WD 18 most likely represent the first white dwarfs to be found in a globular cluster. The numbers of white dwarfs found or expected to be found in the cluster are interpreted to suggest that the plasma neutrino process is operating in nature.
- Publication:
-
IAU Colloq. 53: White Dwarfs and Variable Degenerate Stars
- Pub Date:
- 1979
- Bibcode:
- 1979wdvd.coll..259R
- Keywords:
-
- Globular Clusters;
- Stellar Spectra;
- White Dwarf Stars;
- Cosmic Plasma;
- Hertzsprung-Russell Diagram;
- O Stars;
- Quasars;
- Ubv Spectra;
- Astrophysics