Far-ultraviolet spectra of the nuclei of globular clusters M 30, M 54, M 70.
Abstract
IUE spectra in the low dispersion mode have been collected from the nuclei of the three galactic globular clusters NGC 6681 (= M70), NGC 6715 (= M54), and NGC 7099 (= M30). High UV fluxes are obtained from M54 which had been found earlier to be a real characteristic of the cluster population, suggesting a possible connection of this cluster with EB clusters as defined by van Albada et al. (1981). Although the B and EB clusters anticorrelate as groups with metallicity, the flux level in M70 suggests that within the EB group UV colors and metallicity are again correlated. A point-like UV source has been detected at the center of M30. Separation between the central source and the diffuse cluster background radiation has been achieved through a multi-Gaussian best-fit procedure. The diffuse component shows the behavior of B-type clusters, in accordance with ANS data. The point-like source is shown to be a star in a post-HB phase crossing the HR diagram towards the asymptotic giant branch.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 1984
- Bibcode:
- 1984A&A...138..485C
- Keywords:
-
- Astronomical Spectroscopy;
- B Stars;
- Far Ultraviolet Radiation;
- Globular Clusters;
- Horizontal Branch Stars;
- Sagittarius Constellation;
- Ultraviolet Spectra;
- Asymptotic Giant Branch Stars;
- Hertzsprung-Russell Diagram;
- Iue;
- Normal Density Functions;
- Spaceborne Astronomy;
- Astrophysics