Ultraviolet Studies of Horizontal Branch Stars and of Globular Clusters in the Milky Way and The Magellanic Cloud
Abstract
Ultraviolet data existing from two earlier orbiting instruments, the OAO-2 and the ANS, indicate the importance of carrying out spectroscopic investigations in the ultraviolet of globular clusters and horizontal branch stars. Because of the relative faintness of field horizortal branch stars, neither OAO-2 nor ANS observed a reasonable sample of these blue HB stars. In particular no such stars inside globular clusters have been measured individually. In order to fully interpret existing globular cluster UV fluxes, knowledge of horizontal branch stars is essential. Most population synthesis has been carried out by the use of model atmospheres or empirical data on population I stars. Current knowledge of the spectra of HB stars and the effects of line blanketing are very sketchy. We propose to observe such stars in the long and short wavelength range. OAO-2 and ANS observed only down to ~1400 A. Therefore several observations of globular clusters common to the OAO-2 and ANS data sets are of interest at wavelengths 1400 - 1100 A. This is the where the bluest stars dominate and as such is important for studies of stellar evolution. In addition we propose to observe some globular clusters in the magellanic clouds, where the difference in chemical composition may be important. All observations will be at low dispersion.
- Publication:
-
IUE Proposal
- Pub Date:
- 1979
- Bibcode:
- 1979iue..prop..178C