THE MASSES OF POPULATION II WHITE DWARFS
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)
- Departement de Physique, Universite de Montreal, C.P. 6128, Succ. Centre-Ville, Montreal, QC H3C 3J7 (Canada)
- Departamento de AstronomIa y Astrofisica, Pontificia Universidad Catolica de Chile, Av. Vicuna Mackenna 4860, 782-0436 Macul, Santiago (Chile)
Globular star clusters are among the first stellar populations to have formed in the Milky Way, and thus only a small sliver of their initial spectrum of stellar types are still burning hydrogen on the main sequence today. Almost all of the stars born with more mass than 0.8 M{sub sun} have evolved to form the white dwarf cooling sequence of these systems, and the distribution and properties of these remnants uniquely holds clues related to the nature of the now evolved progenitor stars. With ultra-deep Hubble Space Telescope imaging observations, rich white dwarf populations of four nearby Milky Way globular clusters have recently been uncovered, and are found to extend impressive 5-8 mag in the faint-blue region of the Hertzsprung-Russell diagram. In this paper, we characterize the properties of these population II remnants by presenting the first direct mass measurements of individual white dwarfs near the tip of the cooling sequence in the nearest of the Milky Way globulars, M4. Based on Gemini/GMOS and Keck/LRIS multiobject spectroscopic observations, our results indicate that 0.8 M{sub sun} population II main-sequence stars evolving today form 0.53 +- 0.01 M{sub sun} white dwarfs. We discuss the implications of this result as it relates to our understanding of stellar structure and evolution of population II stars and for the age of the Galactic halo, as measured with white dwarf cooling theory.
- OSTI ID:
- 21378371
- Journal Information:
- Astrophysical Journal, Vol. 705, Issue 1; Other Information: DOI: 10.1088/0004-637X/705/1/408; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Atomic Absorption Line Diagnostics for the Physical Properties of Red Supergiants
THE AGE AND STELLAR PARAMETERS OF THE PROCYON BINARY SYSTEM