Ultraviolet properties of hot stars in globular clusters

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:6609722

Altner, B M

Most of the interesting and important stages of stellar evolution beyond the horizontal branch (HB) occur in the temperature realms best investigated by ultraviolet (UV) astronomy. In this dissertation the author studies the UV properties of hot HB and post-HB stars found in a sample of galactic globular clusters, based on spectra obtained with the International Ultraviolet Explorer (IUE). Using techniques developed specifically for the purpose, he separates the overlapping spectra of individual hot stars in the crowded central regions of the clusters. He determines the physical properties of the separated core sources by comparing them to model stellar atmospheres, Population I standards, faint blue halo stars and previously known UV-bright cluster stars, from which he attempts to better understand their evolutionary status. The majority of the more than one hundred spatially separated components turn out to be individual blue HB stars, but a few have properties similar to those of the more evolved supra-HB stars or post-asymptotic-giant-branch (post-AGB) stars, substantially increasing the number of UV-bright stars found in galactic globular clusters. Derived properties of the post-AGB stars imply, through the use of the Paczynski mass-luminosity relation, that these stars span a very narrow range in total core mass, with a mean value near 0.55 Mass of sun - somewhat smaller than that derived for central stars of planetary nebulae in the galactic disk. Several of the clusters observed to have luminous ultraviolet sources in their cores have also shown the presence of a central cusp in the visual.

• Research Organization: Rutgers--the State Univ., New Brunswick, NJ (USA)
• OSTI ID: 6609722
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION SPECTRA
CHEMICAL COMPOSITION
COMPARATIVE EVALUATIONS
DWARF STARS
MASS
MASS TRANSFER
PHYSICAL PROPERTIES
SPECTRA
STAR CLUSTERS
STAR EVOLUTION
STARS
ULTRAVIOLET SPECTRA
WHITE DWARF STARS