O-star parameters from line profiles of wind-blanketed model atmospheres

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:6486630

Voels, S A

The basic stellar parameters (i.e. effective temperature, gravity, helium content, bolometric correction, etc...) of several O-stars are determined by matching high signal-to-noise observed line profiles of optical hydrogen and helium line transitions with theoretical line profiles from a core-halo model of the stellar atmosphere. The core-halo atmosphere includes the effect of radiation backscattered from a stellar wind by incorporating the stellar wind model of Abbott and Lucy as a reflective upper boundary condition in the Mihalas atmosphere model. Three of the four supergiants analyzed showed an enhanced surface abundance of helium. Using a large sample of equivalent width data from Conti a simple argument is made that surface enhancement of helium may be a common property of the most luminous supergiants. The stellar atmosphere theory is sufficient to determine the stellar parameters only if careful attention is paid to the detection and exclusion of lines which are not accurately modeled by the physical processes included. It was found that some strong lines which form entirely below the sonic point are not well modeled due to effects of atmospheric extension. For spectral class 09.5, one of these lines is the classification line He I {lambda}4471{angstrom}. For supergiant, the gravity determined could be systematically low by up to 0.05 dex as the radiation pressure due to lines is neglected. Within the error ranges, the stellar parameters determined, including helium abundance, agree with those from the stellar evolution calculations of Maeder and Maynet.

• Research Organization: Colorado Univ., Boulder, CO (USA)
• OSTI ID: 6486630
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
STARS
CHEMICAL COMPOSITION
GRAVITATION
COMPARATIVE EVALUATIONS
ELEMENT ABUNDANCE
HELIUM
STAR EVOLUTION
STAR MODELS
STELLAR ATMOSPHERES
STELLAR WINDS
SUPERGIANT STARS
ABUNDANCE
ATMOSPHERES
ELEMENTS
FLUIDS
GASES
GIANT STARS
MATHEMATICAL MODELS
NONMETALS
RARE GASES
STELLAR ACTIVITY
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources