Evolutionary status of population II Cepheids

Journal Article · Sun Feb 15 04:00:00 EST 1976 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/154156· OSTI ID:7194987

Gingold, R A

Several grids of post-horizontal-branch evolutionary models have been constructed assuming a range in either total mass or initial core mass on the horizontal branch. The less luminous Population II Cepheids (BL Herculis stars) are identified with stars of small envelope mass undergoing ''blueward noses'' from the asymptotic giant branch. These movements are due to readjustments between the hydrogen- and helium-burning shell luminosities following the exhaustion of helium in the core. The more luminous Cepheids (W Virginis stars) are identified with stars undergoing blueward loops from the second giant branch in response to helium shell flashes or finally evolving to the blue as the hydrogen-burning shell nears the stellar surface. The models predict relatively too few variables spread over too large a range in luminosity in the brighter group. Mass loss on the second giant branch is suggested to help resolve this problem. The assumption of a range in total mass on the zero-age horizontal branch produces a slightly better fit to the observed luminosity distribution of Population II Cepheids than does the assumption of a range in initial core mass. (AIP)

• Research Organization: Mount Stromlo and Siding Observatory, Research School of Physical Sciences, Australian National University
• OSTI ID: 7194987
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 204:1; ISSN ASJOA
• 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
CEPHEIDS
CRYOGENIC FLUIDS
ELEMENTS
FLUIDS
GIANT STARS
HELIUM
HYDROGEN
LUMINOSITY
MAIN SEQUENCE STARS
MASS
MATHEMATICAL MODELS
NONMETALS
NUCLEAR REACTIONS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RARE GASES
STAR EVOLUTION
STAR MODELS
STARS
VARIABLE STARS