Excitation of pulsations in the CNO ionization zone of luminous stars

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

DOI:https://doi.org/10.1086/154234· OSTI ID:7365123

Stothers, R

A new source of excitation for stellar pulsations has been discovered by employing Carson's new radiative opacities in models of chemically homogeneous stars. These opacities have a ''bump'' arising from the ultimate ionization of the CNO elements at moderate temperatures and very low densities. Such high opacities induce in the envelopes of the more massive stars a strong local convection zone, a high central condensation (which renders the pulsational epsilon-mechanism ineffective), and pulsational instability via the kappa-mechanism above a certain stellar mass. This mass for Population I hydrogen-burning stars is very uncertain, but is probably greater than approx.45 M/sub sun/ for the fundamental radial mode, with the overtones being more stable. For homogeneous helium-burning stars, the critical mass lies somewhere in the range 2--6 M/sub sun/ for all modes up to at least the third overtone. Pulsational stability at any stellar mass can be decreased by adopting a larger metals abundance, a brighter luminosity, a higher effective temperature, a smaller rate of axial rotation, a shorter convective mixing length, or a greater adaptability of convection to the pulsations. (AIP)

• Research Organization: Institute for Space Studies, Goddard Space Flight Center, Greenbelt, MD
• OSTI ID: 7365123
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 204:3; 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
ATMOSPHERES
CARBON
CEPHEIDS
CONVECTION
CRYOGENIC FLUIDS
DIAGRAMS
ELEMENTS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITATION
FLUIDS
HEAT TRANSFER
HELIUM
HERTZSPRUNG-RUSSELL DIAGRAM
HYDROGEN
IONIZATION
LUMINOSITY
MASS
MATHEMATICAL MODELS
MOTION
NITROGEN
NONMETALS
OPACITY
OPTICAL PROPERTIES
OXYGEN
PHOTOSPHERE
PHYSICAL PROPERTIES
PULSATIONS
RARE GASES
ROTATION
SOLAR ATMOSPHERE
STAR MODELS
STARS
VARIABLE STARS