Spicule-dominated coronae and late-type giant evolution

Journal Article · Thu Oct 01 04:00:00 EDT 1981 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/159273· OSTI ID:5730377

Wallenhorst, S G

The mass-loss rates and coronal temperatures of stars that have evolved away from the main sequence are examined, using an energy-balance model in which the coronal energy losses due to hot, downflowing spicular material are included. It is postulated that the coronal energy input flux remains constant as a star evolves up the red giant branch. stable solutions for a corona of this type are found to exist only below a critical stellar radius. The locus of these radii on the H-R diagram is identified with the Temperature Dividing Line (TDL) of Linsky and Haisch. If the total energy input flux has the value assumed (F/sub in/ = 1.3 x 10/sup 6/ ergs cm/sup -2/ s/sup -1/), then this constant-flux approach yields results which are consistent with the predictions of the minimum flux corona theory of Hearn; these similarities, along with the validity of the minimum flux technique, are discussed. It is shown that several criticisms of the theory are valid for minimum flux models in which spicular downflow is neglected, but are satisfied by the models considered here. As a star evolves across the TDL, we expect a jump in mass-loss rate of a factor of about 3.

• Research Organization: Washburn Observatory, University of Wisconsin
• OSTI ID: 5730377
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 249:1; 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
ATMOSPHERES
DIAGRAMS
ENERGY BALANCE
ENERGY LOSSES
ENERGY TRANSFER
GIANT STARS
HEAT TRANSFER
HERTZSPRUNG-RUSSELL DIAGRAM
LOSSES
MAIN SEQUENCE STARS
MATHEMATICAL MODELS
RADIATION EFFECTS
STAR EVOLUTION
STAR MODELS
STARS
STELLAR ATMOSPHERES
STELLAR WINDS
THERMAL CONDUCTION