Stellar model chromospheres. V. Alpha Centauri A (G2 V) and alpha Centauri B (Kl V)

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

DOI:https://doi.org/10.1086/154818· OSTI ID:7240241

Ayres, T R; Linsky, J L; Rodgers, A W; Kurucz, R L

We propose models for the upper photospheres and lower chromospheres of ..cap alpha.. Cen A and B based on a partial redistribution (PRD) analysis of the Ca II K line cores and damping wings. Coude spectrograms of the Ca II regions in these stars obtained with the Mount Stromlo 74 inch (1.9 m) telescope are calibrated by fitting the far wing profiles of K with synthetic fluxes based on radiative equilibrium (RE) models. The RE calibrations are verified by comparison with independent calibrations using Willstrop's absolute photometry and narrow band fluxes obtained at Mount Stromlo. Deviations of the empirical profiles from the RE fluxes in the inner wings of K suggest departures from radiative equilibrium in the upper photosphere of ..cap alpha.. Cen A comparable to those found previously for the Sun and Procyon. Alpha Cen B shows similar departures from RE when the effects of CO cooling near the temperature minimum are taken into account. We find similar ratios of T/sub min//T/sub eff/ for both stars, which are within the range of T/sub min//T/sub eff/ ratios determined previously for the Sun, Procyon, and Arcturus. In addition, we find similar mass column densities at the 8000 K levels of the ..cap alpha.. Cen A and B chromospheres comparable to those determined for the Sun and Procyon. Finally, ..cap alpha.. Cen A appears to be more evolved and possibly much older than the Sun, despite its similar chromosphere structure. (AIP)

• Research Organization: Joint Institute for Laboratory Astrophysics, University of Colorado and National Bureau of Standards
• OSTI ID: 7240241
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 210:1; 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
CHEMICAL COMPOSITION
ENERGY-LEVEL TRANSITIONS
EQUILIBRIUM
IONIZATION
LINE WIDTHS
LTE
MATHEMATICAL MODELS
RADIATION TRANSPORT
SPECTRA
STAR MODELS
STELLAR ATMOSPHERES