ISSN:
1573-093X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract Center-to-limb measurements of the Ca i λ6573 intercombination line and the Ca ii λ7324 forbidden line are compared with synthetic profiles based on a simple representation of the non-LTE Ca-Ca+ ionization equilibrium. The effects of photoionizations from low lying excited states of neutral calcium are found to reduce the sensitivity of the λ6573 center-to-limb behavior as a thermal structure diagnostic. The synthetic center-to-limb behavior is also sensitive to uncertainties in the nonthermal broadening. Nevertheless, the measured center-to-limb behavior of λ6573 favors a ‘cool’ photospheric model similar to the Vernazza, Avrett, and Loeser model M over hotter models based on the Ca ii K wings. The non-LTE calcium abundance obtained from the disk center equivalent widths of λ6573 and λ7324 using the best fit model is A Ca≅2.1±0.2 × 10-6 (by number relative to hydrogen). Applications of these lines as diagnostics of the Ca-Ca+ ionization equilibrium in other stars are briefly discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00152329
