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.
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References
Auer, L. H.: 1976, J. Quant. Spectrosc, Radiat. Transf. 16, 931.
Auer, L. H., Heasley, J. N., and Milkey, R. W.: 1972, Kitt Peak National Observatory Contribution No. 555.
Avrett, E. H.: 1977a, private communication.
Avrett, E. H.: 1977b, in The Solar Output and Its Variation, Colorado Assoc. Univ. Press, Boulder, p. 327.
Ayres, T. R.: 1977a, Astrophys. J. 213, 296.
Ayres, T. R.: 1977b, Astrophys. J. 214, 905.
Ayres, T. R.: 1978a, Solar Phys. 57, 19.
Ayres, T. R.: 1978b, Astrophys. J. (in press).
Brault, J. and Tèsterman, L.: 1972, Kitt Peak Solar Atlas, preliminary edition, Kitt Peak National Observatory, Tucson.
Brault, J. W. and White, O. R.: 1971, Astron. Astrophys. 13, 169.
Brault, J. W., Slaughter, C. D., Pierce, A. K., and Aikens, R. S.: 1971, Solar Phys. 18, 366.
Carter, V. L., Hudson, R. D., and Brieg, E. L.: 1971, Phys. Rev. A4, 821.
Crandall, D. H., Dunn, G. H., Gallagher, A., Hummer, D. G., Kunasz, C. V., Leep, D., and Taylor, P. O.: 1974, Astrophys. J. 191, 789.
Evans, J. C. and Testerman, L.: 1975, Solar Phys. 45, 41.
House, L. L.: 1964, Astrophys. J. Suppl. 8, 307.
Kelm, S. and Schlüter, D.: 1962, Z. Astrophys. 56, 78.
Kneer, F.: 1975, Astrophys. J. 200, 367.
Linsky, J. L. and Ayres, T. R.: 1978, Astrophys. J. 220, 619.
Milkey, R. W.: 1976, in Interpretation of Atmospheric Structure in the Presence of Inhomogeneities, University of Sydney, Sydney, p. 55.
Okuno, Y.: 1971, J. Phys. Soc. Japan 31, 1189.
Ramsey, L. W.: 1977, Astrophys. J. 215, 827.
Schorn, R. A., Young, A. T., and Barker, E. S.: 1975, Solar Phys. 43, 9.
Smith, G.: 1967, Proc. Roy. Soc. London A297, 288.
Travis, L. D. and Matsushima, S.: 1968, Astrophys. J. 154, 689.
Ulmschneider, P.: 1974, Solar Phys. 39, 327.
van Regemorter, H.: 1962, Astrophys. J. 136, 906.
Vernazza, J. E., Avrett, E. H., and Loeser, R.: 1973, Astrophys. J. 184, 605.
Vernazza, J. E., Avrett, E. H., and Loeser, R.: 1976, Astrophys. J. Suppl. 30, 1 (VAL).
Withbroe, G. L.: 1977, Center for Astrophysics, preprint No. 524.
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Visiting Astronomer, Kitt Peak National Observatory.
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Ayres, T.R., Testerman, L. The center-to-limb behavior of Ca i λ6573 and [Ca ii] λ7324. Sol Phys 60, 19–29 (1978). https://doi.org/10.1007/BF00152329
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DOI: https://doi.org/10.1007/BF00152329