Hostname: page-component-7c8c6479df-24hb2 Total loading time: 0 Render date: 2024-03-27T02:59:48.396Z Has data issue: false hasContentIssue false

Influence of Departures from LTE on Oxygen Abundance Determination in the Atmospheres of A – K stars

Published online by Cambridge University Press:  06 January 2014

Tatyana Sitnova
Affiliation:
Institute of Astronomy, Russian Academy of Sciences, Moscow 119017, Russia email: sitnova@inasan.ru
Lyudmila Mashonkina
Affiliation:
Institute of Astronomy, Russian Academy of Sciences, Moscow 119017, Russia email: sitnova@inasan.ru
Gang Zhao
Affiliation:
National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
Tatiana Ryabchikova
Affiliation:
Institute of Astronomy, Russian Academy of Sciences, Moscow 119017, Russia email: sitnova@inasan.ru
Yury Pakhomov
Affiliation:
Institute of Astronomy, Russian Academy of Sciences, Moscow 119017, Russia email: sitnova@inasan.ru
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Solar oxygen abundance is a key parameter for the studies of solar physics. Oxygen abundances of cool stars with different metallicities are important for understanding the galactic chemical evolution. We present non-LTE calculations for O I with the classical plane-parallel (1D) model atmospheres for a set of stellar parameters corresponding to stars of spectral types from A to K. Non-LTE leads to strengthening the O I lines, and the difference between the non-LTE and LTE abundances (non-LTE correction) is negative. The departures from LTE grow toward higher effective temperature and lower surface gravity. In the entire temperature range and log g = 4, the non-LTE correction does not exceed 0.05 dex in absolute value for lines of O I in the visible spectral range. The non-LTE corrections are significantly larger for the infrared O I 7771-5, 8446 Å lines and reach an order of magnitude for A-type stars. To differentiate the effects of inelastic collisions with electrons and neutral hydrogen atoms on the statistical equilibrium (SE) of O I, we derived the oxygen abundance for the five well studied A-type stars. For each star, non-LTE largely removes the difference between the infrared and visible lines found in LTE. In the case of cool stars (Sun and Procyon), inelastic collisions with H I affect the SE of O I, and agreement between the abundances from different lines is achieved when using the Drawin's formalism for collisional rates calculations. The solar mean oxygen abundance from the six lines is ϵ = 8.74 ± 0.05, when using the MAFAGS-OS solar model atmosphere and ϵ = 8.78 ± 0.03, when applying the 3D corrections taken from the literature. The non-LTE abundances of oxygen are derived for the sample of cool dwarfs with various metallicities on high-resolution spectra observed in the Lick observatory.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2014 

References

Allende Prieto, C., Asplund, M., Fabiani Bendicho, P. 2004 A&A, 423, 1109Google Scholar
Asplund, M., Grevesse, N., Sauval, A. J.et al. 2004 A&A, 417, 751Google Scholar
Allende Prieto, C., Asplund, M., Fabiani Bendicho, P. 2004 A&A, 423, 1109Google Scholar
Barklem, P. S. 2007, A&A, 462, 781Google Scholar
Butler, K., Giddings, J., 1985 Newsletter on Analysis of Astron. Spectra 9, Univ. of London, 723Google Scholar
Caffau, E., Ludwig, H. G., Steffen, M.et al. 2008, A&A 488 I3, 1031Google Scholar
Chen, Y., Zhao, G., Mashonkina, L.et al. 2014, this volumeGoogle Scholar
Drawin, H. W. 1968 Z. Physik, 211, 404Google Scholar
Drawin, H. W. 1969 Z. Physik, 225, 483CrossRefGoogle Scholar
Fossati, L., Bagnulo, S., Monier, R.et al. 2007, A&A 476, 911Google Scholar
Fossati, L., Ryabchikova, T., Bagnulo, S.et al. 2009, A&A 503, 945Google Scholar
Grupp, F., Kurucz, R. L., Tan, K. 2009, A&A, 503, 177Google Scholar
Gustafsson, B., Edvardsson, B., Eriksson, K.et al. 2008, A&A 486, 951Google Scholar
Przybilla, N., Butler, K., Becker, S. R.et al. 2000, A&A, 359, 1085Google Scholar
Ramirez, I., Allende Prieto, C. and Lambert, D. L. 2013, ApJ, 764, 78CrossRefGoogle Scholar
Reetz, J. 1999 Astrophysycs and Space Sience 265, 171CrossRefGoogle Scholar
Shulyak, D., Tsymbal, V., Ryabchikova, T.et al. 2004 A&A 428, 993Google Scholar
Sitnova, T., Mashonkina, L., Ryabchikova, T. 2013 Astronomy letters 39, 2, 126Google Scholar