Laws in Behaviour of NonLTE Effects for the NaI and MgI Atoms for K - a Stars.
Abstract
NonLTE calculations for the NaI and MgI atoms were performed for model atmospheres of T_ef = 4000 - 12000K, log g = 0.0 - 4.5, [M/H] = 0.5 - (-4). Departures from LTE result in strengthening the NaI spectral lines and weakening the MgI ones. For 8 NaI spectral lines and 9 MgI ones used usually in abundances determinations nonLTE abundance corrections were found. They are very individual for each spectral line and for specific parameters of stellar atmosphere. Even for the weakest spectral lines they are not small: they can reach to (-0.15dex) for the NaI lambdalambda615.4, 616.0nm and 0.17dex for the MgI lambda457.1nm, lambda571.1nm. The errors in abundances will be particularly large in the case of metal deficiency stars because the strong spectral lines are used in abundances determinations: for the NaI resonance lines nonLTE abundance corrections reach to (-0.8dex) and for the lambdalambda517.2, 518.3nm they consist of 0.3dex. We conclude that nonLTE analysis is necessary in each case of sodium or magnesium abundance determination.
- Publication:
-
Odessa Astronomical Publications
- Pub Date:
- 1996
- Bibcode:
- 1996OAP.....9...78M
- Keywords:
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- LINE: FORMATION;
- STARS: ATMOSPHERES;
- STARS: ABUNDANCES