RED SUPERGIANT STARS AS COSMIC ABUNDANCE PROBES. III. NLTE EFFECTS IN J-BAND MAGNESIUM LINES
- Max-Planck Institute for Astronomy, D-69117, Heidelberg (Germany)
- Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
- University of Liverpool (United Kingdom)
- Laboratoire Univers et Particules de Montpellier, Université Montpellier 2, CNRS, F-34095 Montpellier (France)
Non-local thermodynamic equilibrium (NLTE) calculations for Mg i in red supergiant stellar atmospheres are presented to investigate the importance of NLTE for the formation of Mg i lines in the NIR J-band. Recent work using medium resolution spectroscopy of atomic lines in the J-band of individual red supergiant stars has demonstrated this technique is a very promising tool for investigating the chemical composition of the young stellar population in star forming galaxies. As in previous work, where NLTE effects were studied for iron, titanium, and silicon, substantial effects are found resulting in significantly stronger Mg i absorption lines. For the quantitative spectral analysis the NLTE effects lead to magnesium abundances significantly smaller than in local thermodynamic equilibrium with the NLTE abundance corrections varying smoothly between −0.4 dex and −0.1 dex for effective temperatures between 3400 and 4400 K. We discuss the physical reasons of the NLTE effects and the consequences for extragalactic J-band abundance studies using individual red supergiants in the young massive galactic double cluster h and χ Persei.
- OSTI ID:
- 22522436
- Journal Information:
- Astrophysical Journal, Vol. 804, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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