A Non--Local Thermodynamic Equilibrium, Line-blanketed Synthetic Spectrum of IOTA Herculis: C, Al, and SI Lines
Abstract
A non-LTE line-blanketed model stellar atmosphere is used to compute a model of I Herculis (B3 IV) with a Teff of 17,500 K and a log g of 3.75, following the conclusions of Peters and Polidan (1985). Detailed profiles of a number of lines of C, Al, and Si in the 1200-2000-A region are computed, including the resonance lines of C II, Al II, and Al III. These profiles are compared to observations obtained from the coaddition of eight IUE SWP images, using a technique developed by Leckrone and Adelman (1989). Comparison of carbon lines with a model that is underabundant in carbon by a factor of 2 relative to the sun indicates that the C abundance of Iota Her is at most one-half solar. Non-LTE effects are examined by comparing an LTE model possessing identical atmospheric parameters with the non-LTE model. Substantial differences in the populations of the model atomic states are found, but differences in the temperature structure of the two models often mask the non-LTE effects in the synthetic spectra.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1991
- DOI:
- 10.1086/170617
- Bibcode:
- 1991ApJ...380..606G
- Keywords:
-
- B Stars;
- Early Stars;
- Main Sequence Stars;
- Stellar Atmospheres;
- Stellar Spectra;
- Thermodynamic Equilibrium;
- Abundance;
- Aluminum;
- Carbon;
- Resonance Lines;
- Silicon;
- Stellar Models;
- Astrophysics;
- STARS: ABUNDANCES;
- STARS: ATMOSPHERES;
- STARS: EARLY-TYPE;
- ULTRAVIOLET: SPECTRA