A study of M dwarfs. II. A grid of model atmospheres.
Abstract
A grid of M-dwarf model atmospheres is presented which covers the temperature range from 3000 to 4250 K as well as variations in composition and gravity. Line opacities are treated by using opacity distribution functions derived from statistical spectroscopy and the smeared-line model for diatomic molecules to deal with atomic-line and molecular-band blanketing. The temperature and pressure structure of each model is given as a function of the logarithm of the Rosseland mean optical depth; emergent fluxes longward of 5500 A are also presented. The relative flux calibration of red and IR colors is examined, and a calibration that is probably accurate to within a few per cent is employed to calculate the broadband colors. The main conclusions are that: (1) the emergent fluxes are dominated by TiO and H2O bands, (2) the turnover in J-H color index on the main sequence near 4000 K results from modification of the atmospheric structure by convection, (3) the near-IR continuum between 7500 and 12,000 A seems to offer the purest single temperature index, (4) the red TiO bands and the R-I color index show a marked dependence on metal abundance, and (5) the A-X band of CaH at 6900 A is sensitive to gravity.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- May 1976
- Bibcode:
- 1976A&A....48..443M
- Keywords:
-
- Atmospheric Models;
- Dwarf Stars;
- M Stars;
- Stellar Atmospheres;
- Astronomical Spectroscopy;
- Atmospheric Pressure;
- Atmospheric Temperature;
- Broadband;
- Diatomic Molecules;
- Stellar Models;
- Astrophysics