A fine analysis of calcium and iron lines in the spectrum of the subdwarf Groombridge 1830.
Abstract
A detailed model atmosphere analysis of calcium and iron lines is used to derive a set of self-consistent atmospheric parameter for the subdwarf Gmb 1830. T(eff) is found to be 5170 +/- 70 K, slightly hotter than previous estimates based on photometric indices. The surface gravity is slightly greater than that of the sun. There is a clear difference in logarithmic abundance, relative to the sun, between calcium and iron such that (Ca/H) exceeds (Fe/H) by about 0.3 dex. The logarithmic abundance of magnesium, relative to the sun, is close to that of calcium. Test calculations indicate that it is the relative abundance of alpha-particle elements, presumably mainly Mg and Si, which largely controls the electron pressure of the atmosphere. The microturbulence in Gmb 1830 is similar to that found in other G and early K type dwarf stars.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 1992
- Bibcode:
- 1992A&A...263..249S
- Keywords:
-
- Calcium;
- Iron;
- Stellar Composition;
- Stellar Spectra;
- Subdwarf Stars;
- Charge Coupled Devices;
- Metallicity;
- Stellar Atmospheres;
- Stellar Models;
- Stellar Spectrophotometry;
- Astrophysics