Preliminary UVBY calibrations for G and K type dwarf stars.
Abstract
Four-color uvby photometry for several hundred late-type dwarf stars of types G, K and M is discussed. Mean values of photometric indices are given for MK spectral types between F8/G0V and M2V. Preliminary standard relations between the four-color indices are derived. Based on parallaxes and results from high-dispersion spectroscopic analyses, calibrations of the observed indices in terms of Mv, log Te and Fe/H have been derived. The means errors are 0.29 mag, 0.009 dex, and 0.17 dex, respectively. The calibrations are valid for class-V stars of all populations between G0 and M2. If extreme population-II dwarfs are excluded, the mean error of the abundance calibration decreases to 0.13 dex. Calibrations in terms of log g have been attempted,, but the low accuracy of the spectroscopic g determinations does not inspire confidence in the results. The possible contribution of a 'fourth-parameter' variation to the mean errors of the calibrations is briefly discussed. This fourth parameter could be the intrinsic helium abundance of the stars.
- Publication:
-
Astronomy and Astrophysics Supplement Series
- Pub Date:
- September 1984
- Bibcode:
- 1984A&AS...57..443O
- Keywords:
-
- Calibrating;
- Dwarf Stars;
- G Stars;
- K Stars;
- Late Stars;
- M Stars;
- Stellar Color;
- Stellar Spectrophotometry;
- Abundance;
- Astronomical Catalogs;
- Helium;
- Ubv Spectra;
- Astronomy