CP stars: Photometric calibrations of luminosity using HIPPARCOS data
Jordi, C.; Luri, X.; Figueras, F.; Masana, E.; Torra, J.; Mennessier, M. O.; Domingo, A.; Gomez, A. E.; Grenier, S.; Blasi, F.
Spain, France
Abstract
The application of the Stromgren photometric luminosity calibrations to different types of CP stars is reexamined in the light of the new Hipparcos data. A first attempt is made to use the LM statistical parallax method - based on the maximum likelihood principle - to obtain a calibration of the absolute magnitude as a function of two Stromgren colour indices, thus reflecting effective temperature and evolution. Its application to a sample of Si stars and to a sample of normal main sequence stars in the same spectral range allows us to compare the calibrations obtained and to discuss the position of Si stars in the HR diagram. Additionally, a sample of "bonafide", spectroscopically selected Am stars together with normal main sequence stars are used to derive a new absolute magnitude calibration for late A-type main sequence stars, taking into account the effects of evolution, metallicity and stellar rotation.