Microscopic diffusion and subdwarfs
P. Morel 1 and
A. Baglin 2
Received 16 November 1998 / Accepted 4 February 1999
The recent distance determinations by HIPPARCOS have allowed to locate very precisely a reasonable set of subdwarfs in the HR diagram. A detailed comparison with evolutionary models is now possible and it has been recently claimed that the observed lower part of the main-sequence is cooler than the computed one. In this paper we show that microscopic diffusion could be the physical explanation of such a systematic shift. We emphazise the fact that, as diffusion alters surface abundances, the initial metal content of the stellar material is higher than the present one. A "calibration" procedure is necessary when comparing observed and theoretical HR diagram, to take into account this effect.
Key words: diffusion stars: Hertzsprung Russel (HR) and C-M diagrams stars: late-type
Send offprint requests to: P. Morel
Correspondence to: Pierre.Morel@obs-nice.fr
This article contains no SIMBAD objects.
© European Southern Observatory (ESO) 1999
Online publication: April 12, 1999