next previous
Up: Abstract

A&A Supplement series, Vol. 123, May II 1997, 83-92

Received August 5; accepted September 9, 1996

An analysis of the currently available calibrations in Strömgren photometry by using open clusters

C. Jordi - E. Masana - F. Figueras - J. Torra

Send offprint request: C. Jordi;e-mail:
Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Avda. Diagonal 647, E-08028 Barcelona, Spain


In recent years, several authors have revised the calibrations used to compute physical parameters (tex2html_wrap_inline1601, tex2html_wrap_inline1603, log g, [Fe/H]) from intrinsic colours in the tex2html_wrap_inline1607 photometric system. For reddened stars, these intrinsic colours can be computed through the standard relations among colour indices for each of the regions defined by Strömgren (1966) on the HR diagram.

We present a discussion of the coherence of these calibrations for main-sequence stars. Stars from open clusters are used to carry out this analysis. Assuming that individual reddening values and distances should be similar for all the members of a given open cluster, systematic differences among the calibrations used in each of the photometric regions might arise when comparing mean reddening values and distances for the members of each region.

To classify the stars into Strömgren's regions we extended the algorithm presented by Figueras et al. (1991) to a wider range of spectral types and luminosity classes.

The observational ZAMS are compared with the theoretical ZAMS from stellar evolutionary models, in the range tex2html_wrap_inline1609 K. The discrepancies are also discussed.

keywords: stars: fundamental parameters -- open clusters and associations: general -- stars: distances -- HR diagram -- stars: general -- techniques: photometric

Copyright by the European Southern Observatory (ESO)