Astron. Astrophys. 320, 257-264 (1997)

The importance of a correct abundance assumption in determining the effective temperature and gravity of stars

A spectroscopic study of the helium weak stars HD5737, HD175362
and HD202671^*

F. Leone¹ and M. Manfrè²

¹ Osservatorio Astrofisico di Catania, Città Universitaria, I-95125 Catania, Italy
² Istituto di Astronomia, Università di Catania, Città Universitaria, I-95125 Catania, Italy

Received 3 May 1996 / Accepted 17 September 1996

Abstract

Even if metal and helium abundances characterize the stellar atmosphere structure, the effective temperature and gravity of stars are generally determined assuming the solar chemical composition. To investigate the importance of such a simplification, we have performed high resolution spectroscopy of the H region for the helium weak stars HD5737, HD175362 and HD202671, which are also known to be metal rich. By spectral synthesis of the H line profile, the effective temperature and gravity of these stars have been inferred using atmosphere models whose metal opacity scale, metal and helium abundances were consistent with the derived abundances. It appears that the effective temperature and gravity are under-estimated if the metal and/or the helium abundance are under-estimated. For HD175362 the richest in metal star of our sample, without taking into account the correct metal and helium abundance the effective temperature can be under-estimated up to 7% and the logarithm of gravity can be under-estimated up to 0.25 dex.

Key words: line: identification - stars: abundances - stars: chemically peculiar - stars: individual: HD5737, HD175362 and HD202671

^* Based on observations collected at the European Southern Observatory, LaSilla Chile.

Send offprint requests to: F. Leone

© European Southern Observatory (ESO) 1997

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