Abundance analysis of 5 early-type stars in the young open cluster IC 2391

¹ Institute of Astronomy (IfA), University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
² European Southern Observatory, Casilla 19001, Santiago 19, Chile
³ Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Hwy. Kamuela, Hawaii 96743, USA
⁴ Astrophyisics & Planetary Science Research Division, Department of Physics and Astronomy, The Queen's University of Belfast, University Road, Belfast, BT7 1NN, UK

Received: 25 July 2005
Accepted: 23 January 2006

Abstract

Aims.It is unclear whether chemically peculiar stars of the upper main sequence represent a class completely distinct from normal A-type stars, or whether there exists a continuous transition from the normal to the most peculiar late F- to early B-type stars. A systematic abundance analysis of open cluster early-type stars would help to relate the observed differences of the chemical abundances of the photospheres to other stellar characteristics, without being concerned by possible different original chemical composition. Furthermore, if a continuous transition region from the very peculiar to the so called normal A–F stars exists, it should be possible to detect objects with mild peculiarities.

Methods.As a first step of a larger project, an abundance analysis of 5 F–A type stars in the young cluster IC 2391 was performed using high resolution spectra obtained with the UVES instrument of the ESO VLT.

Results.Our targets seem to follow a general abundance pattern: close to solar abundance of the light elements and iron peak elements, heavy elements are slightly overabundant with respect to the sun, similar to what was found in previous studies of normal field A-type stars of the galactic plane. We detected a weakly chemically peculiar star, HD 74044. Its element pattern contains characteristics of CP1 as well as CP2 stars, enhanced abundances of iron peak elements and also higher abundances of Sc, Y, Ba and Ce. We did not detect a magnetic field in this star (detection limit was 2 kG). We also studied the star SHJM 2, proposed as a pre-main sequence object in previous works. Using spectroscopy we found a high surface gravity, which suggests that the star is very close to the ZAMS.