A chemical analysis of five hot stars towards the Galactic centre

¹ Department of Pure & Applied Physics, The Queen's University of Belfast, BT7 1NN, Northern Ireland, UK
² Institute for Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OBA,UK
³ Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, Scotland, UK

Corresponding author: P. L. Dufton, p.dufton@qub.ac.uk

Received: 21 October 2003
Accepted: 15 February 2004

Abstract

High resolution echelle spectroscopy is presented for thirteen stars lying in the direction of the Galactic centre which, on the basis of photographic photometry and low dispersion spectroscopy, have been classified as early-B-type. Eight of these stars have large rotational velocities which preclude a detailed analysis. The five stars with moderate to low projected rotational velocities have been analysed using model atmosphere techniques to determine atmospheric parameters and chemical compositions. Two of these stars appear to be evolved blue horizontal branch objects on the basis of their chemical compositions and small projected rotational velocity. The evolutionary status of a third is ambiguous but it is probably a post-asymptotic-giant branch star. The remaining two objects are probably young massive stars and show enhanced abundances of N, C, Mg and Si, consistent with their formation in the inner part of the Galactic disk. However their O abundances are normal, confirming results found previously for other early-type stars, which would imply a flat abundance gradient for this element in the inner region of our Galaxy.