Letter to the Editor

A newly identified Luminous Blue Variable in the galactic starburst cluster Westerlund 1^*

¹ Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, England, UK
² Dpto. de Física, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante, Apdo. 99, E03080 Alicante, Spain

Corresponding author: J. S. Clark, jsc@star.ucl.ac.uk

Received: 11 November 2003
Accepted: 27 November 2003

Abstract

We present observations of the massive transitional star W243 in Westerlund 1. We find an apparent spectral type of early-mid A from our data, in contrast to an earlier classification of B2I, made from data obtained in 1981. The concurrent development of a rich emission line spectrum suggests a very high mass loss rate; the continued presence of He i emission suggesting that the underlying star remains significantly hotter than implied by its apparent spectral type. We suggest that W243 is a Luminous Blue Variable undergoing an eruptive phase, leading to an extreme mass loss rate and the formation of a pseudo photosphere.