Letter to the Editor

On the Wolf-Rayet counterpart to IC 10 X-1

¹ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
² Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH, UK

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

Received: 9 September 2003
Accepted: 19 December 2003

Abstract

Recent Chandra observations of the starburst galaxy IC 10 have resulted in an improved position for the bright (>10³⁸ erg s^-1) X-ray source IC 10 X-1. We discuss arguments in favour of the Wolf-Rayet star #17-A from Massey et al. and Crowther et al. being the optical counterpart; alternative possibilities are also considered. We discuss the properties of Massey et al. 17-A, finding it to be amongst the most luminous – and hence massive – WNE stars known and make comparisons with Cyg X-3. Finally we examine evolutionary constraints relating to the nature of the compact companion, finding that a putative neutron star companion would place stringent constraints on the minimum progenitor mass required to form a black hole in close binaries.