Understanding B-type supergiants in the low metallicity environment of the SMC II

¹ The Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Santa Cruz de La Palma, Canary Islands, Spain e-mail: ctrundle@iac.es
² The Department of Pure and Applied Physics, The Queen's University of Belfast, Belfast BT7 1NN, Northern Ireland

Received: 24 September 2004
Accepted: 5 January 2005

Abstract

Despite a resurgence of effort over the last decade in the area of massive stars there is still ambiguity over their evolutionary path, contamination of their surface abundances and the behaviour of their stellar winds. Here 10 SMC B-type supergiants are analysed applying a unified model atmosphere code fastwind to intermediate resolution spectra from the ESO Multi Mode Instrument (emmi) on the NTT telescope. Combined with the 8 targets analysed in Paper I (Trundle et al. 2004), this work provides observational results on the properties of the winds and chemical compositions of B-type supergiants in the SMC. This paper emphasizes and substantiates the implications for stellar evolution from Paper I; that current theoretical models need to produce larger degrees of surface nitrogen enhancements at lower rotational velocities. In addition a significant discrepancy between theoretical and observed mass-loss rates is discussed which will have important implications for the rotational velocities obtained from stellar evolution calculations. Furthermore, an initial calibration of the wind-momentum luminosity relationship for B-type supergiants in a low metallicity environment () is presented.