Wolf-Rayet stars in M33 - II. Optical spectroscopy of emission-line stars in giant HII regions

Abstract

We present optical spectra of 14 emission-line stars in M33's giant HII regions NGC 592,595 and 604: five of them are known Wolf-Rayet (WR) stars, for which we present a better quality spectrogram, eight are WR candidates based on narrow-band imagery and one is a serendipitous discovery. Spectroscopy confirms the power of interference filter imagery to detect emission-line stars down to an equivalent width of about 5 Å in crowded fields. We have also used archival Hubble Space Telescope (HST)/WFPC2 (Wide Field and Planetary Camera 2) images to correctly identify emission-line stars in NGC 592 and 588.