Searching for hidden Wolf-Rayet stars in the Galactic plane - 15 new Wolf-Rayet stars

• Published in: Monthly notices of the Royal Astronomical Society 2007-03, Vol.376 (1), p.248-262
• Main Authors: Hadfield, L. J., Van Dyk, S. D., Morris, P. W., Smith, J. D., Marston, A. P., Peterson, D. E.
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics; Earth, ocean, space; Exact sciences and technology; Galaxy: stellar content; Infrared imaging systems; Spectrum analysis; Stars & galaxies; stars: Wolf-Rayet
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2007.11424.x

We report the discovery of 15 previously unknown Wolf-Rayet (WR) stars found as part of an infrared (IR) broad-band study of candidate WR stars in the Galaxy. We have derived an empirically based selection algorithm which has selected ∼5000 WR candidate stars located within the Galactic plane drawn from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (mid-IR) and Two-Micron All-Sky Survey (near-IR) catalogues. Spectroscopic follow-up of 184 of these reveals 11 nitrogen-rich (WN) and four carbon-rich (WC) WR stars. Early WC subtypes are absent from our sample and none shows evidence for circumstellar dust emission. Of the candidates which are not WR stars, ∼120 displayed hydrogen emission-line features in their spectra. Spectral features suggest that the majority of these are in fact B supergiants/hypergiants, ∼40 of these are identified Be/B[e] candidates. Here, we present the optical spectra for six of the newly detected WR stars, and the near-IR spectra for the remaining nine of our sample. With a WR yield rate of ∼7 per cent and a massive star detection rate of ∼65 per cent, initial results suggest that this method is one of the most successful means for locating evolved, massive stars in the Galaxy.