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

March 2007 • 2007MNRAS.376..248H

Authors • Hadfield, L. J. • van Dyk, S. D. • Morris, P. W. • Smith, J. D. • Marston, A. P. • Peterson, D. E.

Abstract • 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.

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Schuyler Van Dyk

Senior Scientist