2003A&A...404..483C

We present Gemini-N GMOS and CFHT MOS spectroscopy of Wolf-Rayet candidates in the Local Group dwarf galaxy IC 10 that were previously identified by Massey et al. (1992AJ....103.1159M) and Royer et al. (2001A&A...366L...1R). From the present spectroscopic survey, the WC/WN ratio for IC 10 remains unusually high, given its low metallicity, although none of the WC9 stars suspected from narrow-band imaging are confirmed. Our spectroscopy confirms 9 newly discovered Wolf-Rayet candidates from Royer et al. (2001A&A...366L...1R), whilst spectral types of 14 Wolf-Rayet stars previously observed by Massey & Armandroff (1995AJ....109.2470M) are refined here. In total, there are 26 spectroscopically confirmed Wolf-Rayet stars in IC 10. All but one of the fourteen WC stars are WC4-6 stars, the exception being #10 from Massey et al. (1992AJ....103.1159M), a broad-lined, apparently single WC7 star. There are a total of eleven WN stars, which are predominantly early WN3-4 stars, but include a rare WN10 star, #8 from Royer et al. (2001A&A...366L...1R) #5 from Massey et al. (1992AJ....103.1159M) is newly identified as a transition WN/C star. Consequently, the WC/WN ratio for IC10 is 14/11∼1.3, unusually high for a metal-poor galaxy. Re-evaluating recent photometric data of Massey & Holmes (2002ApJ...580L..35M), we suggest that the true WC/WN ratio may not be as low as ∼0.3. Finally, we present ground-based finding charts for all confirmed WR stars, plus HST/WFPC2 charts for twelve cases.