Showing papers by "Pierre Royer published in 2003"

Gemini observations of Wolf-Rayet stars in the Local Group starburst galaxy IC 10

Abstract: 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. and Royer et al. 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., whilst spectral types of 14 Wolf-Rayet stars previously observed by Massey & Armandroff 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., 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. # 5 from Massey et al. is newly identified as a transition WN/C star. Consequently, the WC/WN ratio for IC10 is 14/11similar to1.3, unusually high for a metal-poor galaxy. Re-evaluating recent photometric data of Massey & Holmes, we suggest that the true WC/WN ratio may not be as low as similar to0.3. Finally, we present ground-based finding charts for all confirmed WR stars, plus HST/WFPC2 charts for twelve cases.

Gemini observations of Wolf-Rayet Stars in the Local Group Starburst Galaxy IC10

Abstract: We present Gemini-N GMOS and CFHT MOS spectroscopy of Wolf-Rayet candidates in the Local Group dwarf galaxy IC10 that were previously identified by Massey et al. and Royer et al. From the present spectroscopic survey, the WC/WN ratio for IC10 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., whilst spectral types of 14 Wolf-Rayet stars previously observed by Massey & Armandroff 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., 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. #5 from Massey et al. 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, 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.

Wolf-Rayet stars at 1 - 2 Mpc

Abstract: We present new narrow-band imaging and optical spectroscopy of Wolf-Rayet stars in the Local Group dwarf galaxy IC 10 (Gemini-N- gmos) and Sculptor group spiral galaxy NGC 300 (VLT fors2)

Classification of Wolf-Rayet stars in NGC 595 in M 33 through high-spatial resolution observations

Abstract: NGC 595 is, after NGC 604, the second most luminous HII region in theMilky Ways neighbouring spiral galaxy M 33. Its Wolf-Rayet starcontent has mainly been unveiled by two different channels. On the onehand, the stellar population of NGC 595 has been resolved and its WRstars identified through on-line/off-line HeIIlambda4686 observationsrealised with the HST. Nevertheless, due to the limited number offilters used, this did not give any information on the WR spectralsubtypes. On the other hand, spectroscopic observations of NGC 595,realised at optical and ultraviolet wavelengths, have enabled thedetermination of some spectral subtypes, but this time, the lack ofangular resolution did not allow to resolve the whole population.Thanks to our photometric technique, based on five dedicated narrow-bandfilters, we present here a determination of the spectral subtypes of NGC595 WR stars which for the first time combines high-angular resolutionand high-spectroscopic discrimination capabilities. (Less)