Spectrophotometry of Wolf-Rayet Stars: Intrinsic Colors and Absolute Magnitudes

Abstract

We present ~10 A resolution absolute spectrophotometry in the range λ 3400-7300 for southern Wolf-Rayet stars, including most of the known WR stars in the LMC, and λ 3400-4700 spectrophotometry of all WR stars in the SMC. The data are used to investigate the continuum properties of WR by con- structing essentially line-free magnitudes and colors. We find that the emission-line contamination in the narrowband ubvr system of Westerlund and Smith is small for most WN stars, but is quite significant for WC stars. The differences in intrinsic colors from star to star of the same spectral subtype are more severe at shorter wavelengths, and we argue that this is likely due to differences in atmospheric extent, similar to earlier suggestions. For the LMC WR stars we derive true continuum absolute visual magnitudes and intrinsic colors. We find that WN stars of type WN6 and later are significantly more luminous visually (<M_v_> ~ -6.3) than those of earlier type (<M_v_> ~ -3.8 for WN3-4), as has previously been recognized. The most visually luminous WN6-WN7 stars are located in the core of the 30 Doradus region. The visual absolute magnitude of WC4 stars (the only type of WC stars in the LMC) is comparable to that of the early WN stars. WR stars whose spectra show absorption lines are significantly brighter at each spectral type, consistent with their being due to a companion star, although in some cases the absorption lines may be intrinsic to the WR star. The spectrophotometry is available on tape from the Astronomical Data Center.