Modelling the spectra of colliding winds in the Wolf–Rayet WC7+O binaries WR 42 and WR 79
1 iraf is distributed by the National Optical Astronomy Observatories, operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.
2 The emission line is a blend of multiplet 1 of C iv, multiplet 22 of C iii and perhaps even multiplet 15 of N iv. It has an effective wavelength of 5812 Å ( Underhill 1992), and so we shall hereafter refer to it simply as C ivλ5812 and adopt a rest wavelength of 5812.0 Å.
Abstract
We have obtained complete phase coverage of the WC7+O binaries WR 42 = HD 97152 and WR 79 = HD 152270 with high signal-to-noise ratio (S/N), moderate-resolution spectra. Remarkable orbital phase-locked profile variations of the C iiiλ5696 line are observed and interpreted as arising from colliding wind effects. Within this scenario, we have modelled the spectra using a purely geometrical model that assumes a cone-shaped wind–wind interaction region which partially wraps around the O star. Such modelling holds the exciting promise of revealing a number of interesting parameters for WR+O binaries, such as the orbital inclination, the streaming velocity of material in the interaction region and the ratio of wind momentum flux. Knowledge of these parameters in turn leads to the possibility of a better understanding of WR star masses, mass-loss rates and wind region characteristics.
