WR146 - observing the OB-type companion

Abstract

We present new radio and optical observations of the colliding-wind system WR146 aimed at understanding the nature of the companion to the Wolf-Rayet star and the collision of their winds. The radio observations reveal emission from three components: the WR stellar wind, the non-thermal wind-wind interaction region and, for the first time, the stellar wind of the OB companion. This provides the unique possibility of determining the mass-loss rate and terminal wind velocity ratios of the two winds, independent of distance. Respectively, these ratios are determined to be 0.20+/-0.06 and 0.56+/-0.17 for the OB-companion star relative to the WR star. A new optical spectrum indicates that the system is more luminous than had been believed previously. We deduce that the ``companion'' cannot be a single, low luminosity O8 star as previously suggested, but is either a high luminosity O8 star, or possibly an O8+WC binary system.Comment: 9 pages, 5 figures, ftp://fto.drao.nrc.ca/pub/smd/wr146/accepted.ps.gz To be published in Monthly Notices of the Royal Astronomical Societ