A RADIATION-DRIVEN DISC WIND MODEL FOR MASSIVE YOUNG STELLAR OBJECTS

A radiation-driven disc wind model is proposed that offers great promi se of explaining the extreme mass-loss signatures of massive young ste llar objects (the BN-type objects and more luminous Herbig Be stars). It is argued that the dense low-velocity winds associated with young l ate O/early B stars would be the consequence of continuing optically t hick accretion on to them. The launch of outflow from a Keplerian disc allows wind speeds of similar to 200 km s(-1) that are substantially less than the escape speed from the stellar surface. The star itself i s not required to be a rapid rotator. Disc irradiation is taken into a ccount in the hydrodynamical calculation presented, and identified as an important issue both observationally and from the dynamical point o f view.