1994A&A...290..167B

In a high resolution (R=38000) spectroscopic survey of 33 Herbig Ae/Be stars we detected in 17 of them forbidden [OI]6300.31A emission. Among them, 8 also show detectable [OI]6363.79A emission. All of these stars, except one, possess forbidden lines, which are centered on the central wavelength in the star's rest-frame. They all have symmetric shapes and are broadened with velocities from 30 to 100km/s. The only star of the sample with asymmetric, blueshifted forbidden lines is R Mon, which is believed to be surrounded by a circumstellar accretion disk. The observed forbidden-line profiles of all stars except R Mon are inconsistent with models similar to those proposed for the formation of forbidden lines in the stellar or disk winds of TTauri stars, involving an optically thick circumstellar disk hiding the receding hemisphere of the wind. Models assuming that the forbidden lines originate from a geometrically thin region near a circumstellar disk may be able to explain the observations. As another interpretation, we propose that the forbidden lines are formed in the outermost parts of a stellar wind. In the framework of this interpretation, the symmetrical shape of the forbidden-line profiles implies the absence of extended optically thick accretion disks around these stars.