A molecular outflow traced by SiO masers in Orion KL

We present full-resolution (similar to 0.2 mas, similar to 0.1 AU) Very Lon g Baseline Interferometry maps of the v = 1, J = 1 --> 0 SiO masers in the Orion KL nebula. The morphology and turbulent nature of the maser emission argues against models in which the masers form in an expanding and rotating protostellar disk. Rather, we find that the symmetry evident in the SiO ma ser emission points toward its genesis in a bipolar outflow. Water masers t hat also appear toward Orion KL are known to share the velocity profile and double-peaked characteristics of the SiO maser emission yet form much fart her away from the protostar. We link the water masers to our present result s by proposing that both species of maser form around a flared molecular ou tflow of roughly constant velocity.