MOLECULAR OUTFLOWS FROM FU ORIONIS STARS

We have detected molecular outflows toward six out of eight FU Orionis stars that we observed in the J = 3 --> 2 line of CO. Notably, FU Ori onis itself does not show an outflow. Four of the souces were mapped, and two show evidence for multiple outflows. In both Z CMa and RNO 1b, nearby infrared sources may also be driving the outflows. Mass-loss r ates derived from the usual assumptions of momentum conservation range from 3 x 10(-8) M. yr-1 to 2 x 10(-6) M. yr-1 without corrections for optical depth in the CO lines. Corrections for optical depth raise th ese estimates by a factor of 5 on average. If the outflows are driven by repeated outbursts with peak mass-loss rates of 10(-5) M. yr-1, a d uty cycle of 10(-3) to 10(-1) would be implied, consistent with other recent evidence.