KNOTS IN STELLAR JETS FROM TIME-DEPENDENT SOURCES

We present an analytical model that describes the time-evolution of a highly supersonic jet of small opening angle ejected from a time-dependent source. With this model, we explore the possibility that the aligned knots observed along astrophysical (and in particular, stellar) jets might be the result of "internal working surfaces" produced in the jet flow as a result of a time-dependent ejection velocity. This model allows us to carry out very concrete predictions of the shock velocities, H-alpha luminosities and characteristic masses of the knots in a stellar jet. We present a comparison between these predictions and previously existing observations of the HH 34 outflow (which has a very well defined, jetlike structure), and find a surprisingly good agreement between theoretical predictions and observations.