Stellar jets with intrinsically variable sources

Abstract

New observational evidence indicates that the sources of stellar jets might be intrinsically variable. In some cases, the radial velocity of the jets shows strong variations with position, which can be interpreted as evidence for a variable ejection velocity. Some jets show discontinuous jumps in the radial velocity (as a function of position along the jet) and also show two or more well-aligned bow shock-like structures. Such structures can be interpreted as evidence for multiple outflow episodes from the jet source. In this paper, we present simplified models for jets from sources with time-dependent velocities. We find that the relaxation of the assumption of a time-independent source (an assumption common to most of the jet models which have been previously calculated) allows us to explain in a very straightforward way the complex position-velocity diagrams and multiple bow shock structures observed in some stellar jets. We present both analytic and numerical models for jets with variable velocity sources. We carry out a comparison with previously published observations of the HH 46/47 jet which illustrates the very promising characteristics of these models. From this comparison, we show how the velocity variations observed along a jet can be used to reconstruct the past time variability of the source. This technique is potentially very interesting for future studies of the mechanism by which stellar jets are produced.