The precessing jets of SS433

W. Brinkmann (with E. Müller, MPA and N. Kawai, T.Kotani, RIKEN, Japan)

The peculiar galactic object SS433, detected almost two decades ago, is still the only galactic source with a jet which can be studied over all frequencies, from the radio to the X-ray band. The central object of the supernova remnant W 50 is a binary system in which the compact object emits two oppositely directed jets of 'normal' matter flowing out with relativistic velocities, precessing with a period of ~ 163 days at an angle of 19.8o.

X-ray observations were able to narrow down the physical parameters of the out-flowing jets with errors of order unity and recent ASCA observations with the high spectral resolution of CCD detectors could be used for plasma diagnostics via emission lines. To study model-dependent details of the emitting plasma we have performed 2-D hydrodynamic simulations of the inner jet including photo ionization and non-equilibrium ionization calculations.

In ROSAT observations the interaction of the jets with the surrounding interstellar medium on larger spatial scales could be studied. The X-ray observations showed unexpected results: the emitted spectrum seems to be non-thermal and the opening angle of the X-ray emitting volume is much smaller than the precession angle of the jets.

To understand the dynamics and the interaction of these jets with the surrounding medium, the temporal evolution of astrophysical jets was calculated for the first time with an explicit 3-dimensional hydrodynamic simulation. The parameters used in the calculations correspond to those deduced for SS433 from observations. The figure shows a jet after it evolved for six precessional periods. Plotted is the three dimensional surface of the computational volumes which contain more than 60% of the original jet material. Close to the origin the jet has its undisturbed original shape, but fairly soon it is heavily disrupted through its strong, complex interaction with the circumstellar medium.

Although the computer simulations have so far not been performed up to the evolutionary age of the real jets, it is nevertheless indicated that the numerically deduced physical properties seem to be able to explain the observational results quite naturally.


Brinkmann W., Aschenbach B., & Kawai N: ROSAT observations of the W50/SS433 system, A&A 312, 306, 1996
Kotani T., Kawai N., Matsuoka M, & Brinkmann W.: Iron-line diagnostics of the jets of SS433, PASJ 48, 619, 1996

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