A&A 450, 645-654 (2006)
DOI: 10.1051/0004-6361:20054089

Hydrodynamical simulations of the jet in the symbiotic star MWC 560

II. Simulations beyond density balance

M. Stute

Landessternwarte Heidelberg, Königstuhl, 69117 Heidelberg, Germany
    e-mail: Matthias.Stute@jpl.nasa.gov

(Received 23 August 2005 / Accepted 19 December 2005)

Abstract
Context.In the first paper of this series, we presented hydrodynamical simulations with radiative cooling of jet models with parameters representative of the symbiotic system MWC 560. These were jet simulations of a pulsed, initially underdense jet in a high-density ambient medium. They were stopped when the jet reached a length of 50 AU. There, however, a transition of the initially underdense jet towards an overdense jet should occur, which should result in changed kinematics. A few minor differences between the models and the observations were thought to be solved by a model with an increased jet density during the pulses which was calculated only with purely hydrodynamical means in the former paper.
Aims.Therefore, we describe two hydrodynamical simulations with cooling beyond this density balance, one with the same parameters as model i in Paper I (now called model i´), which was presented there with and without cooling, and the second with higher gas densities in the jet pulses (model iv´).
Methods.Hydrodynamical simulations, with a further approximated cooling treatment compared to Paper I, were used to be able to enlarge the computational domain.
Results.The transition causes changes in the expansion of the cocoon and therefore the morphology of the jet, e.g. a larger radial width of the jet knots. We investigate the radiation properties of the jets, the bremsstrahlung and optical emissivities, integrated emission maps, and synthetic absorption line profiles.
Conclusions.The conclusion that the high observed velocities in CH Cygni, R Aquarii, and MWC 560 favor the models with cooling is unchanged by the transition. The observed parallel features in R Aquarii can be produced by the internal knots or by a variable dense radiative shell of shocked ambient medium. The absorption line profiles show that the real parameters in MWC 560 are closer to model iv´ than to model i´.

Key words: ISM: jets and outflows -- binaries: symbiotic -- line: profiles -- hydrodynamics -- methods: numerical

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