Hans Moritz Günther edited abstract.tex  almost 10 years ago

Commit id: b2a67203bbe90d36274dac865f49dd84bfb020a7

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All Young stars accrete mass fomr circumstellar disks. In many cases, the accretions coincides with a phase of massive outflows, which can be highly collimated. Those  jets from pre-main-sequence stars emit predominantly  in the optical and IR wavelength range. However, in several cases X-ray and UV observations reveal a weak but highly energetic component in those jets. If this component is heated in shocks then the required velocities X-rays  are $>$300~km~s$^{-1}$ for standing shocks observed both from stationary regions close to the star  and higher for moving shock fronts. from knots in the jet several hundred AU from the star.  In this article we show semi-analytically that a fast, stellar wind which is recollimated by the pressure from a slower, more massive disk wind can have the right properties to explain the observed power stationary  X-ray emission. The size of the shock regions is compatible with the observational contraints. constraints.  Our calculations support a wind-wind interaction scenario for the high energy emission near the base of YSO jets. For the specific case of DG~Tau, a stellar wind with a mass loss rate of $5\cdot10^{-10}\;M_{\odot}\mathrm{ yr}^{-1}$ and a wind speed of 800~km~s$^{-1}$ reproduces the observed X-ray spectrum. We conclude that stellar wind recollimation shocks are one possible scenario to power stationary X-ray emission close to the jet launching point.