Hans Moritz Günther edited Results.tex  about 10 years ago

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\left(\frac{10^5\mathrm{ cm}^{-3}}{n_0}\right)  \left(\frac{v_{\mathrm{shock}}}{500\mathrm{ km s}^{-1}}\right)^{4.5}\ .  \end{equation}  The derivation for this formula assumes a cylindrical cooling flow. In contrast, in our model the external pressure will continue to compress the gas, as it starts cooling. Since denser gas emits more radiation and thus cools faster, $d_{\mathrm{cool}}$ is only an upper limit. With this in mind, figure~\ref{fig:rhocool} (lower panel) indicates that the cooling lengths for our fiducial model is consistent with the X-ray observations that do not resolve the wind shock \citep{2008A&A...488L..13S}.On the other hand, a model with a wind mass loss rate of only $10^{-10}$~M$_{\odot}$~yr$^{-1}$ violates the observational constraints.  Since only a very small fraction of the stellar mass loss is heated to X-ray emitting temperatures (Fig.~\ref{fig:result}, rightmost panel) the low-mass loss scenario also does not provide enough X-ray luminosity to explain the observations (paper~I). Significantly higher pressures require unrealistically fast outflows to push the shock front out to 40~AU and lower pressures do not allow a mass flux high enough to power the X-ray luminosity.  In our model, it is irrelevant how much of the external pressure is provided by the magnetic field in the disk wind and how much by thermodynamic pressure. The region of interest is still within the Alfv\'en surface (see references in Sect.~\ref{sect:boundary}), so the influence of the magnetic field probably dominates. Otherwise, the disk wind would also have to be very dense (probably too dense to be consistent with observations) to provide this pressure. Observationally, it is difficult to distinguish the stellar wind from the disk wind. The slower jet components observed further away from the jet axis carry much of the mass flow \citep{2000ApJ...537L..49B}. Their origin is probably the inner region of the disk and not the star \citep{2003ApJ...590L.107A}. Thus, it is fully consistent that our model predicts a mass loss fraction larger than $10^{-3}$ of the stellar wind at X-ray emitting temperatures. If the disk wind dominates over the stellar wind in mass loss, then the fraction of hot gas in the (stellar plus inner disk) jet might still be small.