  We investigate the plausibility of detecting X-ray emission from a stellar
jet that impacts against a dense molecular cloud. This scenario may be usual
for classical T Tauri stars with jets in dense star-forming complexes. We first
model the impact of a jet against a dense cloud by 2D axisymmetric hydrodynamic
simulations, exploring different configurations of the ambient environment.
Then, we compare our results with XMM-Newton observations of the Herbig-Haro
object HH 248, where extended X-ray emission aligned with the optical knots is
detected at the edge of the nearby IC 434 cloud. Our simulations show that a
jet can produce plasma with temperatures up to 10 MK, consistent with
production of X-ray emission, after impacting a dense cloud. We find that jets
denser than the ambient medium but less dense than the cloud produce detectable
X-ray emission only at the impact onto the cloud. From the exploration of the
model parameter space, we constrain the physical conditions (jet density and
velocity, cloud density) that reproduce well the intrinsic luminosity and
emission measure of the X-ray source possibly associated with HH 248. Thus, we
suggest that the extended X-ray source close to HH 248 corresponds to the jet
impacting on a dense cloud.
