2006A&A...448L..29G

We report the detection during the Chandra Orion Ultradeep Project (COUP) of two soft, constant, and faint X-ray sources associated with the Herbig-Haro object HH210. HH210 is located at the tip of the NNE finger of the emission line system bursting out of the BN-KL complex, northwest of the Trapezium cluster in the OMC-1 molecular cloud. Using a recent Hα image obtained with the ACS imager on board HST, and taking into account the known proper motions of HH210 emission knots, we show that the position of the brightest X-ray source, COUP703, coincides with the emission knot 154-040a of HH210, which is the emission knot of HH210 having the highest tangential velocity (425km/s). The second X-ray source, COUP704, is located on the complicated emission tail of HH210 close to an emission line filament and has no obvious optical/infrared counterpart. Spectral fitting indicates for both sources a plasma temperature of ∼0.8MK and absorption-corrected X-ray luminosities of about 10³⁰erg/s (0.5-2.0keV). These X-ray sources are well explained by a model invoking a fast-moving, radiative bow shock in a neutral medium with a density of ∼12000cm^–3. The X-ray detection of COUP704 therefore reveals, in the complicated HH210 region, an energetic shock not yet identified at other wavelengths.