Binary energy source of the HH 250 outflow and its circumstellar
  environment
  Herbig-Haro flows are signposts of recent major accretion and outflow
episodes. We aim to determine the nature and properties of the little-known
outflow source HH 250-IRS, which is embedded in the Aquila clouds. We have
obtained adaptive optics-assisted L-band images with the NACO instrument on the
Very Large Telescope (VLT), together with N- and Q-band imaging with VISIR also
on the VLT. Using the SINFONI instrument on the VLT we carried out H- and
K-band integral field spectroscopy of HH 250-IRS, complemented with spectra
obtained with the SpeX instrument at the InfraRed Telescope Facility (IRTF) in
the JHKL bands. Finally, the SubMillimeter Array (SMA) interferometer was used
to study the circumstellar environment of HH 250-IRS at 225 and 351 GHz with CO
(2-1) and CO (3-2) maps and 0.9 mm and 1.3 mm continuum images. The HH 250-IRS
source is resolved into a binary with 0''53 separation, corresponding to 120 AU
at the adopted distance of 225 pc. The individual components show heavily
veiled spectra with weak CO absorption indicative of late-type stars. Both are
Class I sources, but their spectral energy distributions between 1.5 $\mu$m and
19 $\mu$m differ markedly and suggest the existence of a large cavity around
one of the components. The millimeter interferometric observations indicate
that the gas mainly traces a circumbinary envelope or disk, while the dust
emission is dominated by one of the circumstellar envelopes. HH 250-IRS is a
new addition to the handful of multiple systems where the individual stellar
components, the circumstellar disks and a circumbinary disk can be studied in
detail, and a rare case among those systems in which a Herbig-Haro flow is
present.
