G5.89: An Explosive Outflow Powered by a Proto-Stellar Merger?
  The explosive outflows are a newly-discovered family of molecular outflows
associated with high-mass star forming regions. Such energetic events are
possibly powered by the release of gravitational energy related with the
formation of a (proto)stellar merger or a close stellar binary. Here, we
present sensitive and high angular resolution observations (0.85$''$) archival
CO(J=3-2) observations carried out with the Submillimeter Array (SMA) of the
high-mass star forming region G5.89$-$0.39 that reveal the possible presence of
an explosive outflow. We find six well-defined and narrow straight
filament-like ejections pointing back approximately to the center of an
expanding molecular and ionized shell located at the center of this region.
These high velocity ($-$120 to $+$100 km s$^{-1}$) filaments follow a
Hubble-like velocity law with the radial velocities increasing with the
projected distance. The estimated kinematical age of the filaments is about of
1000 yrs, a value similar to the dynamical age found for the expanding ionized
shell. G5.89 is the thus the third explosive outflow reported in the galaxy
(together with Orion BN-KL and DR21) and argues in favor of the idea that this
is a frequent phenomenon. In particular, explosive outflows, in conjunction
with runaway stars, demonstrate that dynamical interactions in such groups are
a very important ingredient in star formation.
