Radio Emission from the Bow Shock of G2
  The radio flux from the synchrotron emission of electrons accelerated in the
forward bow shock of G2 is expected to have peaked when the forward shock
passes close to the pericenter from the Galactic Center, around autumn of 2013.
This radio flux is model dependent. We find that if G2 were to be a
momentum-supported bow shock of a faint star with a strong wind, the radio
synchrotron flux from the forward-shock heated ISM is well below the quiescent
radio flux of Sgr A*. By contrast, if G2 is a diffuse cloud, the radio flux is
predicted to be much larger than the quiescent radio flux and therefore should
have already been detected or will be detected shortly. No such radiation has
been observed to date. Radio measurements can reveal the nature of G2 well
before G2 completes its periapsis passage.
