Concurrent X-ray, near-infrared, sub-millimeter, and GeV gamma-ray observations of Sagittarius A*

Aims. The radiative counterpart of the supermassive black hole at the Galactic center (GC), Sgr A⋆, is subject to frequent flares that are visible simultaneously in X-rays and the near-infrared (NIR). Often, enhanced radio variability from centimeter to sub-millimeter wavelengths is observed to follow these X-ray/NIR eruptions. We present here a multi-wavelength campaign carried out in April 2009, with the aim of characterizing this broadband flaring activity.