  We have observed a bright flare of Sgr A* in the near infrared with the
adaptive optics assisted integral field spectrometer SINFON. Within the
uncertainties, the observed spectrum is featureless and can be described by a
power law. Our data suggest that the spectral index is correlated with the
instantaneous flux and that both quantities experience significant changes
within less than one hour. We argue that the near infrared flares from Sgr A*
are due to synchrotron emission of transiently heated electrons, the emission
being affected by orbital dynamics and synchrotron cooling, both acting on
timescales of ~20 minutes.
