The Fermi Galactic Center excess as a signal from Bursts of Cosmic-Rays

The possible gamma-ray excess in the inner Galaxy and the Galactic center suggested by Fermi-LAT observations has triggered great interest in the astro-particle physics community. Among its various interpretations have been WIMP dark matter annihilations, gamma-ray emission from a population of millisecond pulsars, or emission from cosmic rays injected in a sequence of burst-like events or continuously at the Galactic Center. Accounting for the model systematics coming from the Galactic diffuse emission in the inner part of our Galaxy, we will present a comprehensive study of the latter possibility. A small series of outbursts, which took place approximately a million years ago, and 100s of thousands years ago and more recently can account for the observed gamma-ray signal. Furthermore strong re-acceleration and rapid synchrotron cooling conditions within the inner tens of pc of the Galaxy, could explain the hard spectrum of the observed gamma-ray excess. In fact, a connection to the Fermi Bubbles can be made.