19 D ec 2 01 6 Modeling the gamma-ray emission in the Galactic Center witha fading cosmic-ray accelerator

Recent HESS observations of the ∼ 200 pc scale diffuse gamma-ray emission from the central molecular zone (CMZ) suggest the presence of a PeV co smi -ray accelerator (PeVatron) located in the inner 10 pc region of the Galactic Center. Inte restingly, the gamma-ray spectrum of the point-like source (HESS J1745-290) in the Galactic Ce nter shows a cutoff at ∼ 10 TeV, implying a cutoff around 100 TeV in the cosmic-ray proton spe ctrum. Here we propose that the gamma-ray emission from the inner and the outer regions may b e explained self-consistently by run-away protons from a single, yet fading accelerator. I n this model, gamma rays from the CMZ region are produced by protons injected in the past, whil e gamma rays from the inner region are produced by protons injected more recently. We su ggest that the blast wave formed in a tidal disruption event (TDE) caused by the supermassive black hole (Sgr A*) could serve as such a fading accelerator. With typical parameters of the TD E blast wave, gamma-ray spectra of both the CMZ region and HESS J1745-290 can be reproduced si multaneously. Meanwhile, we find that the cosmic-ray energy density profile in the CMZ re gion may also be reproduced in the fading accelerator model when appropriate combinati o s of the particle injection history and the diffusion coefficient of cosmic rays are adopted.