Fermi Gamma-ray Space Telescope

Fermi-LAT upper limit for NGC 4151 and its theoretical implication

Rafal Wojaczynski
R. Wojaczynski, A. Niedzwiecki

Abstract:

We present preliminary results of our analysis of the Fermi-LAT data from the direction of NGC 4151. We find a new gamma-ray source, with TS=25, shifted by $sim 1$ degree from NGC 4151. We derive a refined value of the upper limit for the gamma-ray flux from NGC 4151 and we compare it with predictions of the ADAF model which can explain the X-ray observations of this object. We find that the energy content in the non-thermal component of proton distribution is limited to at most a few per cent. Then, the Fermi-LAT upper limit strongly constrains non-thermal acceleration processes in hot flows.