We report the discovery of \gamma -ray emission from the Circinus galaxy using the Large Area Telescope ( LAT ) onboard the Fermi Gamma-ray Space Telescope .
Circinus is a nearby ( \sim 4 Mpc ) starburst with a heavily obscured Seyfert-type active nucleus , bipolar radio lobes perpendicular to the spiral disk , and kpc-scale jet-like structures .
Our analysis of 0.1–100 GeV events collected during 4 years of LAT observations reveals a significant ( \simeq 7.3 \sigma ) excess above the background .
We find no indications of variability or spatial extension beyond the LAT point-spread function .
A power-law model used to describe the 0.1 - 100 GeV \gamma -ray spectrum yields a flux of ( 18.8 \pm 5.8 ) \times 10 ^ { -9 } ph cm ^ { -2 } s ^ { -1 } and photon index 2.19 \pm 0.12 , corresponding to an isotropic \gamma -ray luminosity of 3 \times 10 ^ { 40 } erg s ^ { -1 } .
This observed \gamma -ray luminosity exceeds the luminosity expected from cosmic-ray interactions in the interstellar medium and inverse Compton radiation from the radio lobes .
Thus the origin of the GeV excess requires further investigation .