Discovery of Very High Energy Gamma-Ray Emissions from the Low-luminosity AGN NGC 4278 by LHAASO

The first source catalog of Large High Altitude Air Shower Observatory reported the detection of a very-high-energy gamma ray source, 1LHAASO J1219+2915. In this paper a further detailed study of the spectral and temporal behavior of this point-like source have been carried. The best-fit position of the TeV source (RA=185.05^∘±0.04^∘, Dec=29.25^∘±0.03^∘) is compatible with NGC 4278 within ∼0.03 degree. Variation analysis shows an indication of the variability at a few months level in the TeV band, which is consistent with low frequency observations. Based on these observations, we report the detection of TeV γ-ray emissions from this low-luminosity AGN NGC 4278. The observations by LHAASO-WCDA during active period has a significance level of 8.8 σ with best-fit photon spectral index =2.56±0.14 and a flux f_1-10 TeV=(7.0±1.1_sta±0.35_syst)×10^-13 photons cm^-2 s^-1, or approximately 5% of the Crab Nebula. The discovery of VHE from NGC 4278 indicates that the compact, weak radio jet can efficiently accelerate particles and emit TeV photons.