First Detection of $\gamma$-Ray Emission from the Compact Symmetric Object JVAS J1311+1658

We report the first detection of $\gamma$-ray emission from the young radio galaxy JVAS~J1311+1658, classified as a compact symmetric object (CSO). This detection is characterized by a recent GeV $\gamma$-ray flare identified in Fermi-LAT data during MJD~60032.6–60132.6, with a $\gamma$-ray source detected at a significance level of $\sim 6.2\sigma$. The average 0.1–300~GeV flux is measured to be $(1.6\pm 0.6)\times {10}^{-8}\mathrm{p}\mathrm{h}\mathrm{c}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$, with a photon spectral index of $\mathrm{\Gamma }=2.15\pm 0.185$. We find that a radiative model of the radio lobes significantly underestimates the observed $\gamma$-ray emission. The strong flux and short-term variability over $\sim$100 days suggest that the emission likely originates from newly launched sub-kiloparsec-scale jets at the core. This detection provides a unique window into the extreme environments and early-stage jet activity of young radio galaxies, offering insights into their initial evolution and the formation of relativistic jets in the earliest phases of galaxy growth.