$\gamma$-ray detection from occasional flares in T Tauri stars of NGC 2071. I. Observational connection

Abstract

NGC 2071 is a star-forming region that overlaps with three $\gamma$-ray sources detected by the Fermi Space Telescope. We propose that strong flare activity in T Tauri stars could produce $\gamma$-ray emission in a way that makes them a counterpart to some unidentified sources detected by the Large Area Telescope aboard the Fermi satellite. We have performed a spectral and temporal analysis for two Fermi data sets: the first 2 yr and the entire 14 yr of observations. We have found that the $\gamma$-ray source is detectable at 3.2$\sigma$ above the background at energies above 100 GeV during the first 2 yr of observation. The analysis of the expected frequency of the highest energy flares occurring in T Tauri stars is consistent with our estimate. In addition, we have determined the minimum energy of the flare that would produce $\gamma$-ray emission, which is $\sim 5 \times 10^{37}$ erg. This agreement becomes a hard observational constraint supporting previous hypotheses about rare flares as the origin of unidentified $\gamma$-ray sources in star-forming regions.