High-energy gamma-ray emission powered by a young protostar: the case of S255 NIRS 3

Abstract

ABSTRACT Evidence of efficient acceleration of cosmic rays in massive young stellar objects has been recently reported. Among these massive protostars, S255 NIRS 3, for which extreme flaring events associated with radio jets have been detected, is one of the best objects to test this hypothesis. We search for gamma-ray emission associated with this object in Fermi-LAT data and inspect the gas content in different molecular lines using the MWISP survey. A GeV source dubbed 4FGL J0613.1+1749c lies on top of the MYSO region, where two filamentary ∼10 pc CO structures extend along the same direction of the subparsec radio jets. We investigate the spectrum, morphology, and light curve of the gamma-ray source and compare it with the theoretical emission expected from hadronic and leptonic populations accelerated in the radio jets. We argue that the gamma-ray source could be powered by particles accelerated in the S255 NIRS 3 jets, radiating via bremsstrahlung or proton–proton interaction, and with a synchrotron component shinning in radio from primary or secondary electrons in the case of a leptonic or hadronic population.