Revisiting Gamma-Ray Emission of the Supernova Remnant RCW 103

We analyze more than 15 years of the data, obtained with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope (Fermi), for the region of the young supernova remnant (SNR) RCW 103, since the nearby source 4FGL J1616.2-5054e, counterpart to HESS J1616-518 and ≃13 arcmin away from the SNR, is determined to be extended in the more recent Fermi-LAT source catalog. Different templates for 4FGL J1616.2-5054e and RCW 103 are tested, and we find that a point source with a power-law (PL) spectrum at the southern limb of the SNR best describes the detected gamma-ray emission. The photon index of the PL emission is Γ≃ 2.31, softer than the previously reported Γ≃ 2.0 when the counterpart to HESS J1616-518 was considered to be a point source (which likely caused mis-identification of extended emission at RCW 103). In order to produce the emission in a hadronic scenario, we estimate that protons with an index∼2.4 PL energy distribution are needed. These results fit with those from multi-wavelength observations that have indicated the remnant at the southern limb is interacting with a molecular cloud.