Testing the Origin of Excess Gamma Rays Coinciding with 3FHL J1907.0+0713

We used the off-pulse component of 9 years of Fermi-LAT data taken from the pulsar, PSR J1906+0722, and found excess gamma rays located 0.12 deg away from the supernova remnant (SNR) 3C 397 and 0.27 deg away from the pulsar. The position of this excess emission coincides with the gamma-ray source 3FHL J1907.0+0713. The 3FHL source also overlaps with a dense molecular cloud (MC), which raises the question whether the gamma-ray emission could be due to the interaction of very high energy particles escaping from either the SNR or a possible pulsar wind nebula (PWN) associated with PSR J1906+0722. The distance of the MC is either 10.7 kpc, therefore, close to the SNR, or 2.1 kpc, in the vicinity of the pulsar. The gamma-ray spectrum is probed for the leptonic model and two hadronic models, the interacting cloud scenario and the illuminating cloud scenario, in order to understand the dominant gamma-ray emission model. The results of this analysis may reveal the existence of a PWN for PSR J1906+0722, in case leptonic model dominates. Alternatively, when the hadronic model dominates, we might be able to differentiate between the two models within the hadronic scenario.