Abstract Based on 17 yr of Fermi-LAT observations in the energy range from 5 GeV to 1 TeV, we have detected GeV gamma-ray emission that is spatially correlated with the unidentified very-high-energy (VHE; >100 GeV) gamma-ray source HESS J1708-410. The GeV emission exhibits a mildly extended morphology, and its spectrum is best described by a power-law model with a photon index of 1.76 ± 0.12 from 300 MeV to 1 TeV. High-resolution CO observations reveal multiple molecular cloud clumps within the gamma-ray emission region. Both leptonic and hybrid models can well explain the multiwavelength data of HESS J1708-410 with the different ambient gas densities, though each imposes distinct constraints on the magnetic field strength in the emission region. The possible physical origins for HESS J1708−410 are discussed, including supernova remnant, pulsar wind nebula, and pulsar halo, though the lack of detected expanding shells or pulsars challenges these scenarios.
Guo et al. (Wed,) studied this question.