HESS J1832$-$085: evidence for a new gamma-ray binary candidate

Abstract

The Galactic plane survey conducted by the High Energy Stereoscopic System (H.E.S.S.) has revealed numerous teraelectronvolt (TeV) sources, many of which remain unidentified. HESS~J1832$-$085 is a point-like TeV source lacking a confirmed multiwavelength (MWL) counterpart. In this paper, we present evidence that HESS~J1832$-$085 is likely a gamma-ray binary. We aim to investigate the nature of HESS~J1832$-$085 using {\it Fermi}-LAT and X-ray data, complemented by broadband radiative modeling, to assess its classification as a potential gamma-ray binary. We analyzed $\sim$17.3~yr of {\it Fermi}-LAT data between 0.1 and 500~GeV to establish the gigaelectronvolt (GeV) counterpart of HESS~J1832$-$085, including performing spectral, spatial, and periodicity analyses. Archival X-ray observations were examined to search for a counterpart and to characterize its spectrum and potential variability. The broadband emission was interpreted using models commonly applied to gamma-ray binaries. We detect a point-like GeV gamma-ray source spatially consistent with HESS~J1832$-$085, with spectral properties compatible with known gamma-ray binaries. No significant GeV periodic modulation is detected. A potential X-ray counterpart is identified in archival X-ray data, exhibiting a hard, absorbed spectrum and moderate variability. The broadband spectral energy distribution is reproduced by the adopted binary radiative model. Our results indicate that HESS~J1832$-$085 is likely a gamma-ray binary candidate, motivating dedicated MWL follow-up observations to confirm the source nature.