Observation of tev gamma rays from the unidentified source hess J1841-055 with the ARGO-YBJ Experiment

Abstract

We report the observation of a very high energy γ-ray source whose position is coincident with HESS J1841?055. This source has been observed for 4.5 years by the ARGO-YBJ experiment from 2007 November to 2012 July. Its emission is detected with a statistical significance of 5.3 standard deviations. Parameterizing the source shape with a two-dimensional Gaussian function, we estimate an extension δ= (0.40+0.32?0.22)°, which is consistent with the HESS measurement. The observed energy spectrum is dN/dE = (9.0±1.6) ?10?13(E/5 TeV)?2.32± 0.23 photons cm?2 s?1 TeV?1, in the energy range 0.950 TeV. The integral ? -ray flux above 1 TeV is 1.3±0.4 Crab, which is 3.2±1.0 times the flux derived by HESS. The differences in the flux determination between HESS and ARGO-YBJ and possible counterparts at other wavelengths are discussed. © 2013. The American Astronomical Society. All rights reserved.