Search

We report the observation of a very high energy а -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 σ = (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 0.9-50 TeV. The integral а -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. [ABSTRACT FROM AUTHOR]

The extended gamma-ray source MGRO J1908+06, discovered by the Milagro air shower detector in 2007, has been observed for ∼4 years by the ARGO-YBJ experiment at TeV energies, with a statistical significance of 6.2 standard deviations. The peak of the signal is found at a position consistent with the pulsar PSR J1907+0602. Parameterizing the source shape with a two-dimensional Gauss function, we estimate an extension of σext = 0.°49 ± 0.°22, which is consistent with a previous measurement by the Cherenkov Array H.E.S.S. The observed energy spectrum is dN/dE = 6.1 ± 1.4 × 10–13 (E/4 TeV)–2.54 ± 0.36 photons cm–2 s–1 TeV–1, in the energy range of ∼1-20 TeV. The measured gamma-ray flux is consistent with the results of the Milagro detector, but is ∼2-3 times larger than the flux previously derived by H.E.S.S. at energies of a few TeV. The continuity of the Milagro and ARGO-YBJ observations and the stable excess rate observed by ARGO-YBJ and recorded in four years of data support the identification of MGRO J1908+06 as the steady powerful TeV pulsar wind nebula of PSR J1907+0602, with an integrated luminosity over 1 TeV ∼ 1.8 times the luminosity of the Crab Nebula. [ABSTRACT FROM AUTHOR]