Detection of very-high-energy γ-ray emission from the vicinity of PSR B1706–44 and G 343.1–2.3 with H.E.S.S.

The γ-ray pulsar PSR B1706−44 and the adjacent supernova remnant (SNR) candidate G 343.1−2.3 were observed by H.E.S.S. during a dedicated observation campaign in 2007. As a result of this observation campaign, a new source of very-high-energy (VHE; E > 100 GeV) γ-ray emission, H.E.S.S. J1708−443, was detected with a statistical significance of 7σ, although no significant point-like emission was detected at the position of the energetic pulsar itself. In this paper, the morphological and spectral analyses of the newly-discovered TeV source are presented. The centroid of H.E.S.S. J1708−443 is considerably offset from the pulsar and located near the apparent center of the SNR, at α_J2000 = 17^h08^m11^s ± 17^s and δ_J2000 =  −44°20′ ± 4′. The source is found to be significantly more extended than the H.E.S.S. point spread function (~0.1°), with an intrinsic Gaussian width of 0.29°  ±  0.04°. Its integral flux between 1 and 10 TeV is  ~ 3.8 × 10^-12   ph   cm^-2   s^-1, equivalent to 17% of the Crab Nebula flux in the same energy range. The measured energy spectrum is well-fit by a power law with a relatively hard photon index Γ = 2.0  ±  0.1_stat  ±  0.2_sys. Additional multi-wavelength data, including 330 MHz VLA observations, were used to investigate the VHE γ-ray source’s possible associations with the pulsar wind nebula of PSR B1706−44 and/or with the complex radio structure of the partial shell-type SNR G 343.1−2.3.