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

Abstract

The γ-ray pulsar PSRB1706−44 and the adjacent supernova remnant (SNR) candidate G343.1−2.3 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 αJ2000 = 17h08m11s ± 17s and δJ2000 = −44◦20ʹ ± 4ʹ. 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 ± 0.1stat ± 0.2sys. 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 PSRB1706−44 and/or with the complex radio structure of the partial shell-type SNR G343.1−2.3.