Gamma-ray and X-ray view of N 157B. a) Image of the TeV gamma-ray excess obtained with H.E.S.S. The image was smoothed with the instrument’s point-spread function, which is shown in the inset. The green contour lines denote 6, 9, and 12σ statistical significances. The black box outlines the region shown in the X-ray image. b) Image of the X-ray flux in the energy band from 0.8 keV to 8 keV (Chandra ACIS-S, observation n^o. 2783, 48.2 ks dead-time corrected exposure). The data were smoothed with a Gaussian of σ = 1.5″ and the exposure map was computed with an assumed spectral index of 2.3, which is the average index of the nebula. The colour coding represents the X-ray flux in photons cm^-2 s ^-1; for better visibility, it is clipped at 10^-13 photons cm^-2 s^-1 at the lower end and saturates at 10^-5 photons cm^-2 s^-1. The white contour lines denote regions of 68%, 95%, and 99% confidence for the position of the gamma-ray source HESS J0537 − 691. The position of the pulsar PSR J0537 − 6910 is indicated by a black cross. The green cross marks the best-fit position and the systematic uncertainty in the pointing of the H.E.S.S. telescopes.