Discovery of a new type of very-high-energy gamma ray emitter

Left side: H.E.S.S. gamma-ray sky map of the Westerlund 2 region, smoothed to reduce the effect of statistical fluctuations. The inlay in the lower left corner shows how a point-like source would have been seen by H.E.S.S. The WR stars WR 20a and WR 20b are marked as filled triangles, and the stellar cluster Westerlund 2 is represented by a dashed circle. Right side: Significance contours of the gamma-ray source HESSJ1023-575 (corresponding 5, 7 and 9 sigma), overlaid on a radio image from the Molonglo Observatory Synthesis Telescope (MOST). The wind-blown bubble around WR 20a, and the blister to the west of it can be seen as depressions in the radio continuum map. The blister is indicated by white dots as in Whiteoak and Uchida (1997), and appears to be compatible in direction and location with HESSJ1023-575. Credit: HESS