Narrow Results

H.E.S.S., a system of imaging Cherenkov telescopes, is dedicated to the observation of TeV gamma-rays. Within the first years of operation a number of objects were detected, most of these objects were previously not known to be TeV emitters. The observed TeV emission is crucial for the understanding of particle acceleration in the sources.

Here I will review the results obtained on Galactic sources expected to show variable emission. Variable emission was detected with high significance from the binary systems PSR B1259−63 / SS 2883 and LS5039. The emission of the latter object appears to be periodic in accordance with the orbit. No pulsed emission from pulsars was detected so far. For three pulsars (PSR B0531+21, PSR B0833−45, PSR B1706−44) upper limits on the TeV emission at the EGRET pulse phases were derived.

The diffuse gamma radiation arising from the interaction of cosmic ray particles with matter and radiation in the Galaxy is one of the few probes available to study the origin of the cosmic rays. Milagro is a water Cherenkov detector that continuously views the entire overhead sky. The large field-of-view combined with the long observation time makes Milagro the most sensitive instrument available for the study of large, low surface brightness sources such as the diffuse gamma radiation arising from interactions of cosmic radiation with interstellar matter. In this paper we report our results on diffuse emission from the galactic plane and in particular the Cygnus region. Our observations show at least one new TeV source MGRO J2020+37 as well as correlations with the matter density in the region as would be expected from cosmic-ray proton interactions. However, the TeV gamma-ray flux from the Cygnus region (after excluding MGRO J2020+37) is roughly 5 times that expected from a conventional model of cosmic ray production and propagation.