Globular clusters (GCs) are established emitters of high-energy (HE, 100 MeV<E<100 GeV) gamma-ray radiation which could originate from the cumulative emission of the numerous millisecond pulsars (msPSRs) in the clusters cores or from inverse Compton
(IC) scattering of relativistic leptons accelerated in the GC environment. GCs could also constitute a new class of sources in the very-high-energy (VHE, E>100 GeV) gamma-ray regime, judging from the recent detection of emission from the direction of Terzan 5 with the H.E.S.S. telescope array. To search for VHE gamma-ray sources associated with other GCs, and to put constraints on leptonic emission models, we systematically analyzed the observations towards 15 GCs taken with H.E.S.S. We searched for individual sources of VHE gamma-rays from each GC in our sample and also performed a stacking analysis combining the data from all GCs to investigate the hypothesis of a population of faint emitters. Assuming IC emission as the source of emission from Terzan 5, we calculated the expected gamma-ray flux for each of the 15 GCs, based on their number of millisecond pulsars, their optical brightness and the energy density of background photon fields. We did not detect significant emission from any of the 15 GCs. The obtained flux upper limits allow to rule out the simple IC/msPSR scaling model for NGC 6388 and NGC 7078. The upper limits derived from the stacking analyses are factors between 2 and 50 below the flux predicted by the simple leptonic model, depending on the assumed source extent and the dominant target photon fields. Therefore, Terzan 5 still remains exceptional among all GCs, as the VHE gamma-ray emission either arises from extra-ordinarily efficient leptonic processes, or from a recent catastrophic event, or is even unrelated to the GC itself.
Observations by the H.E.S.S. system of imaging atmospheric Cherenkov telescopes provide the most sensitive measurements of the Galactic Centre region in the energy range 150 GeV - 30 TeV. The vicinity of the kinetic centre of our galaxy harbours nume
rous objects which could potentially accelerate particles to very high energies (VHE, > 100 GeV) and thus produce the Gamma-ray flux observed. Within statistical and systematic errors, the centroid of the point-like emission measured by H.E.S.S. was found to be in good agreement with the position of the supermassive black hole Sgr A* and the recently discovered PWN candidate G359.95-0.04. Given a systematic pointing error of about 30, a possible association with the SNR Sgr A East could not be ruled out with the 2004 H.E.S.S. data. In this contribution an update is given on the position of the H.E.S.S. Galactic Centre source using 2005/2006 data. The systematic pointing error is reduced to 6 per axis using guiding telescopes for pointing corrections, making it possible to exclude with high significance Sgr A East as the source of the VHE Gamma-Rays.
