High Energy Gamma Rays

The Very High Energy Gamma Ray Astronomy (VHE) is a rapidly evolving branch of modern astronomy, which covers the range from about 50 GeV to several tens of TeV from the ground. In the past years, the second generation instruments firmly established a growing and varied list of sources including plerions, supernova remnants and active galactic nuclei, and started to study some fundamental questions such as the origin of cosmic rays or the emission mechanisms of the active galactic nuclei. New results now include the first VHE unidentified sources as well as more puzzling sources such as the Galactic center. The arrival of new generation instruments (HESS, CANGAROO III, VERITAS, MAGIC) already gives a impressive look at the near future. Here we attempt to summarize the current status of the field. We briefly describe the instruments and analysis techniques, and give an outlook on the sources detected sofar.Comment: Invited talk at the XXIV Physics in Collisions Conference (PIC04), Boston, USA, June 2004, 10 pages, LaTeX, 13 eps figures. PSN TUET0

Analysis methods for Atmospheric Cerenkov Telescopes

Three different analysis techniques for Atmospheric Imaging System are presented. The classical Hillas parameters based technique is shown to be robust and efficient, but more elaborate techniques can improve the sensitivity of the analysis. A comparison of the different analysis techniques shows that they use different information for gamma-hadron separation, and that it is possible to combine their qualities

Observation of the microquasar LS 5039 with H.E.S.S.

texte intégral disponible sur http://proc.sf2a.asso.fr/2006/2006sf2a.conf..0125D.pdfInternational audienceThe High Energy Stereoscopic System (H.E.S.S) is an array of four imaging atmospheric-Cherenkov telescopes located in the Khomas Highlands of Namibia. The microquasar LS 5039 was serendipously detected by the instrument during the scan of the inner galactic plane in 2004. Deeper observation were carried out in 2005, and brought a clear evidence for TeV emission variability. This is after PSRB 1259-63 the second VHE gamma-rays variable galactic source discovered. We will present detailed studies of the source variability (flux and spectral shape) compared to other wavelengthes and shortly review the implications for the existing emission models

Utilisation de la grille EGI pour l'astrophysique de très hautes énergies avec H.E.S.S.

Utilisation de la grille EGI pour l'astrophysique de très hautes énergies avec H.E.S.S

Exploiting the time of arrival of Cherenkov photons at the 28 m H.E.S.S. telescope for background rejection: Methods and performance

In 2012, the High Energy Stereoscopic System (H.E.S.S.) was expanded by a fifth telescope (CT5). With an effective mirror diameter of 28m, CT5 is able to detect the Cherenkov light of very faint gamma-ray air showers, thereby significantly lowering the energy threshold of this telescope compared to the other four telescopes. Extracting as much information as possible from the recorded shower image is crucial for background rejection and to reach an energy threshold of a few tens of GeV. The camera of CT5 is conceived to register the time of the charge pulse maximum with respect to the beginning of the 16 ns integration window of each pixel. This information can be utilised to improve the event reconstruction. It also helps to reduce the background contamination at low energies. We present new techniques for background rejection based on CT5 timing information and evaluate their performance

The Galactic Sky seen by H.E.S.S

The H.E.S.S. experiment is an array of four imaging Cherenkov telescopes located in the Khomas Highlands of Namibia. It has been operating in its full configuration since December 2003 and detects very-high-energy (VHE) gamma rays ranging from 100 GeV to 50 TeV. Since 2004, the continuous observation of the Galactic Plane by the H.E.S.S. array of telescopes has yielded the discovery of more than 50 sources, belonging to the classes of pulsar wind nebulae (PWN), supernova remnants (SNR), gamma ray binaries and, more recently, a stellar cluster and molecular clouds in the vicinity of shell-type SNRs. Galactic emission seen by H.E.S.S. and its implications for particle acceleration in our Galaxy are discussed.Comment: Proceedings of COSPAR 2010 conference. Accepted for publication in Advances in Space Research (special issue

Briefing Book for the Zeuthen Workshop

On Jun 18th 2004, the CERN Council, upon the initiative of its President, Prof. Enzo Iarocci, established an ad hoc scientific advisory group (the Strategy Group), to produce a draft strategy for European particle physics, which is to be considered by a special meeting of the CERN Council, to be held in Lisbon on Jul 14th 2006. There are three volumes to the Briefing Book. This first volume contains an introductory essay on particle physics, a summary of the issues discussed at the Open Symposium, and discussions of the other themes that the Strategy should address. The introductory essay on particle physics and the other themes were commissioned by the Preparatory Group. The summary of the issues discussed in the Symposium was prepared by the chairs of the sessions, the session speakers and the scientific secretaries. We acknowledge that this has been a difficult task, again on a very tight timescale, and we would like to thank all of those who have contributed to this volume