Very-High Energy Gamma-Ray Flux Limits for Nearby Active Galactic Nuclei

Combining the results of targeted observations, H.E.S.S. has accumulated a large amount of extra-galactic exposure at TeV energies. Due to its large field of view a considerable part of the sky (0.6 sr) has been observed with high sensitivity outside the targeted observation positions. Since this exposure region contains little inherent bias, it is well suited for studies of extra-galactic source populations. Given the correlation between ultra-high energy cosmic rays and nearby extra-galactic objects recently claimed by the Auger collaboration, this unbiased sky sample by H.E.S.S. is of interest since it includes (besides the targeted sources) 63 AGN within 100 Mpc, for which very-high energy gamma-ray flux limits are derived.Comment: 4 pages, 5 figures, Submitted to Proceedings of "4th International Symposium on High Energy Gamma-Ray Astronomy 2008

Observation of Galactic Gamma-ray Sources with VERITAS

We report on VERITAS observations at energies above 200 GeV of known or potential galactic gamma-ray sources. The observed objects comprise pulsars, pulsar wind nebulae, high-mass X-ray binaries and gamma-ray sources with unknown counterparts in other wavelengths. Among the highlights are the observation of variable gamma-ray emission from the X-ray binary LS I +61 303 and the detection of MGRO J1906+06/HESS J1906+063, an extended gamma-ray source which could not be associated with any obvious counterpart at lower energies.Comment: Fixed typos in source name

Scientific Highlights from Observations of Active Galactic Nuclei with the MAGIC Telescope

Since 2004, the MAGIC gamma-ray telescope has newly discovered 6 TeV blazars. The total set of 13 MAGIC-detected active galactic nuclei includes well-studied objects at other wavelengths like Markarian 501 and the giant radio galaxy M87, but also the distant the flat-spectrum radio quasar 3C 279, and the newly discovered TeV gamma-ray emitter S5 0716+71. In addition, also long-term and multi-wavelength studies on well-known TeV blazars and systematic searches for new TeV blazars have been carried out. Here we report selected highlights from recent MAGIC observations of extragalactic TeV gamma-ray sources, emphasizing the new physics insights MAGIC was able to contribute.Comment: 4 pages, 2 figures, submitted to proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008

Results of MAGIC on Galactic sources

MAGIC is a single-dish Cherenkov telescope located on La Palma (Spain), hence with an optimal view on the Northern sky. Sensitive in the 30 GeV-30 TeV energy band, it is nowadays the only ground-based instrument being able to measure high-energy gamma-rays below 100 GeV. We review the most recent experimental results on Galactic sources obtained using MAGIC. These include pulsars, binary systems, supernova remnants and unidentified sources.Comment: 4 pages, 8 figures, to appear in the proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008

Results of MAGIC on Galactic sources

MAGIC is a single-dish Cherenkov telescope located on La Palma (Spain), hence with an optimal view on the Northern sky. Sensitive in the 30 GeV-30 TeV energy band, it is nowadays the only ground-based instrument being able to measure high-energy gamma-rays below 100 GeV. We review the most recent experimental results on Galactic sources obtained using MAGIC. These include pulsars, binary systems, supernova remnants and unidentified sources.Comment: 4 pages, 8 figures, to appear in the proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008

Sub-mm/mm studies of the molecular gas in the Galactic disk; the TeV gamma ray SNR RXJ1713.7-3946 and the W28 high mass star forming region

Interstellar molecular clouds are gamma ray sources through the interactions with cosmic ray protons followed by production of neutral pions which decay into gamma rays. We present new NANTEN2 observations of the TeV gamma ray SNR RXJ1713.7-3946 and the W28 region in the 12CO J=2-1, 4-3 and 7-6 emission lines. In RXJ1713.7-3946 we confirm that the local molecular gas having velocities around -10 km/s shows remarkably good spatial correlations with the SNR. We show that the X ray peaks are well correlated with the molecular gas over the whole SNR and suggest that the interactions between the SNR and the molecular gas play an important role in cosmic ray acceleration via several ways including magnetic field compression. The CO J=4-3 distribution towards peak C shows a compact and dense cloud core having a size of about 1 pc as well as a broad wing. The core shows a notable anti-correlation with the Suzaku X ray image and is also associated with hard gamma rays as observed with HESS. Based on these findings, we present a picture that peak C is a molecular clump survived against the impact of the SN blast waves and is surrounded by high energy electrons emitting the X ray. The TeV gamma ray distribution is, on the other hand, more extended into the molecular gas, supporting the hadronic origin of gamma ray production. W28 is one of the most outstanding star forming regions exhibiting TeV gamma rays as identified through a comparison between the NANTEN CO dataset and HESS gamma ray sources. In the W28 region, we show the CO J=2-1 distribution over the whole region as well as the detailed image of the two TeV gamma ray peaks. One of them show strong CO J=7-6 emission, suggesting high excitation conditions in this high mass star forming core. A pursuit for the detailed mechanism to produce gamma rays is in progress.Comment: 9 pages, 8 Encapsulated Postscript figures, uses aipxfm.sty aipproc.cls aip-6s.clo aip-8d.clo aip-8s.cl

Time Averaged VHE Spectrum of Mrk 421 in 2005

The blazar Mrk421 was observed independently, but contemporaneously, in 2005 at TeV energies by MAGIC, the Whipple 10m telescope, and by a single VERITAS telescope during the construction phase of operations. A comparison of the time averaged spectra, in what was a relatively quiescent state, demonstrates the level of agreement between instruments. In addition, the increased sensitivity of the new generation instruments, and ever decreasing energy thresholds, questions how best to compare new observational data with archival results.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008

VERITAS Observations of the Coma Cluster of Galaxies

Clusters of galaxies are one of the few prominent classes of objects predicted to emit gamma rays not yet detected by satellites like EGRET or ground-based Imaging Atmospheric Cherenkov Telescopes (IACTs). The detection of Very High Energy (VHE, E > 100 GeV) gamma rays from galaxy clusters would provide insight into the morphology of non-thermal particles and fields in clusters. VERITAS, an array of four 12-meter diameter IACTs, is ideally situated to observe the massive Coma cluster, one of the best cluster candidates in the Northern Hemisphere. This contribution details the results of VERITAS observations of the Coma cluster of galaxies during the 2007-2008 observing season.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008

Multi-wavelength Observations of LS I +61 303 with VERITAS, Swift and RXT E: 2006-2008

A long term, multi-wavelength monitoring campaign on the TeV binary LS I +61 303 has been performed utilizing >300 GeV observations with VERITAS along with monitoring in the 0.2-10 keV band by RXTE and Swift between September 2006 and February 2008. The source was detected by VERITAS as a variable TeV source with flux values ranging from 5-20% of the Crab Nebula flux with the strongest flux levels appearing around apastron. X-ray observations by RXTE and Swift show the source as a highly variable hard X-ray source with flux values varying in the range of 0.5-3*10^-11 ergs cm^-2 s^-1 over a single orbital cycle. The 2007-2008 RXTE data set also shows the presence of several extremely large flaring episodes presenting a flux of up to 7.2*10^-11 ergs cm^-2 s^-1, the largest such flare recorded from this source. Comparison of the contemporaneous TeV and X-ray data does not show a correlation at this time, however, the sparsity of data sets do not preclude the existence of such a correlation.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008

VERITAS Observations of Extragalactic Non-Blazars

During the 2007/2008 season, VERITAS was used for observations at E>200 GeV of several extragalactic non-blazar objects such as galaxy clusters, starburst and interacting galaxies, dwarf galaxies, and nearby galaxies. In these proceedings, we present preliminary results from our observations of dwarf galaxies and M87. Results from observation of other non-blazar sources are presented in separate papers in the proceedings.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008