The MAGIC extragalactic sky

The MAGIC telescope, with its 17-m diameter mirror, is currently the largest single-dish Imaging Air Cherenkov Telescope. It is located on the Canary Island of La Palma, at an altitude of 2200 m above sea level, and is operating since 2004. The accessible energy range is in the very high energy (VHE, E>100 GeV) gamma-ray domain, and roughly 40% of the duty cycle is devoted to observation of extragalactic sources. Due to the lowest energy threshold (25 GeV), it can observe the deepest universe, and it is thus well suited for extragalactic observations. The strategies of extragalactic observations by MAGIC are manifold: long time monitoring of known TeV blazars, detailed study of blazars during flare states, multiwavelength campaigns on most promising targets, and search for new VHE gamma-ray emitters. In this talk, highlights of observations of extragalactic objects will be reviewed.Comment: 8 pages, 5 figures, submitted to proceedings of "44th Rencontres do Moriond 2009, Very High Energy Phenomena in the Universe", February 1-8, 200

Measurement of the Tau Lepton Polarisation at LEP2

A first measurement of the average polarisation P_tau of tau leptons produced in e+e- annihilation at energies significantly above the Z resonance is presented. The polarisation is determined from the kinematic spectra of tau hadronic decays. The measured value P_tau = -0.164 +/- 0.125 is consistent with the Standard Model prediction for the mean LEP energy of 197 GeV.A first measurement of the average polarisation Pτ of tau leptons produced in e + e − annihilation at energies significantly above the Z resonance is presented. The polarisation is determined from the kinematic spectra of tau hadronic decays. The measured value Pτ=−0.164±0.125 is consistent with the Standard Model prediction for the mean LEP energy of 197 GeV.A first measurement of the average polarisation P_tau of tau leptons produced in e+e- annihilation at energies significantly above the Z resonance is presented. The polarisation is determined from the kinematic spectra of tau hadronic decays. The measured value P_tau = -0.164 +/- 0.125 is consistent with the Standard Model prediction for the mean LEP energy of 197 GeV

MAGIC and H.E.S.S. detect VHE gamma rays from the blazar OT081 for the first time: a deep multiwavelength study

https://pos.sissa.it/395/815/pdfPublished versio

The transparency of the Universe to Very High Energy Photons.

The detection of the blazar 3C279 at a record distance z=0.54 by MAGIC, and of other distant blazars by H.E.S.S. and VERITAS, indicate that the Universe is more transparent to very-high-energy gamma rays than previously thought on the basis of the estimates of the density of Extragalactic Background Light. The physical implications of these measurements will be discussed