F.G. Schröder

An unidentified TeV source in the vicinity of Cygnus OB2

Deep observation (113 hrs) of the Cygnus region at TeV energies using the HEGRA stereoscopic system of air ˇ Cerenkov telescopes has serendipitously revealed a signal positionally inside the core of the OB association Cygnus OB2, at the edge of the 95% error circle of the EGRET source 3EG J2033+4118, and0:5 north of Cyg X-3. The source centre of gravity is RAJ2000 :2 0 hr 32 m 07 s 9:2 s 2:2 s ,D ecJ2000:+4130 0 30 00 2:0 0 0:4 0. The source is steady, has a post-trial significance of+4.6, indication for extension with radius 5:6 0 at the3 level, and has a dierential power-law flux with hard photon index of 1:9 0:3stat 0:3sys. The integral flux above 1 TeV amounts3% that of the Crab. No counterpart for the TeV source at other wavelengths is presently identified, and its extension would disfavour an exclusive pulsar or AGN origin. If associated with Cygnus OB2, this dense concentration of young, massive stars provides an environment conducive to multi-TeV particle acceleration and likely subsequent interaction with a nearby gas cloud. Alternatively, one could envisage-ray production via a jet-driven termination shock.

TeV gamma rays from the blazar H 1426+428 and the diffuse extragalactic background radiation

The detection of TeV -rays from the blazar H 1426+428 at an integral flux level of (4 2stat 1syst) 10 12 erg cm 2 s 1 above 1 TeV with the HEGRA imaging atmospheric Cherenkov telescope system is reported. H 1426+428 is located at a redshift of z = 0.129, which makes it the most distant source detected in TeV -rays so far. The TeV radiation is expected to be strongly absorbed by the diuse extragalactic background radiation (DEBRA). The observed energy spectrum of TeV photons is in good agreement with an intrinsic power law spectrum of the source/ E 1:9 corrected for DEBRA absorption. Statistical errors as well as uncertainties about the intrinsic source spectrum, however, do not permit strong statements about the density of the DEBRA infrared photon eld.

Ankle-like feature in the energy spectrum of light elements of cosmic rays observed with KASCADE-Grande

Recent results of the KASCADE-Grande experiment provided evidence for a mild knee-like structure in the all-particle spectrum of cosmic rays at

The TeV Energy Spectrum of Markarian 501 Measured with the Stereoscopic Telescope System of HEGRA during 1998 and 1999

E = 10^{16.92 \pm 0.10} \, \mathrm{eV}

Reanalysis of the high energy cutoff of the 1997 Mkn 501 TeV energy spectrum

, which was found to be due to a steepening in the flux of heavy primary particles. The spectrum of the combined components of light and intermediate masses was found to be compatible with a single power law in the energy range from

New method for the time calibration of an interferometric radio antenna array

10^{16.3} \, \mathrm{eV}

Measurement of cosmic-ray air showers with the Tunka Radio Extension (Tunka-Rex)

to

Radio measurements of the energy and the depth of the shower maximum of cosmic-ray air showers by Tunka-Rex

10^{18} \, \mathrm{eV}

Radio detection of Cosmic-Ray Air Showers and High-Energy Neutrinos

. In this paper, we present an update of this analysis by using data with increased statistics, originating both from a larger data set including more recent measurements and by using a larger fiducial area. In addition, optimized selection criteria for enhancing light primaries are applied. We find a spectral feature for light elements, namely a hardening at

Calibrating the absolute amplitude scale for air showers measured at LOFAR

E = 10^{17.08 \pm 0.08} \, \mathrm{eV}