Astrophysics
We present a limit on the flux of relativistic monopoles obtained during 994 days of operation of the Baikal neutrino telescope NT200. The search for relativistic monopoles is based on the enormous amount of Cherenkov radiation emitted by…
We present the results of a search for high energy extraterrestrial neutrinos with the Baikal underwater Cherenkov detector NT200, based on data taken in 1998 - 2002 (1038 live days).Upper limits on the diffuse fluxes of…
The Baikal neutrino telescope NT200 takes data since 1998. In 2005, the deployment of three additional strings for common operation with NT200 was finished. We describe the physics program and the design of the new telescope named NT200+…
New results from the Baikal neutrino telescope NT200, based on the first 5 years of operation (1998-2003), are presented. We derive an all-flavor limit on the diffuse flux of astrophysical neutrinos between 20 TeV and 50 PeV, extract an…
The Pierre Auger Observatory is being used to study cosmic rays with energies larger than 10 EeV. An essential quantity that must be deduced from data is the lateral distribution function (LDF). Knowledge of the LDF is important for the…
We present the results of a search for cosmic ray point sources at energies above 10^19 eV in the HiRes stereo data set. The analysis is based on a maximum likelihood ratio test using the probability density function for each event rather…
The bright gamma-ray burst GRB050525a has been detected with the Swift observatory, providing unique multiwavelength coverage from the very earliest phases of the burst. The X-ray and optical/UV afterglow decay light curves both exhibit a…
We fit the HiRes ultra-high energy cosmic ray (UHECR) spectrum measurements with broken power laws in order to identify features. These fits find the previously observed feature known as the Ankle at 10**18.5 eV, as well as evidence for a…
While stereo measurements of extensive air showers allow a more precise determination of the depth of shower maximum and hence the composition of UHECR's, monocular measurements allow one to go much lower in energy. Since the composition of…
We present the results of searches for correlation between ultra--high-energy cosmic rays observed in stereo mode by the High Resolution Fly's Eye (HiRes) experiment and objects of the BL Lac subclass of active galaxies. In particular, we…
The first of the four atmospheric Cherenkov telescopes of the VERITAS array has been in operation at the Mt. Hopkins base camp since January 2005. The telescope has met all specifications. We present here a description of the technical…
The 499 pixel photomultiplier cameras of the VERITAS gamma ray telescopes are instrumented with 500MHz sampling Flash ADCs. This paper describes a preliminary investigation of the best methods by which to exploit this information so as to…
Cherenkov light from cosmic-ray muons is a significant source of background for the Imaging Atmospheric Cherenkov Technique. However, muon events are also valuable as a diagnostic tool because they produce distinctive ring images, and the…
Some candidate dark matter particles, such as neutralinos in supersymmetry, would annihilate producing GeV/TeV gamma rays. We report on recent observations of two dwarf spheroid galaxies, Draco, Ursa Minor, the compact elliptical galaxy…
Daily monitoring of Mrk 421 in the X-ray and TeV bands during the first half of 2004 showed rapid flaring events above an elevated base flux level, culminating from March to May 2004 at an average flux level matching the highest detected…
The Whipple 10 meter atmospheric Cherenkov telescope has made observations of the region known as the Cygnus arm. This region has been recently reported by the Milagro experiment to contain a diffuse TeV gamma-ray source centered at RA=308…
The Very High Energy Radiation Telescope Array (VERITAS) is a system of four imaging Cherenkov telescopes currently under construction at Kitt Peak, Arizona, USA. The first telescope has been in operation at the Mt. Hopkins basecamp since…
The first VERITAS (Very Energetic Radiation Imaging Telescope Array System) telescope has been in operation at the basecamp of the Whipple Observatory since January 2005. Here we present initial observations of AGN made using this…
We report on observations of the Perseus cluster of galaxies using the 10 m Whipple $\gamma$-ray telescope during the 2004-2005 observing season. We apply a two dimensional analysis technique to allow us to scrutinize the cluster for TeV…
We present studies of systematic uncertainties in the measurement of the ultra-high energy cosmic ray (UHECR) spectrum with the FADC detector of the High Resolution Fly's Eye experiment (HiRes-II). One source of uncertainties lies in the…