New LED transmitters have been used to develop a new method of fast analog transmission of PMT pulses over large distances. The transmitters, consisting basically of InGaAsP LEDs with the maximum ...emission of light at 1300 nm, allow the transmission of fast photomultiplier pulses over distances of more than 2 km. The shape of the photomultiplier pulses is maintained, with an attenuation less than 1 dB/km. Typical applications of analog optical signal transmission are surface air shower detectors and under water/ice neutrino experiments, which measure fast Cherenkov or scintillator pulses at large detector distances to the central DAQ system.
Results from the first two years of VERITAS observations Krennrich, F.; Bautista, M.; Beilicke, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2011, Letnik:
630, Številka:
1
Journal Article
Recenzirano
The VERITAS observatory is an imaging atmospheric Cherenkov telescope array located in southern Arizona and covers an energy range between 100
GeV and 30
TeV. The VERITAS collaboration pursues a ...rigorous observing program that targets a range of key science objectives in astrophysics and particle physics; the understanding of the origin of cosmic rays, the search for supersymmetric dark matter self-annihilation, illuminating the connection between black holes and relativistic jets and constraints to the cosmological diffuse infrared background. We provide a summary of results from the first two years of observations with the full 4-telecope array reported at RICAP09.
We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and ...VERITAS at a persistent level of ~6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching ~20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured spectra for absorption by the extragalactic background light, 1ES 1218+304 and a number of other blazars are found to have differential photon indices Delta *G<= 1.5. The difficulty in modeling these hard spectral energy distributions in blazar jets has led to a range of theoretical Delta *g-ray emission scenarios, one of which is strongly constrained by these new VERITAS observations. We consider the implications of the observed light curve of 1ES 1218+304, which shows day scale flux variations, for shock acceleration scenarios in relativistic jets, and in particular for the viability of kiloparsec-scale jet emission scenarios.
We present an analysis of the X-ray spectra of two strongly magnetic cataclysmic variables, DP Leo and WW Hor, made using XMM-Newton. Both systems were in intermediate levels of accretion. Hard ...optically thin X-ray emission from the shocked accreting gas was detected from both systems, while a soft blackbody X-ray component from the heated surface was detected only in DP Leo. We suggest that the lack of a soft X-ray component in WW Hor is owing to the fact that the accretion area is larger than in previous observations with a resulting lower temperature for the re-processed hard X-rays. Using a multi-temperature model of the post-shock flow, we estimate that the white dwarf in both systems has a mass greater than 1 M⊙. The implications of this result are discussed. We demonstrate that the ‘soft X-ray excess’ observed in many magnetic cataclysmic variables can be partially attributed to using an inappropriate model for the hard X-ray emission.
LS I +61 303 is one of only a few high-mass X-ray binaries currently detected at high significance in very high energy -rays. The system was observed over several orbital cycles (between 2006 ...September and 2007 February) with the VERITAS array of imaging air Cerenkov telescopes. A signal of -rays with energies above 300 GeV is found with a statistical significance of 8.4 standard deviations. The detected flux is measured to be strongly variable; the maximum flux is found during most orbital cycles at apastron. The energy spectrum for the period of maximum emission can be characterized by a power law with a photon index of image and a flux above 300 GeV corresponding to 15%-20% of the flux from the Crab Nebula.
The ground-based gamma-ray observatory VERITAS (Very Energetic Radiation Imaging Telescope Array System) is sensitive to photons of astrophysical origin with energies in the range between \(\approx ...85\) GeV to \(\approx 30\) TeV. The instrument consists of four 12-m diameter imaging Cherenkov telescopes operating at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona. VERITAS started four-telescope operations in 2007 and collects about 1100 hours of good-weather data per year. The VERITAS collaboration has published over 100 journal articles since 2008 reporting on gamma-ray observations of a large variety of objects: Galactic sources like supernova remnants, pulsar wind nebulae, and binary systems; extragalactic sources like star forming galaxies, dwarf-spheroidal galaxies, and highly-variable active galactic nuclei. This note presents VTSCat: the catalog of high-level data products from all VERITAS publications.
PDF
