56147520
Investigating Broadband Variability of the TeV Blazar 1ES 1959+ 650
We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band observations by the robotic telescopes Super-LOTIS and iTelescope, UV observations by Swift Ultraviolet and Optical Telescope, X-ray observations by the Swift X-ray Telescope, high-energy gamma-ray observations with the Fermi Large Area Telescope, and very-high-energy (VHE) gamma-ray observations by VERITAS above 315 GeV, all taken between 2012 April 17 and 2012 June 1 (MJD 56034 and 56079). The contemporaneous variability of the broadband spectral energy distribution is explored in the context of a simple synchrotron self Compton (SSC) model. In the SSC emission scenario, we find that the parameters required to represent the high state are significantly different than those in the low state. Motivated by possible evidence of gas in the vicinity of the blazar, we also investigate a reflected emission model to describe the observed variability pattern. This model assumes that the non-thermal emission from the jet is reflected by a nearby cloud of gas, allowing the reflected emission to re-enter the blob and produce an elevated gamma-ray state with no simultaneous elevated synchrotron flux. The model applied here, although not required to explain the observed variability pattern, represents one possible scenario which can describe the observations. As applied to an elevated VHE state of 66% of the Crab Nebula flux, observed on a single night during the observation period, the reflected emission scenario does not support a purely leptonic non-thermal emission mechanism. The reflected emission model does, however, predict a reflected photon field with sufficient energy to enable elevated gamma-ray emission via pion production with protons of energies between 10 and 100 TeV.
121713887
The detection at high and very high energies of the blazar 1ES 1312-423
The deep observation campaign led on Centaurus A with the High Energy Stereoscopic System (H.E.S.S.) has revealed a significant very high energy (VHE, E ≥ 100 GeV) excess coincident with the blazar 1ES 1312-423, 2° away from the radio galaxy. The source is also detected at high energy (HE, 20 MeV-300 GeV) with the Fermi Large Area Telescope (Fermi-LAT) after 3.5 years of all-sky monitoring. The high and very high energy spectra, together with Swift-XRT and ATOM observations are used to draw the first broad band spectral energy distribution (SED) of 1ES 1312-423. The non-thermal emission of this faint HBL is reproduced with a synchrotron self-Compton (SSC) model combined with a black-body spectrum for the host galaxy.
119248446
MULTIWAVELENGTH OBSERVATIONS OF MARKARIAN 421 IN 2005-2006
Since 2005 September, the Whipple 10 m Gamma-ray Telescope has been operated primarily as a blazar monitor. The five northern hemisphere blazars that have already been detected at the Whipple Observatory, Markarian 421 (Mrk 421), H1426+428, Mrk 501, 1ES 1959+650, and 1ES 2344+514, are monitored routinely each night that they are visible. We report on the Mrk 421 observations taken from 2005 November to 2006 June in the gamma-ray, X-ray, optical, and radio bands. During this time, Mrk 421 was found to be variable at all wavelengths probed. Both the variability and the correlations among different energy regimes are studied in detail here. A tentative correlation, with large spread, was measured between the X-ray and gamma-ray bands, while no clear correlation was evident among the other energy bands. In addition to this, the well-sampled spectral energy distribution of Mrk 421 (1101+384) is presented for three different activity levels. The observations of the other blazar targets will be reported separately.
118220245
Cherenkov and Jansky: Our Understanding of AGN at the Highest Energies
Misaligned blazars have been the subject of some of the most successful radio and gamma-ray multiwavelength campaigns. These campaigns have included many of the major ground and space based gamma-ray telescopes and span decades of energy. Even though misaligned blazars account for only a small number of the total AGN detected at VHE, they provide a unique view on the AGN population. By viewing blazars at larger angles to our line of sight, they become a unique laboratory for the study of AGN jet substructure and the morphology of non-thermal emission processes. This contribution will discuss our understanding of three VHE misaligned blazars.
1747404
Thick pixelated CZT detectors with isolated steering grids
We explore the possibility to improve the performance of 0.5 cm thick cadmium zinc telluride (CZT) detectors with the help of steering grids on the anode side of the detectors. Steering grids can improve the energy resolution of CZT detectors by enhancing the small pixel effect; furthermore, they can increase their detection efficiency by steering electrons to the anode pixels which otherwise would drift to the area between pixels. Previously, the benefit of steering grids had been compromised by additional noise associated with currents between the steering grids and the anode pixels. We use thin film deposition techniques to isolate the steering grid from the CZT substrate by a 150 nm thick layer of the isolator Al2O3. While the thin layer does not affect the beneficial effect of the steering grid on the weighting potentials and the electric field inside the detector, it suppresses the currents between the steering grid and the anode pixels. In this contribution, we present first results from a 2times2times0.5 cm3 CZT detector with 8times8 pixels that we tested before and after deposition of an isolated steering grid. The steering grid improves the 662 keV energy resolution of the detector by a factor of 1.3 (from about 2% to about 1.5%), while not reducing the detection efficiency. To gain further insights into the detector response in the region between pixels, we measured energy spectra with a collimated 137Cs source. The collimator measurements can be used to enhance our understanding of energy spectra measured under flood illumination of the detectors
109887842
Control, Monitoring and Analysis Software for the VERITAS Array
VERITAS is an array of four 12 m diameter Atmospheric Cherenkov Telescopes located in southern Arizona operating since January 2007. In this contribution we discuss the various software systems needed to operate the array including the data acquisition, online analysis, real time hardware monitoring and offline analysis.
118390823
Rapidity gaps in hard processes at D0
Latest results on jet production with rapidity gaps at the Fermilab Tevatron Collider are presented. Jet production via color-singlet exchange at high momenta transfer is observed as a class of events with low particle multiplicity (or rapidity gaps) between the two highest transverse energy jets. The particle multiplicity in various regions, and the dependencies on jet pseudorapidity separation and jet transverse energy are studied for these events. Results from two classes of dijet events with one or two forward rapidity gaps are also presented. The topology of these events is consistent with expectations for hard single diffraction and hard double pomeron exchange processes, respectively.
92351247
Probing color singlet exchange in proton anti-proton collisions at 630-GeV and 1800-GeV