Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session X8: Gamma Ray Astronomy |
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Sponsoring Units: DAP Chair: Steve Ritz, NASA/GSFC Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), Promenade A |
Tuesday, April 15, 2008 1:30PM - 1:42PM |
X8.00001: Observation of the high-frequency peaked BL Lac object 1ES 1218+304 with VERITAS Reshmi Mukherjee We report on observations of the high-frequency-peaked BL Lac object 1ES 1218+304 with the VERITAS array of several several imaging Cherenkov telescopes located at the Fred Laurence Whipple Observatory in Southern Arizona. A gamma-ray signal was detected with high significance for the observations taken during several months in the 2006-2007 observing season. Here we present results on the time variability and spectral properties of 1ES 1218+304, and discuss implications of the data. [Preview Abstract] |
Tuesday, April 15, 2008 1:42PM - 1:54PM |
X8.00002: Observation of very high-energy gamma-ray emission from Cassiopeia A with VERITAS Alexander Konopelko We report on observations of the supernova remnant Cassiopeia A carried out with the VERITAS array of four imaging atmospheric Cherenkov telescope for about 20 hrs between September and November 2007. The standard stereoscopic analysis developed by the VERITAS collaboration reveals the excess in the direction of Cassiopeia A at the significance level of 8s. The estimated integral flux is about 3\% of the Crab-Nebula flux above 1 TeV. The data are consistent with a point-like source. These observations enable measurement of a high quality spectrum of very high-energy gamma rays. The analysis results and theoretical implications will be presented at the symposium. [Preview Abstract] |
Tuesday, April 15, 2008 1:54PM - 2:06PM |
X8.00003: Observation of very high-energy gamma-ray emission from IC443 with VERITAS Viatcheslav Bugaev In 2007 the Very Energetic Radiation Imaging Telescope Array System (VERITAS) gamma-ray telescopes have been used to observe IC443, a shell-type SNR in its ISM-dominated stage of evolution that shows strong evidence of shock propagating into dense ($10^5 $cm$^{-3}$) OH clouds. We report on observations of IC443 carried out in spring 2007 (18 hours) and autumn 2007 (26 hours) with 3 and 4 VERITAS telescopes, correspondingly. The stereoscopic analysis developed by the VERITAS collaboration reveals the excess in the direction of IC443 at high significance level exceeding 6 sigma. These observations enable measurement of a spectrum of very high-energy gamma-rays. The analysis results and implications of the data on the origin of the high-energy emission will be presented. [Preview Abstract] |
Tuesday, April 15, 2008 2:06PM - 2:18PM |
X8.00004: Multiwavelength Observations of the Blazar 1ES 2344+514 Matthias Beilicke In 2007 and 2008, the Rossi X-ray Timing Explorer (RXTE) X-ray telescope and the Very Energetic Radiation Imaging Telescope Array System (VERITAS) gamma-ray telescope have been used to observe the blazar 1ES 2344+514. The observations captured several strong X-ray and TeV gamma-ray flares. In this contribution, we discuss the X-ray and TeV gamma-ray light curves and energy spectra. We discuss a detailed study of the correlations between the X-ray fluxes, X-ray spectral indices, TeV gamma-ray fluxes, and TeV gamma-ray spectral indices. Furthermore, we discuss implications of the data on the origin of the high-energy emission and the environment of the supermassive black hole that powers the blazar. [Preview Abstract] |
Tuesday, April 15, 2008 2:18PM - 2:30PM |
X8.00005: Blazar Monitoring with the Whipple 10m Telescope Kuen Lee In September 2005, the observing program was redefined and the 10m was dedicated almost exclusively to AGN monitoring. Since then the five Northern Hemisphere blazars that had already been detected at Whipple, Markarian 421, H1426+428, Markarian 501, 1ES1959+650 and 1ES2344+514, have been monitored routinely each night that they are visible. Thanks to the efforts of a large number of collaborators, a significant amount of data over the entire spectrum has been gathered on these five AGN. We report here on the overview and current status of this blazars multiwavelength, monitoring campaign which is ongoing. We present lightcurves and the broadband spectral energy distributions along with an interpretation in the framework of inverse-Compton models. [Preview Abstract] |
Tuesday, April 15, 2008 2:30PM - 2:42PM |
X8.00006: A Measurement of the Spatial Distribution of TeV Gamma Ray Emission from the Galactic Plane with Milagro Petra Huentemeyer Diffuse $\gamma$-ray emission produced by the interaction of cosmic ray particles with matter and radiation in the Galaxy can be used to probe the origin of cosmic rays. With its large field of view and long observation time, the Milagro Gamma Ray Observatory is an ideal instrument for surveying large regions of the Northern Hemisphere sky and for detecting diffuse $\gamma$-ray emission at high energies. The Milagro experiment has previously observed eight sources or source candidates in a Galactic plane survey. We determine the spatial distribution of the 15~TeV diffuse gamma ray emission by subtracting the flux contribution of these Milagro sources from the total $\gamma$-ray flux measured in the Galactic plane. The resulting fluxes and emission profiles are compared to the predictions of the GALPROP model. [Preview Abstract] |
Tuesday, April 15, 2008 2:42PM - 2:54PM |
X8.00007: A Survey of EGRET Sources at Very High Energies Chuan Chen The Milagro gamma-ray observatory employs a water-Cherenkov technique to continuously monitor the northern sky for TeV gamma-ray emission from astrophysical sources. Milagro has a high duty-cycle ($\sim$ 90\%) and wide aperture ($\sim$ 2sr). Seven and half years of Milagro data are used to search for gamma-ray emission from 129 EGRET sources in the Milagro field of view in the northern sky. Constraints on the fluxes at 5 TeV and 20 TeV will be presented. Different background rejection variables are used for different energy ranges. We compare Milagro fluxes with the fluxes measured by EGRET and Whipple and their extrapolation to Milagro energies. [Preview Abstract] |
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