Contribution to the 30th International Cosmic Ray Conference, Merida, Mexico, July 2007

abs/0709.3654

  VERITAS is an atmospheric Cherenkov telescope array designed to study astrophysi cal sources of very-high-energy gamma radiation. Located in southern Arizona, USA, the array consists of four 12m-diameter imaging Cherenkov telescopes. All four telescopes have been deployed at the basecamp of the Whipple Observatory and began full operation in early 2007. This paper describes the operational status of VERITAS, outlines the initial performance parameters of the instrument, and presents the latest results that have been obtained.

Contribution to the 30th International Cosmic Ray Conference, Merida, Mexico, July 2007

abs/0709.4299v1

  Between September 2006 and February 2007, the galactic binary LS I +61 303 was monitored in the TeV band with the VERITAS array of imaging Cherenkov telescopes. These observations confirm LS I +61 303 as a variable TeV gamma-ray source, with emission peaking between orbital phase 0.6 and 0.7. During this observational period, monitoring in the X-ray regime was also carried out using both the RXTE and Swift detectors, which offered complementary coverage of the source. Outbursts in the 0.2-10 keV band were observed by both satellites at close to the same orbital phase as the TeV peak during the 2 orbital cycles covered simultaneously in both bands. While this source has been extensively studied in the X-ray band in the past, this is the first observational campaign to utilize contemporaneous X-ray and TeV data on LS I +61 303.

Contribution to the 30th International Cosmic Ray Conference, Merida, Mexico, July 2007

abs/0709.3869

  In September 2005, the observing program of the Whipple 10 m gamma-ray telescope was redefined to be dedicated almost exclusively to AGN monitoring. Since then the five Northern Hemisphere blazars that had already been detected at Whipple are monitored routinely each night that they are visible. Thanks to the efforts of a large number of multiwavelength collaborators, the first year of this program has been very successful. We report here on the analysis of Markarian 421 observations taken from November, 2005 to May, 2006 in the gamma-ray, X-ray, optical and radio bands.

Contribution to the 30th International Cosmic Ray Conference, Merida, Mexico, July 2007

abs/0709.3695

  Observations of the blazars 1ES 0647+250 and 1ES 0806+524 with VERITAS are reported here. These objects are among the favoured candidate extragalactic sources in the very high-energy regime due to the presence of high-energy electrons and adequate seed photons. The presence of high-energy electrons is established from the location of the synrchrotron peak in the spectral energy distribution of the blazars. The presence of adequate seed photons is determined by the flux in the radio-through-optical wavebands. These are the key ingredients for very high-energy gamma-ray emission in the context of the synchrotron self-Compton model. The redshift of 1ES 0647+250 has been tentatively reported as 0.203 and the redshift of 1ES 0806+524 is 0.138, thus the detection of very high-energy gamma-ray emission from these objects could make significant contributions to the understanding of the extragalactic infrared background light. The analysis of these data relies on standard techniques in very high-energy gamma-ray astronomy, and the results are compared to previously reported upper limits and to theoretical predictions.