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User interactions over social networks has been an emergent theme over the last several years. In contrast to previous work we focus on characterizing user communications patterns around an initial post, or conversation root. Specifically, we focus on how other users respond to these roots and how the complete conversation initiated by this root evolves(More)
VERITAS, the Very Energetic Radiation Imaging Telescope Array System, is an array of four 12 m diameter imaging atmospheric Cherenkov telescopes for gamma-ray astronomy above 100 GeV currently in operation in Arizona. The VERITAS Collaboration has developed VEGAS, the VERITAS Gamma-ray Analysis Suite, a data-analysis software package for the processing of(More)
While data are growing at a speed never seen before, parallel computing is becoming more and more essential to process this massive volume of data in a timely manner. Therefore, recently, concurrent computations have been receiving increasing attention due to the widespread adoption of multi-core processors and the emerging advancements of cloud computing(More)
The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10(12) electron volts and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we(More)
We report the detection of very high-energy γ-ray emission from the intermediate-frequency-peaked BL Lacertae object W Comae (z = 0.102) by VERITAS, an array of four imaging atmospheric-Cherenkov telescopes. The source was observed between January and April 2008. A strong outburst of γ-ray emission was measured in the middle of March, lasting for only four(More)
VERITAS employs a 12m segmented mirror and pixellated photomultiplier tube camera to detect the brief pulse of Cherenkov radiation produced by the extensive air shower initiated by a cosmic high-energy gamma ray. The VERITAS data acquisition system consists of a 500 Mega-Sample-Per-Second custom-built flash ADC system, which samples the Cherenkov light(More)
We report results from an intensive multi-wavelength monitoring campaign on the TeV blazar Mrk 421 over the period of 2003–2004. The source was observed simultaneously at TeV energies with the Whipple 10 m telescope and at X-ray energies with Rossi X-ray Timing Explorer (RXTE) during each clear night within the Whipple observing windows. Supporting(More)
Parallel and distributed computing is becoming essential to process in real time the increasingly massive volume of data collected by telecommunications companies. Existing computational paradigms such as MapReduce (and its popular open-source implementation Hadoop) provide a scalable, fault tolerant mechanism for large scale batch computations. However,(More)
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(More)
We present the discovery of very high energy (VHE) gamma-ray emission from the high-frequency-peaked BL Lac object 1ES 0806+524 (z=0.138) and the intermediate-frequency-peaked BL Lac object W Comae (z=0.102) with VERITAS. VHE emission was discovered from these objects during the 2007/2008 observing campaign, with a strong outburst from W Comae detected in(More)
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