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Show 164 "VERITAS Observatio ns of the Extra galacti c Blazar BL La c" Spencer Hatch, (David Kieda) Department of Physics and Astronomy University of Utah research posters on the hill spring 2012 VERITAS Observations of Extragalactic Blazar BL Lac Spencer Hatch and Dr. David Kieda Department of Physics and Astronomy Student Photo Faculty Photo Image upper middle 2 Image lower left 4 Image upper right 3 Image lower middle 5 Behavior of BL Lac over the course of thirty-eight days in 2011 as seen by the VERITAS array. Observations were made in late May, early June, and the end of June into July. Note the flare occurring on June 28th on the right-hand side of the plot. The flare reached roughly four times the average light flux. Image of BL Lac produced by 27 twenty-minute VERITAS runs. The most significant contribution to the above image is the flaring episode on June 28th. The left-hand side of the illustration shows the spread of an air shower induced by a gamma ray. The right-hand side shows the three elliptical images generated on the telescopes due to the air shower, as well as the intersection of the three major axes of the images indicating the direction of the incoming gamma ray. Top: The VERITAS array, comprised of four Imaging Atmospheric Cherenkov Telescopes. It is located at the Fred Lawrence Whipple Observatory in Southern Arizona. Bottom: Close-up of the southernmost telescope at VERITAS. Large Photo: A simulated view of BL Lac, showing the accretion disk around BL Lac's supermassive black hole, as well as its jet and an emission traveling through the jet. Inlaid: An optical view of BL Lac. SUMMARY Using nine hours of data acquired from late May through early June, BL Lac was detected at a significance of level of 4.0 sigma On June 28th, 2011, BL Lac reached a gamma-ray flux of nearly four times its quiescent state The flare's estimated decay time gives a lower limit of ~12 light-minutes to the emission region of BL Lac BL Lac has not been observed in a flaring state despite an additional nine hours of observing time since June 28th, 2011 Spencer Hatch1 Credit: Rene Ong Credit: Konkoly Observatory 1 Weber State University David Kieda The active galaxy BL Lacertae (BL Lac), at a distance of roughly 900 million light years, is thought to harbor a supermassive black hole (~10^8 solar masses) at its center. This galaxy shows rapid optical flaring, which may be associ ated with the infall of material into the black hole. In late May 2011, the Fermi Large Area Telescope reported a large flare of very high energy gamma-rays from BL Lac, which led to a brief multi-telescope observational campaign involving several institutions, including the Very Energetic Radiation Imaging Telescope Array System (VERITAS) in southern Arizona. VERITAS observed BL Lac for a total of nine hours over the course of several weeks, from late May to early July. Standard analysis of VERITAS data from this period has shown little evidence for gamma-ray emission from BL Lac, with the very notable exception of a gamma-ray outburst on the evening of June 28th. I present a synopsis of the growing field of gamma-ray astronomy, as well as address potential constraints on the size of the emitting region of BL Lac based on the light fall-time during the June 28th flaring episode. |