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8 results on '"C. Dowdall"'

1. The Whipple Observatory 10m gamma-ray telescope, 1997–2006

Author

G. E. Kenny, O. Celik, M. J. Lang, P. Moriarty, D. Petry, G. H. Gillanders, A. Konopelko, J. P. Finley, John Kildea, D. A. Carter-Lewis, F. Krennrich, T. C. Weekes, A. Syson, J. Millis, Y. C. K. Chow, J. Lloyd-Evans, I. D. Perez, I. Jung, M. K. Daniel, C. Duke, D. J. Fegan, H. J. Rose, R. J. White, S. P. Wakely, Daniel Gall, S. B. Hughes, J. S. Perkins, M. Jordan, A. W. Smith, J. Grube, Jamie Holder, J. H. Buckley, M. Schroedter, C. Dowdall, K. Gutierrez, John Toner, P. Cogan, S. M. Bradbury, G. H. Sembroski, R. W. Atkins, J. Knapp, P. A. Ogden, I. H. Bond, Henric Krawczynski, Lucy Fortson, R. A. Ong, D. Horan, S. LeBohec, J. Hall, T. Nagai, P. Rebillot, Martin Pohl, K. Kosack, Mark N. Quinn, Wei Cui, L. Valcarcel, M. Kertzman, G. Blaylock, H. M. Badran, V. V. Vassiliev, Tony Hall, Abraham D. Falcone, F. Pizlo, S. J. Fegan, and John L. Quinn

Subjects
Physics, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astronomy and Astrophysics, Context (language use), Gamma-ray astronomy, Cherenkov Telescope Array, law.invention, Primary mirror, Telescope, Observatory, law, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Cherenkov radiation, Fermi Gamma-ray Space Telescope
Abstract

Details are presented of the Whipple Observatory’s 10 m atmospheric Cherenkov telescope and camera, as it evolved during the period 1997 until 2006. The design of the telescope and camera’s optical and electronic systems is discussed together with a detailed description of the four-stage GRANITE (Gamma-RAy New Imaging TElescope) upgrade program, undertaken during the same time period. The objective of the upgrade was to improve the telescope’s sensitivity for the detection of very-high-energy gamma-rays. Results from the program are provided and are briefly discussed in the context of the design of VERITAS.

Published
2007
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2. Status report from VERITAS

Author

Jamie Holder, I. Jung, M. J. Lang, Gernot Maier, S. P. Wakely, R. G. Wagner, D. A. Carter-Lewis, D. Steele, J. S. Perkins, P. Cogan, M. K. Daniel, Henric Krawczynski, David Kieda, E. Hays, John Kildea, Tulun Ergin, G. H. Gillanders, P. Kaaret, K G Gutierrez, A. J.R. Weinstein, Wei Cui, P Fortin, D. Horan, L. Valcarcel, G. E. Kenny, Thomas Brian Humensky, S. P. Swordy, C. Dowdall, David A. Williams, A. D. Falcone, S. J. Fegan, Karen Byrum, Stephanie Wissel, M. Schroedter, Lucy Fortson, S. M. Bradbury, V. V. Vassiliev, F. Pizlo, A. Konopelko, D. S. Hanna, A. Imran, John L. Quinn, G. H. Sembroski, K. G. Gibbs, H. J. Rose, J. H. Buckley, F. Krennrich, S. B. Hughes, Omer Celik, J. A. Toner, G. Blaylock, T. C. Weekes, T. Nagai, P. Moriarty, R. J. White, J. Grube, A. W. Smith, C. Duke, R. A. Ong, S. LeBohec, and J. Millis

Subjects
Physics, History, Observatory, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, High Energy Physics::Experiment, Astrophysics, Status report, Computer Science Applications, Education
Abstract

VERITAS is a ground-based gamma-ray observatory covering energies between 100 GeV and 50 TeV and will start operating by January 2007. We give a brief report of the construction status and performance characteristics of the telescopes.

Published
2007
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3. Very High Energy Observations of Gamma‐Ray Burst Locations with the Whipple Telescope

Author

M. Schroedter, P. Cogan, J. Grube, R. W. Atkins, Vladimir Vassiliev, Y. C. K. Chow, M. K. Daniel, Karen Byrum, Gernot Maier, P. Fortin, A. D. Falcone, David Kieda, S. P. Wakely, John Kildea, H. Krawczynski, I. de la Calle Perez, Stephan LeBohec, S. P. Swordy, Jeremy Perkins, H. J. Rose, R. A. Ong, J. H. Buckley, R. J. White, K. Ragan, S. J. Fegan, D. Steele, P. T. Reynolds, M. Kertzman, M. J. Lang, Lucy Fortson, S. B. Hughes, R. G. Wagner, G. H. Sembroski, Thomas Brian Humensky, J. Hall, Jamie Holder, S. M. Bradbury, D. J. Fegan, P. Moriarty, John L. Quinn, G. Blaylock, J. P. Finley, T. C. Weekes, K. J. Gutierrez, D. Horan, T. N. Nagai, D. Petry, G. H. Gillanders, Frank Krennrich, C. Dowdall, O. Celik, D. S. Hanna, D. A. Williams, G. E. Kenny, H. M. Badran, John Toner, Wei Cui, L. Valcarcel, and Mark N. Quinn

Subjects
Physics, gamma rays : bursts, gamma rays : observations, Astronomy & Astrophysics, High energy, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Afterglow, law.invention, Telescope, compton emission, refreshed shocks, external matter, light-curve, afterglows, tev, models, flares, discovery, search, Space and Planetary Science, Observatory, law, Spectral energy distribution, Blazar, Gamma-ray burst, Flare
Abstract

Gamma-ray burst (GRB) observations at very high energies (VHE, E > 100 GeV) can impose tight constraints on some GRB emission models. Many GRB afterglow models predict a VHE component similar to that seen in blazars and plerions, in which the GRB spectral energy distribution has a double-peaked shape extending into the VHE regime. VHE emission coincident with delayed X-ray flare emission has also been predicted. GRB follow-up observations have had high priority in the observing program at the Whipple 10m Gamma-ray Telescope and GRBs will continue to be high priority targets as the next generation observatory, VERITAS, comes on-line. Upper limits on the VHE emission, at late times (>~4 hours), from seven GRBs observed with the Whipple Telescope are reported here., Accepted for publication in the January 20, 2007 volume of the Astrophysical Journal, 655, 396

Published
2007
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4. The first veritas telescope

Author

Geza Gyuk, A. Milovanovic, Philip Kaaret, F. Krennrich, A. Syson, M. K. Daniel, Gernot Maier, D. A. Carter-Lewis, G. E. Kenny, J. P. Finley, K. Ragan, D. Horan, T. C. Weekes, S. P. Wakely, Y. C. K. Chow, Abraham D. Falcone, C. Duke, R. A. Ong, John Toner, F. Pizlo, R. G. Wagner, H. Manseri, E. Roache, J. Grube, S. LeBohec, S. P. Swordy, P. A. Ogden, Reshmi Mukherjee, Jamie Holder, M. J. Lang, I. Jung, K. J. Gutierrez, R. J. White, John L. Quinn, S. B. Hughes, Henric Krawczynski, P. Moriarty, K. G. Gibbs, S. M. Bradbury, Karen Byrum, G. Sleege, John Kildea, E.K. Little, M. Schroedter, G. Blaylock, J. Hall, J. S. Perkins, David A. Williams, C. Dowdall, P. Fortin, H. J. Rose, P. Cogan, Martin Pohl, R. W. Atkins, J. H. Buckley, P. T. Reynolds, D. Petry, E. Hays, V. V. Vassiliev, David Kieda, Lucy Fortson, Paul Dowkontt, Wei Cui, L. Valcarcel, H. M. Badran, O. J. Glidewell, D. S. Hanna, A. Imran, E. Linton, J. Knapp, I. de la Calle Perez, Thomas Brian Humensky, G. H. Sembroski, G. H. Gillanders, O. Celik, S. J. Fegan, and D. Steele

Subjects
tev gamma-rays, Astrophysics::High Energy Astrophysical Phenomena, Monte Carlo method, FOS: Physical sciences, X-ray telescope, Astrophysics, system, 01 natural sciences, law.invention, spectrum, Telescope, project, law, 0103 physical sciences, Calibration, Astrophysics::Solar and Stellar Astrophysics, crab-nebula, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Cherenkov radiation, gamma ray astronomy, cherenkov telescopes, atmospheric cherenkov telescope, imaging technique, Physics, 010308 nuclear & particles physics, Astrophysics (astro-ph), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astronomy and Astrophysics, Gamma-ray astronomy, Cherenkov Telescope Array, Crab Nebula, Astrophysics::Earth and Planetary Astrophysics
Abstract

The first atmospheric Cherenkov telescope of VERITAS (the Very Energetic Radiation Imaging Telescope Array System) has been in operation since February 2005. We present here a technical description of the instrument and a summary of its performance. The calibration methods are described, along with the results of Monte Carlo simulations of the telescope and comparisons between real and simulated data. The analysis of TeV $\gamma$-ray observations of the Crab Nebula, including the reconstructed energy spectrum, is shown to give results consistent with earlier measurements. The telescope is operating as expected and has met or exceeded all design specifications., Comment: Accepted by Astroparticle Physics

Published
2006

5. A new search for primordial black hole evaporations using the whipple gamma-ray telescope

Author

M. K. Daniel, E. Linton, Gernot Maier, S. P. Wakely, P. Fortin, J. H. Buckley, L. Valcarcel, J. Knapp, John Kildea, John L. Quinn, G. E. Kenny, P. J. Boyle, K. J. Guiterrez, M. J. Lang, K. Ragan, H. M. Badran, I. Jung, R. A. Ong, David Kieda, P. Rebillot, J. Hall, S. LeBohec, Jamie Holder, A. D. Falcone, S. P. Swordy, D. Horan, G. Blaylock, Karen Byrum, J. P. Finley, Martin Pohl, P. Cogan, F. Pizlo, R. W. Atkins, P. Moriarty, Y. C. Chow, G. H. Sembroski, T. C. Weekes, C. Dowdall, M. Kertzman, D. S. Hanna, D. J. Fegan, Thomas Brian Humensky, S. J. Fegan, D. Steele, Jeremy Perkins, Henric Krawczynski, R. J. White, S. B. Hughes, O. Celik, P. T. Reynolds, and D. A. Carter-Lewis

Subjects
Physics, bursts, media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, cosmic-rays, Astronomy, Astronomy and Astrophysics, Cosmic ray, Primordial black hole, Astrophysics, gamma ray bursts, black holes, Galaxy, Universe, matter, scale, General Relativity and Quantum Cosmology, Micro black hole, Orders of magnitude (time), Gamma-ray burst, Fermi Gamma-ray Space Telescope, media_common
Abstract

Stephen Hawking's prediction that black holes should radiate like black bodies has several important consequences, including the possibility of the detection of small (similar to 10(15) g) black holes created in the very early universe. The detection of such primordial black holes ( PBHs) would be an important discovery, not only confirming Hawking's theory, but also providing valuable insights into the history of the early universe. A search through 5.5 years of archival data from the Whipple Atmospheric Cerenkov Telescope is made for TeV gamma-ray bursts on 1, 3, and 5 s timescales. On the basis of a null result from this direct search for PBH evaporations, an upper limit of 1.08 x 10(6) pc(-3) yr(-1) (99% CL) is set on the PBH evaporation rate in the local region of the galaxy, assuming the Standard Model of particle physics. This is more than a factor of two better than the previous limit at this energy range and includes longer timescales than have previously been explored. Comparison of this result with previous limits on the fraction of the critical density comprised by PBHs, Omega(pbh), depends strongly on assumptions made about PBH clustering; in models predicting strong PBH clustering, the limit in this work could be as many as ten orders of magnitude more stringently than those set by diffuse MeV gamma-ray observations.

Published
2006

6. VERITAS: status c.2005

Author

S. M. Bradbury, D. A. Carter-Lewis, S. P. Swordy, K. J. Guitterez, V. V. Vassiliev, M. Schroedter, F. Pizlo, G. E. Kenny, P. A. Ogden, Paul Dowkontt, Reshmi Mukherjee, E. Linton, H. M. Badran, J. Hall, Y. C. Chow, Tony Hall, T. B. Humensky, B. Power-Mooney, P. Fortin, H. J. Rose, Tulun Ergin, I. de la Calle Perez, David R. Williams, Henric Krawczynski, T. N. Nagai, Wei Cui, A. Milovanovic, D. Kiedai, D. S. Hanna, J. S. Perkins, Dirk Petry, John L. Quinn, K. Kosack, K. G. Gibbs, J. Knapp, A. M. Hillas, John Kildea, R. G. Wagner, D. Horan, M. J. Lang, K. L. Bryum, Lucy Fortson, P. T. Reynolds, P. Kaaret, M. K. Daniel, A. D. Falcone, A. Syson, P. J. Boyle, L. Valcarcel, G. H. Gillanders, C. Dowdall, S. Gammell, E. Hays, P. Moriarty, Gernot Maier, J. Grube, J. Lloyd-Evans, D. Steele, R. A. Ong, G. H. Sembroski, H. Manseri, S. P. Wakely, G. Walker, S. LeBohec, C. Duke, J. P. Finley, J. A. Toner, T. C. Weekes, S. B. Hughes, M. Pohl, J. A. Zweerink, K. Ragan, P. Rebillot, M. A. Olevitch, Jamie Holder, Mark N. Quinn, D. J. Fegan, M. Kertzmann, I. H. Bond, S. J. Fegan, P. Cogan, R. W. Atkins, R. J. White, Omer Celik, G. Blaylock, J. H. Buckley, and F. Krennrich

Subjects
Computer science, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Radiation imaging, Astronomy, Cosmic ray, Gamma-ray astronomy, law.invention, Telescope, law, Astrophysics::Solar and Stellar Astrophysics, Astronomical telescopes, Gamma detection, Astrophysics::Galaxy Astrophysics, Cherenkov radiation, Gamma ray detection
Abstract

VERITAS (Very Energetic Radiation Imaging Telescope Array System), is one of a new generation of TeV gamma‐ray observatories. The current status of its construction is described here. The first two telescopes and cameras have been completed and meet the design specifications; the full array of four telescopes could be operational by the end of 2006.

Published
2006
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7. Whipple Telescope Observations of LS I +61 303: 2004-2006

Author

A. Smith, R. W. Atkins, S. Bradbury, O. Celik, Y. C. K. Chow, P. Cogan, C. Dowdall, S. J. Fegan, P. Fortin, D. Gall, G. H. Gillanders, J. Grube, K. J. Gutierrez, T. A. Hall, D. Hanna, J. Holder, D. Horan, S. B. Hughes, T. B. Humensky, I. Jung, P. Kaaret, G. Kenny, M. Kertzman, D. B. Kieda, A. Konopelko, H. Krawczynski, F. Krennrich, M. J. Lang, S. Le Bohec, G. Maier, J. Millis, P. Moriarty, R. A. Ong, J. S. Perkins, K. Ragan, G. H. Sembroski, J. A. Toner, L. Valcarcel, V. V. Vassiliev, R. G. Wagner, S. P. Wakely, T. C. Weekes, R. J. White, and D. A. Williams

Subjects
Physics, High energy, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, law.invention, Telescope, Space and Planetary Science, law, MAGIC (telescope)
Abstract

In this paper we present the results of the past two years' observations on the galactic microquasar LS I +61 303 with the Whipple 10m gamma-ray telescope. The recent MAGIC detection of the source between 200 GeV and 4 TeV suggests that the source is periodic with very high energy (VHE) gamma-ray emission linked to its orbital cycle. The entire 50-hour data set obtained with Whipple from 2004 to 2006 was analyzed with no reliable detection resulting. The upper limits obtained in the 2005-2006 season covered several of the same epochs as the MAGIC Telescope detections, albeit with lower sensitivity. Upper limits are placed on emission during the orbital phases of 0->0.1 and 0.8->1, phases which are not included in the MAGIC data set., 4 pages, 5 figures, To appear in Astrophysics and Space Science (Proceedings of "The multimessenger approach to unidentified gamma-ray sources")

Published
2006
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8. Search for High Energy Gamma Rays from an X-ray Selected Blazar Sample

Author

I. de la Calle Perez, I. H. Bond, P. J. Boyle, S. M. Bradbury, J. H. Buckley, D. A. Carter‐Lewis, O. Celik, W. Cui, C. Dowdall, C. Duke, A. Falcone, D. J. Fegan, S. J. Fegan, J. P. Finley, L. Fortson, J. A. Gaidos, K. Gibbs, S. Gammell, J. Hall, T. A. Hall, A. M. Hillas, J. Holder, D. Horan, M. Jordan, M. Kertzman, D. Kieda, J. Kildea, J. Knapp, K. Kosack, H. Krawczynski, F. Krennrich, S. LeBohec, E. T. Linton, J. Lloyd‐Evans, P. Moriarty, D. Muller, T. N. Nagai, R. A. Ong, M. Page, R. Pallassini, D. Petry, B. Power‐Mooney, J. Quinn, P. Rebillot, P. T. Reynolds, H. J. Rose, M. Schroedter, G. H. Sembroski, S. P. Swordy, V. V. Vassiliev, S. P. Wakely, G. Walker, and T. C. Weekes

Subjects
High energy, tev energies, Astrophysics::High Energy Astrophysical Phenomena, Flux, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, telescope, law.invention, Telescope, bl lacertae objects, law, emission, gamma rays : observations, flare, Blazar, bl lacertae objects : individual (rgb j0214+517, rgb j1117+202, rgb j1725+118, ies 0033+595, 1es 0120+340, Physics, Spectral properties, Astrophysics (astro-ph), X-ray, Gamma ray, Astronomy and Astrophysics, Sample (graphics), radiation, 1es 0229+200, 1es 0806+524, 1es 1426+428, 1es 1553+113, 1es 1959+650), Space and Planetary Science, markarian-501, active galactic nuclei, absorption, discovery
Abstract

Our understanding of blazars has been greatly increased in recent years by extensive multi-wavelength observations, particularly in the radio, X-ray and gamma-ray regions. Over the past decade the Whipple 10m telescope has contributed to this with the detection of 5 BL Lacertae objects at very high gamma-ray energies. The combination of multi-wavelength data has shown that blazars follow a well-defined sequence in terms of their broadband spectral properties. Together with providing constraints on emission models, this information has yielded a means by which potential sources of TeV emission may be identified and predictions made as to their possible gamma-ray flux. We have used the Whipple telescope to search for TeV gamma-ray emission from eight objects selected from a list of such candidates. No evidence has been found for VHE emission from the objects in our sample, and upper limits have been derived for the mean gamma-ray flux above 390GeV. These flux upper limits are compared with the model predictions and the implications of our results for future observations are discussed., 15 pages, 2 figures, Accepted for publication in ApJ

Published
2003

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