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Astrophysics and Astronomy

Physical Sciences Publications

2013

Articles 1 - 7 of 7

Full-Text Articles in Physical Sciences and Mathematics

A Search For Enhanced Very High Energy Gamma-Ray Emission From The 2013 March Crab Nebula Flare, P. T. Reynolds, Et Al Dec 2013

A Search For Enhanced Very High Energy Gamma-Ray Emission From The 2013 March Crab Nebula Flare, P. T. Reynolds, Et Al

Physical Sciences Publications

In 2013 March, a flaring episode from the Crab Nebula lasting ~2 weeks was detected by Fermi-LAT (Large Area Telescope on board the Fermi Gamma-ray Space Telescope). The Very Energetic Radiation Imaging Telescope Array System (VERITAS) provides simultaneous observations throughout this period. During the flare, Fermi-LAT detected a 20 fold increase in flux above the average synchrotron flux >100 MeV seen from the Crab Nebula. Simultaneous measurements with VERITAS are consistent with the non-variable long-term average Crab Nebula flux at TeV energies. Assuming a linear correlation between the very high energy flux change >1 TeV and the flux …

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Long Term Observations Of B2 1215+30 With Veritas, E. Aliu, S. Archambault, T. Arlen, T. Aune, M. Beilicke, W. Benbow, R. Bird, A. Bouvier, J. H. Buckley, V. Bugaev, A. Cesarini, L. Ciupik, M. P. Connolly, W. Cui, J. Dumm, M. Errando, A. Falcone, S. Federici, Q. Feng, J. P. Finley, P. Fortin, L. Fortson, A. Furniss, N. Galante, L. Gerard, G. H. Gillanders, S. Griffin, J. Grube, G. Gyuk, D. Hanna, J. Holder, G. Hughes, T. B. Humensky, P. Kaaret, M. Kertzman, Y. Khassen, D. Kieda, H. Krawczynski, F. Krennrich, M. J. Lang, A. S. Madhavan, G. Maier, P. Majumdar, S. Mcarthur, A. Mccann, P. Moriarty, R. Mukherjee, D. Nieto, A. O’Faolain De Bhroithe, P. T. Reynolds, Et Al Dec 2013

Long Term Observations Of B2 1215+30 With Veritas, E. Aliu, S. Archambault, T. Arlen, T. Aune, M. Beilicke, W. Benbow, R. Bird, A. Bouvier, J. H. Buckley, V. Bugaev, A. Cesarini, L. Ciupik, M. P. Connolly, W. Cui, J. Dumm, M. Errando, A. Falcone, S. Federici, Q. Feng, J. P. Finley, P. Fortin, L. Fortson, A. Furniss, N. Galante, L. Gerard, G. H. Gillanders, S. Griffin, J. Grube, G. Gyuk, D. Hanna, J. Holder, G. Hughes, T. B. Humensky, P. Kaaret, M. Kertzman, Y. Khassen, D. Kieda, H. Krawczynski, F. Krennrich, M. J. Lang, A. S. Madhavan, G. Maier, P. Majumdar, S. Mcarthur, A. Mccann, P. Moriarty, R. Mukherjee, D. Nieto, A. O’Faolain De Bhroithe, P. T. Reynolds, Et Al

Physical Sciences Publications

We report on VERITAS observations of the BL Lac object B2 1215+30 between 2008 and 2012. During this period, the source was detected at very high energies (VHEs; E > 100 GeV) by VERITAS with a significance of 8.9σ and showed clear variability on timescales larger than months. In 2011, the source was found to be in a relatively bright state and a power-law fit to the differential photon spectrum yields a spectral index of 3.6 ± 0.4stat ± 0.3syst with an integral flux above 200 GeV of (8.0 ± 0.9stat ± 3.2syst) × 10−12 cm−2 s−1. No short term variability …

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Veritas Observations Of The Microquasar Cygnus X-3, P. T. Reynolds, Et Al Dec 2013

Veritas Observations Of The Microquasar Cygnus X-3, P. T. Reynolds, Et Al

Physical Sciences Publications

We report results from TeV gamma-ray observations of the microquasar Cygnus X-3. The observations were made with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) over a time period from 2007 June 11 to 2011 November 28. VERITAS is most sensitive to gamma rays at energies between 85 GeV and 30 TeV. The effective exposure time amounts to a total of about 44 hr, with the observations covering six distinct radio/X-ray states of the object. No significant TeV gamma-ray emission was detected in any of the states, nor with all observations combined. The lack of a positive signal, especially …

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Discovery Of A New Tev Gamma-Ray Source: Ver J0521+211, P. T. Reynolds, Veritas Oct 2013

Discovery Of A New Tev Gamma-Ray Source: Ver J0521+211, P. T. Reynolds, Veritas

Physical Sciences Publications

We report the detection of a new TeV gamma-ray source, VER J0521+211, based on observations made with the VERITAS imaging atmospheric Cherenkov Telescope Array. These observations were motivated by the discovery of a cluster of >30 GeV photons in the first year of Fermi Large Area Telescope observations. VER J0521+211 is relatively bright at TeV energies, with a mean photon flux of (1.93 ± 0.13stat ± 0.78sys) × 10–11 cm–2 s–1 above 0.2 TeV during the period of the VERITAS observations. The source is strongly variable on a daily timescale across all wavebands, from optical to TeV, with a peak …

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Multiwavelength Observations And Modeling Of 1es 1959+650 In A Low Flux State, P. T. Reynolds, Et. Al. Sep 2013

Multiwavelength Observations And Modeling Of 1es 1959+650 In A Low Flux State, P. T. Reynolds, Et. Al.

Physical Sciences Publications

We report on the VERITAS observations of the high-frequency peaked BL Lac object 1ES 1959+650 in the period 2007-2011. This source is detected at TeV energies by VERITAS at 16.4 standard deviation (σ) significance in 7.6 hr of observation in a low flux state. A multiwavelength spectral energy distribution (SED) is constructed from contemporaneous data from VERITAS, Fermi-LAT, RXTE PCA, and Swift UVOT. Swift XRT data is not included in the SED due to a lack of simultaneous observations with VERITAS. In contrast to the orphan γ-ray flare exhibited by this source in 2002, the X-ray flux of the source …

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Discovery Of Tev Gamma-Ray Emission From Cta 1 By Veritas, P. T. Reynolds, Et. Al. Feb 2013

Discovery Of Tev Gamma-Ray Emission From Cta 1 By Veritas, P. T. Reynolds, Et. Al.

Physical Sciences Publications

We report the discovery of TeV gamma-ray emission coincident with the shell-type radio supernova remnant (SNR) CTA 1 using the VERITAS gamma-ray observatory. The source, VER J0006+729, was detected as a 6.5 standard deviation excess over background and shows an extended morphology, approximated by a two-dimensional Gaussian of semimajor (semiminor) axis 0fdg30 (0fdg24) and a centroid 5' from the Fermi gamma-ray pulsar PSR J0007+7303 and its X-ray pulsar wind nebula (PWN). The photon spectrum is well described by a power-law dN/dE = N 0(E/3 TeV)–Γ, with a differential spectral index of Γ = 2.2 ± 0.2stat ± 0.3sys, and normalization …

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Rapid Tev Gamma-Ray Flaring Of Bl Lacertae, P. T. Reynolds, Veritas Jan 2013

Rapid Tev Gamma-Ray Flaring Of Bl Lacertae, P. T. Reynolds, Veritas

Physical Sciences Publications

We report on the detection of a very rapid TeV gamma-ray flare from BL Lacertae on 2011 June 28 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The flaring activity was observed during a 34.6 minute exposure, when the integral flux above 200 GeV reached (3.4 ± 0.6) × 10–6 photons m–2 s–1, roughly 125% of the Crab Nebula flux measured by VERITAS. The light curve indicates that the observations missed the rising phase of the flare but covered a significant portion of the decaying phase. The exponential decay time was determined to be 13 ± 4 minutes, …

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