Browsing by Author "Buckley, J. H."

Now showing 1 - 9 of 9
  • Thumbnail Image
    Item
    Discovery of Very-high-energy Emission from RGB J2243+203 and Derivation of Its Redshift Upper Limit
    (IOP Publishing, 2017-11-10) Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Brose, R.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Cerruti, M.; Connolly, M. P.; Cui, W.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Huetten, M.; Hanna, D.; Hervet, O.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; Maier, G.; McArthur, S.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Brien, S.; Ong, R. A.; Otte, A. N.; Park, N.; Petrashyk, A.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rulten, C.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Staszak, D.; Telezhinsky, I.; Tyler, J.; Vassiliev, V. V.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wilcox, P.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; Utah System of Higher Education; University of Utah; McGill University; Washington University (WUSTL); Harvard University; Smithsonian Institution; University of California System; University of California Los Angeles; University of Potsdam; Helmholtz Association; Deutsches Elektronen-Synchrotron (DESY); Ollscoil na Gaillimhe-University of Galway; Purdue University System; Purdue University; Purdue University West Lafayette Campus; Tsinghua University; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; University of Minnesota System; University of Minnesota Twin Cities; California State University System; California State University East Bay; Stevens Institute of Technology; University of California Santa Cruz; University of Delaware; Columbia University; University of Iowa; DePauw University; Iowa State University; University College Dublin; University System of Georgia; Georgia Institute of Technology; University of Chicago; Cork Institute of Technology; University of Alabama Tuscaloosa
    Very-high-energy (VHE; > 100 GeV) gamma-ray emission from the blazar RGB J2243+203 was discovered with the VERITAS Cherenkov telescope array, during the period between 2014 December 21 and 24. The VERITAS energy spectrum from this source can be fitted by a power law with a photon index of 4.6 +/- 0.5, and a flux normalization at 0.15 TeV of (6.3 +/- 1.1) x 10(-10) cm(-2) s(-1) TeV-1. The integrated Fermi-LAT flux from 1 to 100 GeV during the VERITAS detection is (4.1 +/- 0.8) x 10(-8) cm(-2) s(-1), which is an order of magnitude larger than the four-year-averaged flux in the same energy range reported in the 3FGL catalog, (4.0 +/- 0.1 x 10(-9) cm(-2) s(-1)). The detection with VERITAS triggered observations in the X-ray band with the Swift-XRT. However, due to scheduling constraints Swift-XRT observations were performed 67 hr after the VERITAS detection, rather than simultaneously with the VERITAS observations. The observed X-ray energy spectrum between 2 and 10 keV can be fitted with a power law with a spectral index of 2.7 +/- 0.2, and the integrated photon flux in the same energy band is (3.6 +/- 0.6) x 10(-13) cm(-2) s(-1). EBL-model-dependent upper limits of the blazar redshift have been derived. Depending on the EBL model used, the upper limit varies in the range from z < 0.9 to z < 1.1.
  • Thumbnail Image
    Item
    EXCEPTIONALLY BRIGHT TEV FLARES FROM THE BINARY LS I+61 degrees 303
    (IOP Publishing, 2016-01-19) Archambault, S.; Archer, A.; Aune, T.; Barnacka, A.; Benbow, W.; Bird, R.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickinson, H. J.; Dumm, J.; Eisch, J. D.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Flinders, A.; Fortin, P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Gyuk, G.; Huetten, M.; Hakansson, N.; Hanna, D.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Brien, S.; de Bhroithe, A. O'Faolain; Ong, R. A.; Otte, A. N.; Pandel, D.; Park, N.; Pelassa, V.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rousselle, J.; Rulten, C.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Vincent, S.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; McGill University; Washington University (WUSTL); University of California System; University of California Los Angeles; Harvard University; Smithsonian Astrophysical Observatory; Smithsonian Institution; University College Dublin; United States Department of Energy (DOE); Argonne National Laboratory; Iowa State University; University of Potsdam; Helmholtz Association; Deutsches Elektronen-Synchrotron (DESY); Ollscoil na Gaillimhe-University of Galway; Purdue University System; Purdue University; Purdue University West Lafayette Campus; University of Minnesota System; University of Minnesota Twin Cities; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; Utah System of Higher Education; University of Utah; California State University System; California State University East Bay; University of Delaware; Columbia University; University of California Santa Cruz; University of Iowa; DePauw University; University System of Georgia; Georgia Institute of Technology; Grand Valley State University; University of Chicago; Cork Institute of Technology; National Aeronautics & Space Administration (NASA); NASA Goddard Space Flight Center; University System of Maryland; University of Maryland College Park; University of Alabama Tuscaloosa
    The TeV binary system LS I +61 degrees 303 is known for its regular, non-thermal emission pattern that traces the orbital period of the compact object in its 26.5 day orbit around its B0 Ve star companion. The system typically presents elevated TeV emission around apastron passage with flux levels between 5% and 15% of the steady flux from the Crab Nebula (> 300 GeV). In this article, VERITAS observations of LS I + 61 degrees. 303 taken in late 2014 are presented, during which bright TeV flares around apastron at flux levels peaking above 30% of the Crab Nebula flux were detected. This is the brightest such activity from this source ever seen in the TeV regime. The strong outbursts have rise and fall times of less than a day. The short timescale of the flares, in conjunction with the observation of 10 TeV photons from LS I + 61 degrees 303 during the flares, provides constraints on the properties of the accelerator in the source.
  • Thumbnail Image
    Item
    Gamma-ray Observations of Tycho's Supernova Remnant with VERITAS and Fermi
    (IOP Publishing, 2017-02-06) Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Bourbeau, E.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Cerruti, M.; Connolly, M. P.; Cui, W.; Dwarkadas, V. V.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Griffin, S.; Huetten, M.; Hanna, D.; Holder, J.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Kumar, S.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Brien, S.; Ong, R. A.; Otte, A. N.; Park, N.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Slane, P.; Staszak, D.; Telezhinsky, I.; Trepanier, S.; Tyler, J.; Wakely, S. P.; Weinstein, A.; Weisgarber, T.; Wilcox, P.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; McGill University; Washington University (WUSTL); Harvard University; Smithsonian Institution; University of California System; University of California Los Angeles; Ollscoil na Gaillimhe-University of Galway; Purdue University System; Purdue University; Purdue University West Lafayette Campus; Tsinghua University; University of Chicago; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; University of Potsdam; University College Dublin; Cork Institute of Technology; Smithsonian Astrophysical Observatory; Iowa State University; University of Wisconsin System; University of Wisconsin Madison; University of Iowa; Utah System of Higher Education; University of Utah; DePauw University; Columbia University; University System of Georgia; Georgia Institute of Technology; University of Alabama Tuscaloosa
    High-energy gamma-ray emission from supernova remnants (SNRs) has provided a unique perspective for studies of Galactic cosmic-ray acceleration. Tycho's SNR is a particularly good target because it is a young, type Ia SNR that has been. well-studied over a wide range of energies and located in a relatively clean environment. Since the detection of gamma-ray emission from Tycho's SNR by VERITAS and Fermi-LAT, there have been several theoretical models proposed to explain its broadband emission and high-energy morphology. We report on an update to the gamma-ray measurements of Tycho's SNR with 147 hr of VERITAS and 84 months of Fermi-LAT observations, which represent about a factor of two increase in exposure over previously published data. About half of the VERITAS data benefited from a camera upgrade, which has made it possible to extend the TeV measurements toward lower energies. The TeV spectral index measured by VERITAS is consistent with previous results, but the expanded energy range softens a straight power-law fit. At energies higher than 400GeV, the power-law index is 2.92 +/- 0.42(stat) +/- 0.20(sys). It is also softer than the spectral index in the GeV energy range, 2.14 +/- 0.09(stat) +/- 0.02(sys), measured in this study using Fermi-LAT data. The centroid position of the gamma-ray emission is coincident with the center of the remnant, as well as with the centroid measurement of Fermi-LAT above 1 GeV. The results are consistent with an SNR shell origin of the emission, as many models assume. The updated spectrum points to a lower maximum particle energy than has been suggested previously.
  • Thumbnail Image
    Item
    A SEARCH FOR BRIEF OPTICAL FLASHES ASSOCIATED WITH THE SETI TARGET KIC 8462852
    (IOP Publishing, 2016-02-18) Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Buchovecky, M.; Buckley, J. H.; Byrum, K.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Christiansen, J. L.; Ciupik, L.; Cui, W.; Dickinson, H. J.; Eisch, J. D.; Errando, M.; Falcone, A.; Fegan, D. J.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortin, P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Gyuk, G.; Huetten, M.; Hakansson, N.; Hanna, D.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; Lin, T. T. Y.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Brien, S.; de Bhroithe, A. O'Faolain; Ong, R. A.; Otte, A. N.; Park, N.; Perkins, J. S.; Petrashyk, A.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Ratliff, G.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Vincent, S.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Williams, D. A.; Zitzer, B.; Utah System of Higher Education; University of Utah; McGill University; Washington University (WUSTL); Harvard University; Smithsonian Institution; University College Dublin; University of California System; University of California Los Angeles; United States Department of Energy (DOE); Argonne National Laboratory; Iowa State University; University of Potsdam; Helmholtz Association; Deutsches Elektronen-Synchrotron (DESY); California State University System; California Polytechnic State University San Luis Obispo; Purdue University System; Purdue University; Purdue University West Lafayette Campus; Columbia University; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; University of Minnesota System; University of Minnesota Twin Cities; California State University East Bay; Ollscoil na Gaillimhe-University of Galway; University of Delaware; Florida Institute of Technology; University of California Santa Cruz; University of Iowa; DePauw University; University System of Georgia; Georgia Institute of Technology; University of Chicago; National Aeronautics & Space Administration (NASA); NASA Goddard Space Flight Center; Cork Institute of Technology; University of Alabama Tuscaloosa
    The F-type star KIC. 8462852 has recently been identified as an exceptional target for search for extraterrestrial intelligence (SETI) observations. We describe an analysis methodology for optical SETI, which we have used to analyze nine hours of serendipitous archival observations of KIC. 8462852 made with the VERITAS gamma-ray observatory between 2009 and 2015. No evidence of pulsed optical beacons, above a pulse intensity at the Earth of approximately 1 photon m(-2), is found. We also discuss the potential use of imaging atmospheric Cherenkov telescope arrays in searching for extremely short duration optical transients in general.
  • Thumbnail Image
    Item
    A SEARCH FOR PULSATIONS FROM GEMINGA ABOVE 100 GeV WITH VERITAS
    (IOP Publishing, 2015-02-09) Aliu, E.; Archambault, S.; Archer, A.; Aune, T.; Barnacka, A.; Beilicke, M.; Benbow, W.; Bird, R.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dickinson, H. J.; Dumm, J.; Eisch, J. D.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortin, P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Kansson, N. H. A.; Hanna, D.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kertzman, M.; Kieda, D.; Krennrich, F.; Kumar, S.; Lang, M. J.; Lyutikov, M.; Madhavan, A. S.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nieto, D.; de Bhroithe, A. O'Faolain; Ong, R. A.; Otte, A. N.; Park, N.; Pohl, M.; Popkow, A.; Prokoph, H.; Pueschel, E.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Varlotta, A.; Vincent, S.; Wakely, S. P.; Weinstein, A.; Williams, D. A.; Zajczyk, A.; Zitzer, B.; Columbia University; Institut d'Estudis Espacials de Catalunya (IEEC); University of Barcelona; McGill University; Washington University (WUSTL); University of California System; University of California Los Angeles; Harvard University; Smithsonian Astrophysical Observatory; Smithsonian Institution; University College Dublin; United States Department of Energy (DOE); Argonne National Laboratory; Iowa State University; University of Potsdam; Helmholtz Association; Deutsches Elektronen-Synchrotron (DESY); Ollscoil na Gaillimhe-University of Galway; Purdue University System; Purdue University; Purdue University West Lafayette Campus; University of Minnesota System; University of Minnesota Twin Cities; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; University of California Santa Cruz; University of Iowa; University of Delaware; Utah System of Higher Education; University of Utah; DePauw University; University of Chicago; University System of Georgia; Georgia Institute of Technology; California State University System; California Polytechnic State University San Luis Obispo; Cork Institute of Technology; University of Alabama Tuscaloosa
    We present the results of 71.6 hr of observations of the Geminga pulsar (PSR J0633+1746) with the VERITAS very-high-energy gamma-ray telescope array. Data taken with VERITAS between 2007 November and 2013 February were phase-folded using a Geminga pulsar timing solution derived from data recorded by the XMM-Newton and Fermi-LAT space telescopes. No significant pulsed emission above 100 GeV is observed, and we report upper limits at the 95% confidence level on the integral flux above 135 GeV (spectral analysis threshold) of 4.0x10(-13) s(-1) cm(-2) and 1.7 x 10(-13) s(-1) cm(-2) for the two principal peaks in the emission profile. These upper limits, placed in context with phase-resolved spectral energy distributions determined from 5 yr of data from the Fermi-Large Area Telescope (LAT), constrain possible hardening of the Geminga pulsar emission spectra above similar to 50 GeV.
  • Thumbnail Image
    Item
    A SEARCH FOR VERY HIGH ENERGY GAMMA RAYS FROM THE MISSING LINK BINARY PULSAR J1023+0038 WITH VERITAS
    (IOP Publishing, 2016-11-08) Aliu, E.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Biteau, J.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dickinson, H. J.; Eisch, J. D.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Flinders, A.; Fortin, P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Gyuk, G.; Huetten, M.; Hakansson, N.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Lang, M. J.; Loo, A.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nguyen, T.; Nieto, D.; De Bhroithe, A. O'Faolain; Ong, R. A.; Otte, A. N.; Pandel, D.; Park, N.; Pelassa, V.; Petrashyk, A.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rulten, C.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Varlotta, A.; Vincent, S.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; Chernyakova, M.; Roberts, M. S. E.; Columbia University; McGill University; Washington University (WUSTL); Harvard University; Smithsonian Institution; University College Dublin; University of California System; University of California Santa Cruz; University of California Los Angeles; United States Department of Energy (DOE); Argonne National Laboratory; Iowa State University; University of Potsdam; Helmholtz Association; Deutsches Elektronen-Synchrotron (DESY); Ollscoil na Gaillimhe-University of Galway; Purdue University System; Purdue University; Purdue University West Lafayette Campus; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; Utah System of Higher Education; University of Utah; University of Minnesota System; University of Minnesota Twin Cities; California State University System; California State University East Bay; University of Delaware; University of Iowa; DePauw University; University System of Georgia; Georgia Institute of Technology; Grand Valley State University; University of Chicago; Cork Institute of Technology; University System of Maryland; University of Maryland College Park; Dublin City University; Dublin Institute for Advanced Studies; Eureka Scientific; University of Alabama Tuscaloosa
    The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259-63/LS 2883, making it an ideal candidate for the study of high-energy nonthermal emission. It has been the subject of multiwavelength campaigns following the disappearance of the pulsed radio emission in 2013 June, which revealed the appearance of an accretion disk around the neutron star. We present the results of very high energy (VHE) gamma-ray observations carried out by the Very Energetic Radiation Imaging Telescope Array System before and after this change of state. Searches for steady and pulsed emission of both data sets yield no significant gamma-ray signal above 100 GeV, and upper limits are given for both a steady and pulsed gamma-ray flux. These upper limits are used to constrain the magnetic field strength in the shock region of the PSR J1023+0038 system. Assuming that VHE gamma rays are produced via an inverse Compton mechanism in the shock region, we constrain the shock magnetic field to be greater than similar to 2 G before the disappearance of the radio pulsar and greater than similar to 10 G afterward.
  • Thumbnail Image
    Item
    TEV GAMMA-RAY OBSERVATIONS OF THE GALACTIC CENTER RIDGE BY VERITAS
    (IOP Publishing, 2016-04-22) Archer, A.; Benbow, W.; Bird, R.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Eisch, J. D.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Flinders, A.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Gyuk, G.; Hakansson, N.; Hanna, D.; Holder, J.; Humensky, T. B.; Huetten, M.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; McArthur, S.; McCann, A.; Meagher, K.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nieto, D.; Ong, R. A.; Park, N.; Pelassa, V.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Ratliff, G.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rousselle, J.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Vassiliev, V. V.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; Yusef-Zadeh, F.; Washington University (WUSTL); Harvard University; Smithsonian Institution; University College Dublin; University of California System; University of California Los Angeles; United States Department of Energy (DOE); Argonne National Laboratory; Iowa State University; University of Potsdam; Helmholtz Association; Deutsches Elektronen-Synchrotron (DESY); Ollscoil na Gaillimhe-University of Galway; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; Purdue University System; Purdue University; Purdue University West Lafayette Campus; Utah System of Higher Education; University of Utah; University of Minnesota System; University of Minnesota Twin Cities; California State University System; California State University East Bay; McGill University; University of Delaware; Columbia University; University of California Santa Cruz; University of Iowa; DePauw University; University System of Georgia; Georgia Institute of Technology; University of Chicago; Cork Institute of Technology; University System of Maryland; University of Maryland College Park; National Aeronautics & Space Administration (NASA); NASA Goddard Space Flight Center; Northwestern University; University of Alabama Tuscaloosa
    The Galactic Center ridge has been observed extensively in the past by both GeV and TeV gamma-ray instruments revealing a wealth of structure, including a diffuse component and the point sources G0.9+0.1 (a composite supernova remnant) and Sgr A* (believed to be associated with the supermassive black hole located at the center of our Galaxy). Previous very high energy (VHE) gamma-ray observations with the H.E.S.S.. experiment have also detected an extended TeV gamma-ray component along the Galactic plane in the >300 GeV gamma-ray regime. Here we report on observations of the Galactic Center ridge from 2010 to 2014 by the VERITAS telescope array in the >2 TeV energy range. From these observations we (1) provide improved measurements of the differential energy spectrum for Sgr A* in the >2 TeV gamma-ray regime, (2) provide a detection in the >2 TeV gamma-ray emission from the composite SNR G0.9+0.1 and an improved determination of its multi-TeV gamma-ray energy spectrum, and. (3) report on the detection of VER J1746-289, a localized enhancement of >2 TeV gamma-ray emission along the Galactic plane.
  • Thumbnail Image
    Item
    VERITAS and multiwavelength observations of the BL Lacertae object 1ES 1741+196
    (Oxford University Press, 2016-05-04) Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Biteau, J.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Christiansen, J. L.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dickinson, H. J.; Dumm, J.; Eisch, J. D.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Flinders, A.; Fortin, P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Gyuk, G.; Huetten, M.; Hanna, D.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Brien, S.; de Bhroithe, A. O'Faolain; Ong, R. A.; Otte, A. N.; Park, N.; Pelassa, V.; Petrashyk, A.; Petry, D.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Ratliff, G.; Reyes, L. C.; Reynolds, P. T.; Reynolds, K.; Richards, G. T.; Roache, E.; Rulten, C.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Vincent, S.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; Utah System of Higher Education; University of Utah; McGill University; Washington University (WUSTL); Harvard University; Smithsonian Institution; University College Dublin; University of California System; University of California Santa Cruz; University of California Los Angeles; United States Department of Energy (DOE); Argonne National Laboratory; Iowa State University; University of Potsdam; Helmholtz Association; Deutsches Elektronen-Synchrotron (DESY); California State University System; California Polytechnic State University San Luis Obispo; Purdue University System; Purdue University; Purdue University West Lafayette Campus; University of Minnesota System; University of Minnesota Twin Cities; Columbia University; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; California State University East Bay; University of Delaware; University of Iowa; DePauw University; University System of Georgia; Georgia Institute of Technology; University of Chicago; National Aeronautics & Space Administration (NASA); NASA Goddard Space Flight Center; University System of Maryland; University of Maryland College Park; University of Alabama Tuscaloosa
    We present results from multiwavelength observations of the BL Lacertae object 1ES 1741 + 196, including results in the very high energy gamma-ray regime using the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The VERITAS time-averaged spectrum, measured above 180 GeV, is well modelled by a power law with a spectral index of 2.7 +/- 0.7(stat) +/- 0.2(syst). The integral flux above 180 GeV is (3.9 +/- 0.8(stat) +/- 1.0(syst)) x 10(-8) m(-2) s(-1), corresponding to 1.6 per cent of the Crab nebula flux on average. The multiwavelength spectral energy distribution of the source suggests that 1ES 1741+196 is an extreme-high-frequency-peaked BL Lacertae object. The observations analysed in this paper extend over a period of six years, during which time no strong flares were observed in any band. This analysis is therefore one of the few characterizations of a blazar in a non-flaring state.
  • Thumbnail Image
    Item
    Very-High-Energy gamma-Ray Observations of the Blazar 1ES 2344+514 with VERITAS
    (Oxford University Press, 2017-07-17) Allen, C.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Bourbeau, E.; Brose, R.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Christiansen, J. L.; Connolly, M. P.; Cui, W.; Daniel, M. K.; Eisch, J. D.; Falcone, A.; Feng, Q.; Fernandez-Alonso, M.; Finley, J. P.; Fleischhack, H.; Flinders, A.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Huetten, M.; Hakansson, N.; Hanna, D.; Hervet, O.; Holder, J.; Hughes, G.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nguyen, T.; Nieto, D.; O'Brien, S.; de Bhroithe, A. O'Faolain; Ong, R. A.; Otte, A. N.; Park, N.; Petrashyk, A.; Pichel, A.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rovero, A. C.; Rulten, C.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Wakely, S. P.; Weinstein, A.; Wilhelm, A.; Williams, D. A.; California State University System; California Polytechnic State University San Luis Obispo; McGill University; Washington University (WUSTL); Harvard University; Smithsonian Institution; University of California System; University of California Los Angeles; University of Potsdam; Helmholtz Association; Deutsches Elektronen-Synchrotron (DESY); Iowa State University; Ollscoil na Gaillimhe-University of Galway; Purdue University System; Purdue University; Purdue University West Lafayette Campus; Tsinghua University; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; Instituto de Astronomia y Fisica del Espacio (IAFE); Utah System of Higher Education; University of Utah; University of Minnesota System; University of Minnesota Twin Cities; California State University East Bay; Stevens Institute of Technology; University of California Santa Cruz; University of Delaware; Columbia University; University of Iowa; DePauw University; University System of Georgia; Georgia Institute of Technology; University College Dublin; University of Chicago; Cork Institute of Technology; University of Alabama Tuscaloosa
    We present very-high-energy gamma-ray observations of the BL Lac object 1ES 2344+514 taken by the Very Energetic Radiation Imaging Telescope Array System between 2007 and 2015. 1ES 2344+514 is detected with a statistical significance above the background of 20.8 sigma in 47.2 h (livetime) of observations, making this the most comprehensive very-high-energy study of 1ES 2344+514 to date. Using these observations, the temporal properties of 1ES 2344+514 are studied on short and long times-scales. We fit a constant-flux model to nightly and seasonally binned light curves and apply a fractional variability test to determine the stability of the source on different time-scales. We reject the constant-flux model for the 2007-2008 and 2014-2015 nightly binned light curves and for the long-term seasonally binned light curve at the > 3 sigma level. The spectra of the time-averaged emission before and after correction for attenuation by the extragalactic background light are obtained. The observed time-averaged spectrum above 200 GeV is satisfactorily fitted (x(2)/NDF = 7.89/6) by a power-law function with an index Gamma = 2.46 +/- 0.06(stat) +/- 0.20(sys) and extends to at least 8 TeV. The extragalactic-backgroundlight-deabsorbed spectrum is adequately fit (x(2)/NDF = 6.73/6) by a power-law function with an index Gamma = 2.15 +/- 0.06(stat) +/- 0.20(sys) while an F-test indicates that the power law with an exponential cut-off function provides a marginally better fit (x(2)/NDF = 2.56/5) at the 2.1 sigma level. The source location is found to be consistent with the published radio location and its spatial extent is consistent with a point source.