The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
N Bautistaelivar - One of the best experts on this subject based on the ideXlab platform.
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sensitivity of the high altitude water cherenkov detector to sources of multi tev Gamma Rays
Astroparticle Physics, 2013Co-Authors: A U Abeysekara, R Alfaro, C Alvarez, J C Arteagavelazquez, H Ayala A Solares, J D Alvarez, R Arceo, A S Barber, B M Baughman, N BautistaelivarAbstract:Abstract The High Altitude Water Cherenkov (HAWC) observatory is an array of large water Cherenkov detectors sensitive to Gamma Rays and hadronic cosmic Rays in the energy band between 100 GeV and 100 TeV. The observatory will be used to measure high-energy protons and cosmic Rays via detection of the energetic secondary particles reaching the ground when one of these particles interacts in the atmosphere above the detector. HAWC is under construction at a site 4100 meters above sea level on the northern slope of the volcano Sierra Negra, which is located in central Mexico at 19 ° N latitude. It is scheduled for completion in 2014. In this paper we estimate the sensitivity of the HAWC instrument to point-like and extended sources of Gamma Rays. The source fluxes are modeled using both unbroken power laws and power laws with exponential cutoffs. HAWC, in one year, is sensitive to point sources with integral power-law spectra as low as 5 × 10 - 13 cm - 2 sec - 1 above 2 TeV (approximately 50 mCrab) over 5 sr of the sky. This is a conservative estimate based on simple event parameters and is expected to improve as the data analysis techniques are refined. We discuss known TeV sources and the scientific contributions that HAWC can make to our understanding of particle acceleration in these sources.
John F Beacom - One of the best experts on this subject based on the ideXlab platform.
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role of line of sight cosmic ray interactions in forming the spectra of distant blazars in tev Gamma Rays and high energy neutrinos
The Astrophysical Journal, 2011Co-Authors: Warren Essey, Oleg Kalashev, Alexander Kusenko, John F BeacomAbstract:Active galactic nuclei (AGNs) can produce both Gamma Rays and cosmic Rays. The observed high-energy Gamma-ray signals from distant blazars may be dominated by secondary Gamma Rays produced along the line of sight by the interactions of cosmic-ray protons with background photons. This explains the surprisingly low attenuation observed for distant blazars, because the production of secondary Gamma Rays occurs, on average, much closer to Earth than the distance to the source. Thus, the observed spectrum in the TeV range does not depend on the intrinsic Gamma-ray spectrum, while it depends on the output of the source in cosmic Rays. We apply this hypothesis to a number of sources and, in every case, we obtain an excellent fit, strengthening the interpretation of the observed spectra as being due to secondary Gamma Rays. We explore the ramifications of this interpretation for limits on the extragalactic background light and for the production of cosmic Rays in AGNs. We also make predictions for the neutrino signals, which can help probe the acceleration of cosmic Rays in AGNs.
W Benbow - One of the best experts on this subject based on the ideXlab platform.
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detection of pulsed Gamma Rays above 100 gev from the crab pulsar
Science, 2011Co-Authors: E Aliu, T Arlen, T Aune, M Beilicke, W Benbow, A Bouvier, S M Bradbury, J H Buckley, V Bugaev, K L ByrumAbstract:We report the detection of pulsed Gamma Rays from the Crab pulsar at energies above 100 giga–electron volts (GeV) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) array of atmospheric Cherenkov telescopes. The detection cannot be explained on the basis of current pulsar models. The photon spectrum of pulsed emission between 100 mega–electron volts and 400 GeV is described by a broken power law that is statistically preferred over a power law with an exponential cutoff. It is unlikely that the observation can be explained by invoking curvature radiation as the origin of the observed Gamma Rays above 100 GeV. Our findings require that these Gamma Rays be produced more than 10 stellar radii from the neutron star.
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fast variability of tera electron volt Gamma Rays from the radio galaxy m87
Science, 2006Co-Authors: F Aharonian, A G Akhperjanian, A R Bazerbachi, K Bernlohr, M Beilicke, W Benbow, D Berge, O Bolz, C Boisson, V BorrelAbstract:The detection of fast variations of the TeV (10^12 eV) Gamma-ray flux, on time-scales of days, from the nearby radio galaxy M 87 is reported. These variations are ~10 times faster than that observed in any other waveband and imply a very compact emission region with a dimension similar to the Schwarzschild radius of the central black hole. We thus can exclude several other sites and processes of the Gamma-ray production. The observations confirm that TeV Gamma-Rays are emitted by extragalactic sources other than blazars, where jets are not relativistically beamed towards the observer.
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very high energy Gamma Rays from the direction of sagittarius a
Web Science, 2004Co-Authors: F Aharonian, A G Akhperjanian, A R Bazerbachi, K Bernlohr, M Beilicke, W Benbow, D Berge, P Berghaus, O Bolz, C BoissonAbstract:We report the detection of a point-like source of very high energy (VHE) Gamma-Rays coincident within 1' of Sgr A*, obtained with the H.E.S.S. array of Cherenkov telescopes. The Gamma-Rays exhibit a power-law energy spectrum with a spectral index of -2.2 +/- 0.09 +/- 0.15 and a flux above the 165 GeV threshold of (1.82 +/- 0.22) \times 10^{-7} m^{-2} s^{-1}. The measured flux and spectrum differ substantially from recent results reported in particular by the CANGAROO collaboration.
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observation of tev Gamma Rays from the crab nebula with milagro using a new background rejection technique
The Astrophysical Journal, 2003Co-Authors: R Atkins, W Benbow, D Berley, E Blaufuss, J Bussons, D G Coyne, R S Delay, T DeyoungAbstract:The recent advances in TeV Gamma-ray astronomy are largely the result of the ability to differentiate between extensive air showers generated by Gamma Rays and hadronic cosmic Rays. Air Cerenkov telescopes have developed and perfected the ‘‘ imaging ’’ technique over the past several decades. However, until now no background rejection method has been successfully used in an air shower array to detect a source of TeV Gamma Rays. We report on a method to differentiate hadronic air showers from electromagnetic air showers in the Milagro Gamma-ray observatory, based on the ability to detect the energetic particles in an extensive air shower. The technique is used to detect TeV emission from the Crab Nebula. The flux from the Crab Nebula is estimated to be 2:68ð� 0:42 stat � 1:4 sys Þ� 10 � 7 ðE=1 TeVÞ � 2:59 m � 2 s � 1 TeV � 1 , where the spectral index is assumed to be as given by the HEGRA collaboration. Subject headings: Gamma Rays: observations — instrumentation: detectors — ISM: individual (Crab Nebula) — stars: neutron — supernova remnants
Ghansham B. Dixit - One of the best experts on this subject based on the ideXlab platform.
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EMS, sodium azide and Gamma Rays induced meiotic anomalies in Delphinium malabaricum
2014Co-Authors: Firdose R. Kolar, Ghansham B. DixitAbstract:Meiotic cell division is a dynamic cellular process controlled by a large number of genes that act from premeiotic to postmeiotic mitosis. Mutation in these genes may cause anomalies that impair plant fertility. In this study, an attempt has therefore been made to understand the effects of ethyl methane sulfonate (EMS), sodium azide (SA) and Gamma Rays on the meiotic configuration of Delphinium malabaricum. The results demonstrated that the mutagens cause various types of cytological aberrations, such as univalents, chromatin bridges, laggards, fragments, stickiness and multinucleated cells. The maximum aberrations were found at higher doses/concentrations of the mutagens. The highest percentage of pollen mother cells showing abnormalities was induced by EMS followed by Gamma Rays and SA. The mutagen impact on chromosomal anomalies increased the frequency of pollen sterility.
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EMS, sodium azide and Gamma Rays induced meiotic anomalies in Delphinium malabaricum (Huth) Munz
Israel Journal of Plant Sciences, 2013Co-Authors: Firdose R. Kolar, Ghansham B. DixitAbstract:Meiotic cell division is a dynamic cellular process controlled by a large number of genes that act from premeiotic to postmeiotic mitosis. Mutation in these genes may cause anomalies that impair plant fertility. In this study, an attempt has therefore been made to understand the effects of ethyl methane sulfonate (EMS), sodium azide (SA) and Gamma Rays on the meiotic configuration of Delphinium malabaricum. The results demonstrated that the mutagens cause various types of cytological aberrations, such as univalents, chromatin bridges, laggards, fragments, stickiness and multinucleated cells. The maximum aberrations were found at higher doses/concentrations of the mutagens. The highest percentage of pollen mother cells showing abnormalities was induced by EMS followed by Gamma Rays and SA. The mutagen impact on chromosomal anomalies increased the frequency of pollen sterility.
T Deyoung - One of the best experts on this subject based on the ideXlab platform.
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observation of tev Gamma Rays from the crab nebula with milagro using a new background rejection technique
The Astrophysical Journal, 2003Co-Authors: R Atkins, W Benbow, D Berley, E Blaufuss, J Bussons, D G Coyne, R S Delay, T DeyoungAbstract:The recent advances in TeV Gamma-ray astronomy are largely the result of the ability to differentiate between extensive air showers generated by Gamma Rays and hadronic cosmic Rays. Air Cerenkov telescopes have developed and perfected the ‘‘ imaging ’’ technique over the past several decades. However, until now no background rejection method has been successfully used in an air shower array to detect a source of TeV Gamma Rays. We report on a method to differentiate hadronic air showers from electromagnetic air showers in the Milagro Gamma-ray observatory, based on the ability to detect the energetic particles in an extensive air shower. The technique is used to detect TeV emission from the Crab Nebula. The flux from the Crab Nebula is estimated to be 2:68ð� 0:42 stat � 1:4 sys Þ� 10 � 7 ðE=1 TeVÞ � 2:59 m � 2 s � 1 TeV � 1 , where the spectral index is assumed to be as given by the HEGRA collaboration. Subject headings: Gamma Rays: observations — instrumentation: detectors — ISM: individual (Crab Nebula) — stars: neutron — supernova remnants
