1. Search for point sources of ultra-high-energy photons with the Telescope Array surface detectorR.U. Abbasi, Jon Paul Lundquist, 2020, original scientific article Abstract: The surface detector (SD) of the Telescope Array (TA) experiment allows us to detect indirectly photons with energies of the order of 10^18 eV and higher, and to separate photons from the cosmic ray background. In this paper, we present the results of a blind search for point sources of ultra-high-energy (UHE) photons in the Northern sky using the TA SD data. The photon-induced extensive air showers are separated from the hadron-induced extensive air shower background by means of a multivariate classifier based upon 16 parameters that characterize the air shower events. No significant evidence for the photon point sources is found. The upper limits are set on the flux of photons from each particular direction in the sky within the TA field of view, according to the experiment’s angular resolution for photons. The average 95 per cent confidence level upper-limits for the point-source flux of photons with energies greater than 10^18, 10^18.5, 10^19, 10^19.5 and 10^20 eV are 0.094, 0.029, 0.010, 0.0073 and 0.0058 km−2yr−1, respectively. For energies higher than 10^18.5 eV, the photon point-source limits are set for the first time. Numerical results for each given direction in each energy range are provided as a supplement to this paper.
Keywords: methods: data analysis, cosmic rays, gamma-rays: general
Published in RUNG: 29.04.2020; Views: 3803; Downloads: 0
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2. Testing a Reported Correlation between Arrival Directions of Ultra-high-energy Cosmic Rays and a Flux Pattern from nearby Starburst Galaxies using Telescope Array DataR.U. Abbasi, Jon Paul Lundquist, 2018, original scientific article Abstract: The Pierre Auger Collaboration (Auger) recently reported a correlation between the arrival directions of cosmic rays with energies above 39 EeV and the flux pattern of 23 nearby starburst galaxies (SBGs). In this Letter, we tested the same hypothesis using cosmic rays detected by the Telescope Array experiment (TA) in the 9-year period from May 2008 to May 2017. Unlike the Auger analysis, we did not optimize the parameter values but kept them fixed to the best-fit values found by Auger, namely 9.7% for the anisotropic fraction of cosmic rays assumed to originate from the SBGs in the list and 12.9◦ for the angular scale of the correlations. The energy threshold we adopted is 43 EeV, corresponding to 39 EeV in Auger when taking into account the energy-scale difference between two experiments. We find that the TA data is compatible with isotropy to within 1.1σ and with the Auger result to within 1.4σ, meaning that it is not capable to discriminate between these two hypotheses.
Keywords: astroparticle physics, cosmic rays, galaxies: starburst, methods: data analysis
Published in RUNG: 27.04.2020; Views: 4289; Downloads: 157
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4. An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray SourcesA. Aab, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Darko Veberič, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2018, original scientific article Keywords: astroparticle physics, cosmic rays, active galaxies, starburst galaxies, data analysis methods
Published in RUNG: 14.02.2018; Views: 4735; Downloads: 0
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