1. Intermediate fluence downward terrestrial gamma ray flashes as observed by the Telescope Array Surface DetectorR. U. Abbasi, N. Kieu, P. R. Krehbiel, J. W. Belz, M. M. F. Saba, W. Rison, M. A. Stanley, D. Rodeheffer, D. Mazzucco, Jon Paul Lundquist, 2024, original scientific article Abstract: On 11 September 2021, two small thunderstorms developed over the Telescope Array Surface Detector (TASD) that produced an unprecedented number of six downward terrestrial gamma ray flashes (TGFs) within one‐hour timeframe. The TGFs occurred during the initial stage of negative cloud‐to‐ground flashes whose return strokes had increasingly large peak currents up to 223 kA, 147 GeV energy deposit in up to 25 1.2 km‐spaced surface detectors, and intermittent bursts of gamma‐rays with total durations up to 717 s. The analyses are based on observations recorded by the TASD network, complemented by data from a 3D lightning mapping array, broadband VHF interferometer, fast electric field change sensor, high‐speed video camera, and the National Lightning Detection Network. The TGFs of the final two flashes had gamma fluences of and 8, logarithmically bridging the gap between previous TASD and satellite‐based detections. The observations further emphasize the similarity between upward and downward TGF varieties, suggesting a common mechanism for their production.
Keywords: Telescope Array Surface Detector, terrestrial gamma ray flashes, 3D lightning mapping array, broadband VHF interferometer, fast electric field change sensor, high‐speed video camera, National Lightning Detection Network, TGF fluence measurement
Published in RUNG: 23.04.2025; Views: 74; Downloads: 0
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2. Gaia22dkvLb : a microlensing planet potentially accessible to radial-velocity characterizationZexuan Wu, Subo Dong, Tuan Yi, Zhuokai Liu, Kareem El-Badry, Andrew Gould, Łukasz Wyrzykowski, K. A. Rybicki, Mateusz Bronikowski, 2024, original scientific article Abstract: We report discovering an exoplanet from following up a microlensing event alerted by Gaia. The event Gaia22dkv is toward a disk source rather than the traditional bulge microlensing fields. Our primary analysis yields a Jovian planet with M_p = 0.59 (+0.15, -0.05) M_J at a projected orbital separation r_perpendicular = 1.4 (+0.8, -0.3) au, and the host is a ∼1.1 M⊙ turnoff star at ∼1.3 kpc. At r' ~= 14, the host is far brighter than any previously discovered microlensing planet host, opening up the opportunity to test the microlensing model with radial velocity (RV) observations. RV data can be used to measure the planet's orbital period and eccentricity, and they also enable searching for inner planets of the microlensing cold Jupiter, as expected from the "inner–outer correlation" inferred from Kepler and RV discoveries. Furthermore, we show that Gaia astrometric microlensing will not only allow precise measurements of its angular Einstein radius θ_E but also directly measure the microlens parallax vector and unambiguously break a geometric light-curve degeneracy, leading to the definitive characterization of the lens system.
Keywords: gravitational microlensing exoplanet detection, planetary astrophysics, astrophysics of galaxies, instrumentation astrophysics, methods for astrophysics, solar astrophysics, stellar astrophysics
Published in RUNG: 23.08.2024; Views: 1342; Downloads: 9
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3. Highlights from the Telescope Array ExperimentJ. Kim, Jon Paul Lundquist, 2023, published scientific conference contribution (invited lecture) Abstract: The Telescope Array (TA) is the largest ultra-high energy cosmic ray (UHECR) observatory in the Northern Hemisphere. Together with the TA Low Energy Extension (TALE), TA×4, and TALE infill detector, the TA measures the properties of UHECR-induced extensive air showers (EAS) in the energy region from 10^15 eV to over 10^20 eV. Each of these uses a hybrid system with an array of scintillators to sample the footprint of the EAS at the Earth’s surface along with telescopes that measure the fluorescence and Cherenkov light from the EAS. The statistics at the highest energies are being enhanced with the TA×4 detector, half completed but still under construction, which will quadruple the surface detector area with telescopes. The TALE infill surface detectors were recently deployed to further lower the hybrid energy threshold of TALE. We present the status of the experiment and recent results on the energy spectrum, mass composition, and anisotropy, including new features in the energy spectrum at about 10^19.2 eV and in the UHECR arrival direction anisotropy.
Keywords: Telescope Array, TALE, low energy extension, TAx4, indirect detection, hybrid detection, ground array, surface detection, fluorescence detection, cerenkov light, ultra-high energy, cosmic rays, energy spectrum, composition, anisotropy
Published in RUNG: 10.10.2023; Views: 2505; Downloads: 8
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4. Measurement of cosmic-ray proton and helium spectra from the ISS-CREAM experimentG. H. Choi, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: The Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM) experiment successfully recorded data for 539 days from Aug. 2017 to Feb. 2019. The ISS-CREAM instrument consists of a Silicon Charge Detector (SCD), carbon targets, a calorimeter (CAL), a top counting detector (TCD), a bottom counting detector (BCD), and a boronated scintillator detector (BSD). In this analysis, the SCD was used for the charge measurements. It comprises four layers, and each SCD layer is finely segmented with 2,688 silicon pixels to minimize charge misidentification due to the backscattered particles. The CAL was used for the energy measurements. It comprises 20 layers of tungsten/scintillating fibers. Each tungsten/scintillating-fiber layer consists of a 50 cm × 50 cm × 3.5 mm tungsten plate, followed by a layer of fifty 1 cm-wide 50 cm-long scintillating-fiber ribbons. The CAL also provides the incident cosmic-ray track and the high-energy trigger. For the low-energy trigger, the TCD and BCD were used. In this paper, we present the proton spectrum from the ISS-CREAM experiment in the energy range of 1.6 - 655 TeV and the preliminary helium spectrum in the energy range of 2.7 TeV - 1.1 PeV
Keywords: Telescope Array, TAx4, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2398; Downloads: 9
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5. Effect of optical properties of FDs on reconstruction analysisDaiki Sato, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, 2023, published scientific conference contribution Abstract: The TA experiment uses fluorescence telescopes to observe cosmic ray air showers. The telescope camera uses PMTs as Pixels. The telescope’s PMT pointing direction has an uncertainty of 0.1°, and more precise measurements of the telescope's optical properties are needed to more accurately reconstruct the cosmic ray air showers. We have developed the Opt-copter which is a light source mounted on a drone that can be flown within the telescope's field of view. Observational experiments with the Opt-copter have provided a more accurate analysis of the telescope viewing direction.
In this study, we estimate the effect of this measurement of accurate telescope viewing direction on the reconstruction of cosmic ray air showers.
Keywords: Telescope Array, indirect detection, fluorescence detection, ultra-high energy, cosmic rays, composition, calibration, Xmax
Published in RUNG: 10.10.2023; Views: 2572; Downloads: 9
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6. Effects of atmospheric transparency on Telescope Array air shower analysisK. Mizuno, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: The Telescope Array (TA) experiment continues to observe Ultra High Energy Cosmic Rays (UHECRs) both with its original TA detectors as well as with the new TAx4 expansion detectors. These observations employ Fluorescence Detectors (FDs) to capture the air shower induced by the primary UHECRs. The FD observes fluorescence light emitted from atmospheric nitrogen molecules excited by air shower particles. Observation of the FD extends over tens of kilometers, and the fluorescence light is attenuated by scattering from atmospheric molecules and aerosols during the propagation process. Seasonal dependence was found when evaluating the attenuation of fluorescence by aerosols. We will report on the effects of this seasonal dependence on TA air shower analysis.
Keywords: Telescope Array, TAx4, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2531; Downloads: 10
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7. Updates of the surface detector array of the TAx4 experimentEiji Kido, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: The TAx4 experiment plans to realize an Ultra High Energy Cosmic Rays (UHECR) detection area four times larger than that of the TA experiment. TAx4 will include five hundreds new surface detectors (SD) spaced at 2.08 km and two new fluorescence detectors (FD), which provides hybrid observation of UHECRs. We deployed 257 SDs in 2019 and completed building 2 FD stations in 2020, all operating stably. The data acquisition of the SDs is made via six communication towers, and inter-tower triggers have been recently implemented.
Keywords: Telescope Array, TAx4, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2025; Downloads: 11
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8. Anisotropies in the arrival direction distribution of ultra-high energy cosmic rays measured by the Telescope Array surface detectorJihyun Kim, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: Ultra-high energy cosmic rays (UHECRs) are extremely energetic, charged particles with energies greater than 10^18 eV, originating from outer space. We investigate anisotropic patterns in the arrival direction distribution of UHECRs to identify their source locations. The Telescope Array (TA) experiment, the largest UHECR observatory in the northern hemisphere, has observed evidence of two intermediate-scale anisotropies in UHECR arrival direction distributions: the TA Hotspot and the Perseus-Pisces supercluster excess. In this presentation, we will describe an oversampling analysis that we performed to find the excess of events using the data measured by the TA surface detector array. We will report the latest results of the TA Hotspot and Perseus-Pisces supercluster excesses.
Keywords: Telescope Array, TALE, low energy extension, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2102; Downloads: 6
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9. High-speed video camera observations associated with a terrestrial gamma-ray flash at the Telescope Array DetectorR. Abbasi, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: This work presents observations of the optical emission of a lightning flash in conjunction with a downward-directed Terrestrial Gamma-ray Flash (TGF) at the Telescope Array detector. Previously in ICRC-2021, we reported joint observations by the Telescope Array Surface Detector (TASD), the Lightning Mapping Array, a sferic sensor, and a broadband interferometer of particle showers in coincidence with lightning. These observations consisted of energetic showers of approximately less than 10-microsecond duration with footprints on the ground of 3-6 kilometers in diameter, originating in the first one to two milliseconds of downward lightning leaders and in coincidence with the initial breakdown pulses stage of negative cloud-to-ground lighting leaders. Scintillator waveform and simulation studies confirmed that these showers must consist primarily of gamma radiations.
In this work, we use the TASD detector, together with a high-speed video camera, in conjunction with multiple lightning instruments at the TASD site, to report on the optical emission associated with a downward-directed terrestrial gamma-ray flash. Results from this study allow us to further
the understanding of the initiation and propagation mechanism of terrestrial gamma-ray flashes. It will also further our ability to compare the most recent satellite optical emissions counterpart of upward-directed TGFs to that of downward-directed TGFs.
Keywords: Telescope Array, low energy extension, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2019; Downloads: 6
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10. Measurement of cosmic-ray energy spectrum with the TALE detector in hybrid modeH. Oshima, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, Jon Paul Lundquist, 2023, published scientific conference contribution Abstract: The TA Low-energy Extension (TALE) experiment extends the low-energy side of the TA experiment below 10^15 eV. A main objective of TALE is to study the transition from galactic to extragalactic cosmic rays. The TALE detector is a hybrid observatory composed of fluorescence telescopes and a surface detector array of scintillation counters. The surface detectors are arranged with inter-counter spacing of 400 and 600 meters, suitable for hybrid energy spectrum measurements in the low-energy region. We measured the energy spectrum using data collected during 429 hours of observation by the TALE hybrid detector. This energy spectrum measurement will play an important role in understanding the transition from cosmic rays of galactic origin to those of extragalactic origin.
Keywords: Telescope Array, TALE, low energy extension, indirect detection, hybrid detection
Published in RUNG: 10.10.2023; Views: 2618; Downloads: 6
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