1. The Cherenkov Telescope ArrayDaniel Mazin, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, objavljeni znanstveni prispevek na konferenci Opis: The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory
for gamma-ray astronomy at very-high energies. It will be capable of detecting gamma rays in the energy range from 20 GeV to more than 300 TeV with unprecedented precision in energy and directional reconstruction. With more than 100 telescopes of three different types it will be located in the northern hemisphere at La Palma, Spain, and in the southern
at Paranal, Chile. CTA will be one of the largest astronomical infrastructures in the world with open data access and it will address questions in astronomy, astrophysics and fundamental physics in the next decades. In this presentation we will focus on the status
of the CTA construction, the status of the telescope prototypes and highlight some of the physics perspectives.
Ključne besede: very-high-energy gamma-ray astronomy, Cherenkov Telescope Array, CTA sensitivity, gamma-ray bursts, POpulation Synthesis Theory Integrated project for very high-energy emission
Objavljeno v RUNG: 04.12.2023; Ogledov: 84; Prenosov: 0
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2. POSyTIVE : a GRB population study for the Cherenkov Telescope ArrayMaria Grazia Bernardini, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, objavljeni znanstveni prispevek na konferenci Opis: One of the central scientific goals of the next-generation Cherenkov Telescope Array
(CTA) is the detection and characterization of gamma-ray bursts (GRBs). CTA will be sensitive to gamma rays with energies from about 20 GeV, up to a few hundred TeV.
The energy range below 1 TeV is particularly important for GRBs. CTA will allow exploration of this regime with a ground-based gamma-ray facility with unprecedented sensitivity.
As such, it will be able to probe radiation and particle acceleration mechanisms at work in GRBs. In this contribution, we describe POSyTIVE, the POpulation Synthesis Theory Integrated project for very high-energy emission. The purpose of the project is to make realistic predictions for the detection rates of GRBs with CTA, to enable studies
of individual simulated GRBs, and to perform preparatory studies for time-resolved
spectral analyses. The mock GRB population used by POSyTIVE is calibrated using the entire 40-year dataset of multi-wavelength GRB observations. As part of this project we explore theoretical models for prompt and afterglow emission of long and short GRBs,
and predict the expected radiative output. Subsequent analyses are performed
in order to simulate the observations with CTA, using the publicly available ctools and Gammapy frameworks. We present preliminary results of the design and implementation
of this project.
Ključne besede: very-high-energy gamma-ray astronomy, Cherenkov Telescope Array, CTA sensitivity, gamma-ray bursts, POpulation Synthesis Theory Integrated project for very high-energy emission
Objavljeno v RUNG: 04.12.2023; Ogledov: 68; Prenosov: 0
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3. Cherenkov Telescope Array Science : a multi-wavelength and multi-messenger perspectiveUlisses Barres de Almeida, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, objavljeni znanstveni prispevek na konferenci Opis: The Cherenkov Telescope Array (CTA) will be the major global observatory for
VHE gamma-ray astronomy over the next decade and beyond. It will be an explorer
of the extreme universe, with a broad scientific potential: from understanding the role of relativistic cosmic particles, to the search for dark matter. Covering photon energies from 20 GeV to 300 TeV, and with an angular resolution unique in the field, of about 1 arc min, CTA will improve on all aspects of the performance with respect to current instruments, surveying the high energy sky hundreds of times faster than previous TeV telescopes,
and with a much deeper view. The very large collection area of CTA makes it an important probe of transient phenomena. The first CTA telescope has just been inaugurated in the Canary Islands, Spain, and as more telescopes are added in the coming years, scientific operation will start. It is evident that CTA will have important synergies with many of the
new generation astronomical and astroparticle observatories. In this talk we will review
the CTA science case from the point of view of its synergies with other instruments and
facilities, highlighting the CTA needs in terms of external data, as well as the opportunities and strategies for cooperation to achieve the basic CTA science goals.
Ključne besede: very-high-energy gamma-ray astronomy, Cherenkov Telescope Array, CTA performances, transient VHE sources, CTA science
Objavljeno v RUNG: 04.12.2023; Ogledov: 96; Prenosov: 0
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4. The Cherenkov Telescope Array. Science Goals and Current StatusRene A. Ong, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, objavljeni znanstveni prispevek na konferenci (vabljeno predavanje) Opis: The Cherenkov Telescope Array (CTA) is the major ground-based gamma-ray observatory planned for the next decade and beyond. Consisting of two large atmospheric Cherenkov telescope arrays (one in the southern hemisphere and one in the northern
hemisphere), CTA will have superior angular resolution, a much wider energy range, and
approximately an order of magnitude improvement in sensitivity, as compared to existing instruments. The CTA science programme will be rich and diverse, covering cosmic particle acceleration, the astrophysics of extreme environments, and physics frontiers beyond the Standard Model. This paper outlines the science goals for CTA and covers the current status of the project.
Ključne besede: very-high-energy gamma-ray astronomy, Cherenkov Telescope Array (CTA), cosmic particle acceleration, astrophysics of extreme environments, physics beyond the Standard Model
Objavljeno v RUNG: 11.10.2023; Ogledov: 288; Prenosov: 7
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5. High-speed Video Camera Observations Associated with a Terrestrial Gamma-ray Flash at the Telescope Array DetectorR. Abbasi, Jon Paul Lundquist, 2023, objavljeni znanstveni prispevek na konferenci Opis: 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.
Ključne besede: Telescope Array, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, Lightning Mapping Array, gamma-ray flashes, photons
Objavljeno v RUNG: 10.10.2023; Ogledov: 275; Prenosov: 5
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6. Insight Into Lightning Initiation via Downward Terrestrial Gamma-ray Flash Observations at Telescope ArrayJ. Remington, Jon Paul Lundquist, 2022, objavljeni znanstveni prispevek na konferenci Opis: Due to the difficulty of direct measurement of the thunderstorm environment, in particular the electric field strengths, the initial stages of lightning breakdown remain mysterious. The 1994 discovery of Terrestrial Gamma-ray Flashes (TGFs) and their implications for megaVolt potentials within thunderclouds has proved to be a valuable source of information about the breakdown process.
The Telescope Array Surface Detector (TASD) --- a 700 km^2 scintillator array in Western Utah, U.S.A --- coupled with a lightning mapping array, fast sferic (field change) sensor and broadband interferometer, has provided unique insight into the properties of this energetic radiation and of lightning initiation in general. In particular, microsecond-scale timing comparisons have clearly established that downward TGFs occur during strong initial breakdown pulses (IBPs) of downward negative cloud-to-ground and intracloud flashes. In turn, the IBPs are produced by streamer-based fast negative breakdown.
Investigations into downward TGFs with the TASD have significantly evolved with recent upgrades to lightning instrumentation. A second state-of-the-art broadband interferometer allows high-resolution stereo observation of lightning development. A high-speed optical video camera, set to be deployed in Spring 2021, will allow simultaneous observation of the visual component of lightning responsible for TGF production. Finally, a suite of ground based static electric field mills will provide new information on the large-scale properties of the thunderstorms in which downward TGFs arise.
In this talk, we present the most recent TGF observations from the Telescope Array.
Ključne besede: Telescope Array, ground array, ultra-high energy, cosmic rays, photons, terrestrial gamma-ray flashes, gamma-rays, lightning
Objavljeno v RUNG: 02.10.2023; Ogledov: 285; Prenosov: 6
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7. Downward Terrestrial Gamma-ray Flashes at the Pierre Auger Observatory?R. Colalillo, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, objavljeni znanstveni prispevek na konferenci Opis: At the Pierre Auger Observatory, designed primarily to study ultra-high-energy cosmic rays, phenomena related to atmospheric electricity are also observed. Particularly, events have been detected with the surface detector, characterized by long-lasting signals (tens of microseconds) and event footprints much larger (up to 200 km2) than those produced by the highest energy cosmic rays. Moreover, some of them appear to be accompanied by smaller events occurring in the same area within about 1 ms and probably produced by the same phenomenon. A previously reported correlation with the World Wide Lightning Location Network, as well as the observation of very low-altitude clouds, confirm that such events are related to thunderstorms. An ad-hoc reconstruction points to high-energy particles being produced very close to the ground, suggesting that they originate from electrons accelerated to relativistic energies in strong electric fields inside low clouds, as is the case for terrestrial gamma-ray flashes above thunderstorms.
A clear explanation of the observed phenomenon is hindered by two facts. One is that the rate of such events, detected serendipitously, is very small (less than 2 events/year) and decreases further after optimization of the surface detector trigger for low-energy shower-events. The second is that most events show a puzzling lack of signals in the central part of the footprint. We have studied in detail both effects and will present such studies here. We developed a strategy for a dedicated trigger to enhance the detection efficiency for these events associated with atmospheric-electricity events.
Ključne besede: Pierre Auger Observatory, surface detection, ultra-high energy, cosmic rays, photons, electrons, gamma-ray flashes, lightning
Objavljeno v RUNG: 29.09.2023; Ogledov: 333; Prenosov: 6
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8. Sensitivity to keV-MeV dark matter from cosmic-ray scattering with current and the upcoming ground-based arrays CTA and SWGOIgor Reis, Saptashwa Bhattacharyya, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, objavljeni znanstveni prispevek na konferenci Opis: A wealth of astrophysical and cosmological observational evidence shows that the matter content of the universe is made of about 85% of non-baryonic dark matter. Huge experimental efforts have been deployed to look for the direct detection of dark matter via their scattering on target nucleons, their production in colliders, and their indirect detection via their annihilation products. Inelastic scattering of high-energy cosmic rays off dark matter particles populating the Milky Way halo would produce secondary gamma rays in the final state from the decay of the neutral pions produced in such interactions, providing a new avenue to probe dark matter properties. We compute here the sensitivity for H.E.S.S.-like observatory, a current-generation ground-based Cherenkov telescopes, to the expected gamma-ray flux from collisions of Galactic cosmic rays and dark matter in the center of the Milky Way. We also derive sensitivity prospects for the upcoming Cherenkov Telescope Array (CTA) and Southern Wide-field Gamma-ray Observatory (SWGO). The expected sensitivity allows us to probe a poorly-constrained range of dark matter masses so far, ranging from keV to sub-GeV, and provide complementary constraints on the dark matter-proton scattering cross section traditionally probed by deep underground direct dark matter experiments.
Ključne besede: Cherenkov Telescope Array, CTA, Southern Wide-field Gamma-ray Observatory, SWGO, dark matter
Objavljeno v RUNG: 26.09.2023; Ogledov: 270; Prenosov: 6
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9. Performance update of an event-type based analysis for the Cherenkov Telescope ArrayJuan Bernete, Saptashwa Bhattacharyya, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, objavljeni znanstveni prispevek na konferenci Opis: The Cherenkov Telescope Array (CTA) will be the next-generation observatory in the field of very-high-energy (20 GeV to 300 TeV) gamma-ray astroparticle physics. The traditional approach to data analysis in this field is to apply quality cuts, optimized using Monte Carlo simulations, on the data acquired to maximize sensitivity. Subsequent steps of the analysis typically use the surviving events to calculate one set of instrument response functions (IRFs) to physically interpret the results. However, an alternative approach is the use of event types, as implemented in experiments such as the Fermi-LAT. This approach divides events into sub-samples based on their reconstruction quality, and a set of IRFs is calculated for each sub-sample. The sub-samples are then combined in a joint analysis, treating them as independent observations. In previous works we demonstrated that event types, classified using Machine Learning methods according to their expected angular reconstruction quality, have the potential to significantly improve the CTA angular and energy resolution of a point-like source analysis. Now, we validated the production of event-type wise full-enclosure IRFs, ready to be used with science tools (such as Gammapy and ctools). We will report on the impact of using such an event-type classification on CTA high-level performance, compared to the traditional procedure.
Ključne besede: Cherenkov Telescope Array, CTA, very-high-energy gamma-ray astroparticle physics, instrument response functions, Machine Learning
Objavljeno v RUNG: 26.09.2023; Ogledov: 271; Prenosov: 6
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10. ctapipe – Prototype Open Event Reconstruction Pipeline for the Cherenkov Telescope ArrayMaximilian Linhoff, Saptashwa Bhattacharyya, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, objavljeni znanstveni prispevek na konferenci Opis: The Cherenkov Telescope Array Observatory (CTAO) is the next-generation ground-based gamma-ray observatory currently under construction. It will improve over the current genera-tion of imaging atmospheric Cherenkov telescopes (IACTs) by a factor of five to ten in sensitivity and it will be able to observe the whole sky from a combination of two sites: a northern site in La Palma, Spain, and a southern one in Paranal, Chile.
CTAO will also be the first open ground-based gamma-ray observatory. Accordingly, the CTAO data processing pipeline is developed as open-source software and ctapipe will be a core package therein. The event reconstruction pipeline accepts raw data of the telescopes and processes it to produce suitable input for the higher-level science tools. Its primary tasks include reconstructing the physical properties of each recorded air shower and providing the corresponding instrument response functions.
ctapipe is a python framework providing algorithms and command-line tools to facilitate raw data calibration, image extraction, image parametrization and event reconstruction. Its current main focus is the analysis of simulated data but it has also been successfully applied for the analysis of data obtained with the CTA prototype telescopes, and first science results have now been obtained by the LST-1 collaboration using ctapipe. A plugin system also allows the processing of non-CTA data.
Recent updates, including event reconstruction using machine learning and a new plugin system as well as the roadmap towards a 1.0 release will be presented.
Ključne besede: Cherenkov Telescope Array Observatory, CTAO, ground-based gamma-ray observatory, ctapipe
Objavljeno v RUNG: 26.09.2023; Ogledov: 263; Prenosov: 4
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