1. The Cherenkov Telescope Array sensitivity to the transient skyValentina Fioretti, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, published scientific conference contribution Abstract: The Cherenkov Telescope Array (CTA) will be able to perform unprecedented observations of the transient very high-energy sky. An on-line science alert generation (SAG) pipeline, with a required 30 second latency, will allow the discovery or follow-up of gamma ray bursts (GRBs) and flaring emission from active galactic nuclei, galactic compact objects and electromagnetic counterparts of gravitational waves or neutrino messengers. The CTA sensitivity for very short exposures does not only depend on the technological performance of the array (e.g. effective area, background discrimination efficiency). The algorithms to evaluate the significance of the detection also define the sensitivity, together with their computational efficiency in order to satisfy the SAG latency requirements. We explore the aperture photometry and likelihood analysis techniques, and the associated parameters (e.g. on-source to off-source exposure ratio, minimum number of required signal events), defining the CTA ability to detect a significant signal at short exposures. The resulting CTA differential flux sensitivity as a function of the observing time, obtained using the latest Monte Carlo simulations, is compared to the sensitivities of Fermi–LAT and current-generation IACTs obtained in the overlapping energy ranges.
Keywords: very-high-energy gamma rays, Cherenkov Telescope Array (CTA) Observatory, transient astrophysical sources, gamma-ray bursts, active galactic nuclei
Published in RUNG: 15.11.2024; Views: 302; Downloads: 6
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2. The transient program of the Cherenkov Telescope ArrayFabian Schűssler, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, published scientific conference contribution Abstract: The Cherenkov Telescope Array (CTA) is the next generation high-energy gamma-ray
observatory. It will improve the sensitivity of current instruments up to an order of magnitude, while providing energy coverage for photons from 20 GeV to at least 300 TeV to reach high redshifts and extreme accelerators and will give access to the shortest time-scale phenomena. CTA is thus a uniquely powerful instrument for the exploration of the violent and variable universe.
The ability to probe short timescales at the highest energies will allow CTA to explore the
connection between accretion and ejection phenomena surrounding compact objects, investigate the processes occurring in relativistic outflows, and open up significant phase space for serendipitous discoveries. Aiming at playing a central role in the era of multi-messenger astrophysics, the CTA Transient program includes follow-up observations of a broad range of multi-wavelength and multi-messenger alerts, ranging from Galactic compact object binary systems to novel phenomena like Fast Radio Bursts. A promising case is that of gamma-ray bursts (GRBs), where CTA will for the first time enable high-statistics measurements above ∼ 10 GeV, probing new spectral components and shedding light on the physical processes at work in these systems. Dedicated programs searching for very-high-energy (VHE) gamma-ray counterparts to gravitational waves and high-energy neutrinos complete the CTA transients program.
This contribution will introduce and outline the CTA Transients program. We will provide an overview of the various science topics and discuss the links to multi-messenger and
multi-wavelength observations.
Keywords: very-high-energy (VHE) gamma rays, the Cherenkov Telescope Array (CTA) Observatory, transient astrophysical phenomena, relativistic outflows, gamma-ray bursts
Published in RUNG: 12.11.2024; Views: 241; Downloads: 4
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3. Fermi-GBM discovery of GRB 221009A : an extraordinarily bright GRB from onset to afterglowS. Lesage, P. Veres, M. S. Briggs, A. Goldstein, D. Kocevski, E. Burns, C. A. Wilson-Hodge, P. N. Bhat, D. Huppenkothen, Gabrijela Zaharijas, 2023, original scientific article Keywords: gamma-ray bursts, GRB 221009A, cosmic ray astronomy
Published in RUNG: 15.01.2024; Views: 1283; Downloads: 5
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4. 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, published scientific conference contribution Abstract: 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.
Keywords: very-high-energy gamma-ray astronomy, Cherenkov Telescope Array, CTA sensitivity, gamma-ray bursts, POpulation Synthesis Theory Integrated project for very high-energy emission
Published in RUNG: 04.12.2023; Views: 1821; Downloads: 6
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5. 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, published scientific conference contribution Abstract: 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.
Keywords: very-high-energy gamma-ray astronomy, Cherenkov Telescope Array, CTA sensitivity, gamma-ray bursts, population Synthesis Theory, very high-energy emission
Published in RUNG: 04.12.2023; Views: 2586; Downloads: 3
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6. Chasing gravitational waves with the Cherenkov Telescope ArrayJ. G. Green, Saptashwa Bhattacharyya, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, published scientific conference contribution Abstract: The detection of gravitational waves (GWs) from a binary neutron star (BNS) merger by Advanced
LIGO and Advanced Virgo (GW170817), along with the discovery of the electromagnetic counterparts
of this GW event, ushered in a new era of multimessenger astronomy, providing the first
direct evidence that BNS mergers are progenitors of short gamma-ray bursts (GRBs). Such events
may also produce very-high-energy (VHE, > 100 GeV) photons which have yet to be detected
in coincidence with a GW signal. The Cherenkov Telescope Array (CTA) is a next-generation
VHE observatory which aims to be indispensable in this search, with an unparalleled sensitivity
and ability to slew anywhere on the sky within a few tens of seconds. Achieving such a feat
will require a comprehensive real-time strategy capable of coordinating searches over potentially
very large regions of the sky. This work will evaluate and provide estimations on the number of
GW-CTA events determined from simulated BNS systems and short GRBs, considering both on and
off-axis emission. In addition, we will present and discuss the prospects of potential follow-up
strategies with CTA.
Keywords: gravitational waves, binary neutron star merger, short gamma-ray bursts
Published in RUNG: 15.09.2023; Views: 1775; Downloads: 5
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7. Catalog of long-term transient sources in the first 10 yr of Fermi-LAT dataL. Baldini, J. Ballet, D. Bastieri, J. Becerra Gonzalez, R. Bellazzini, A. Berretta, E. Bissaldi, R. D. Blandford, E. D. Bloom, Gabrijela Zaharijas, 2021, original scientific article Keywords: high energy astrophysics, active galactic nuclei, gamma-ray bursts, solar flares, solar gamma-ray emission
Published in RUNG: 17.02.2022; Views: 2537; Downloads: 42
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8. Multi-messenger astrophysics with THESEUS in the 2030sRiccardo Ciolfi, Giulia Stratta, Marica Branchesi, Bruce Gendre, Stefan Grimm, Jan Harms, Gavin Paul Lamb, Antonio Martin-Carrillo, Ayden McCann, Andreja Gomboc, 2021, original scientific article Keywords: multi-messenger astrophysics, Gamma-ray bursts, compact binary merger, Kilonova
Published in RUNG: 02.11.2021; Views: 2597; Downloads: 0
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9. Exploration of the high-redshift universe enabled by THESEUSNial R. Tanvir, E. Le Floc'h, L. Christensen, J. Caruana, R. Salvaterra, Giancarlo Ghirlanda, B. Ciardi, U. Maio, V. D'Odorico, Andreja Gomboc, 2021, original scientific article Keywords: reionization, Gamma-ray bursts, star forming galaxies, abundances
Published in RUNG: 02.11.2021; Views: 2330; Downloads: 0
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10. Synergies of THESEUS with the large facilities of the 2030s and guest observer opportunitiesP. Rosati, S. Basa, A. W. Blain, E. Bozzo, Marica Branchesi, L. Christensen, A. Ferrara, Andreja Gomboc, P. T. O'Brien, J. P. Osborne, 2021, original scientific article Keywords: multi-messenger astrophysics, Gamma-ray bursts, X-ray sources, gravitation wave sources
Published in RUNG: 02.11.2021; Views: 2545; Downloads: 0
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