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1.
Searching for very-high-energy electromagnetic counterparts to gravitational-wave events with the Cherenkov Telescope Array
Barbara Patricelli, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci

Opis: The detection of electromagnetic (EM) emission following the gravitational wave (GW) event GW170817 opened the era of multi-messenger astronomy with GWs and provided the first direct evidence that at least a fraction of binary neutron star (BNS) mergers are progenitors of short Gamma-Ray Bursts (GRBs). GRBs are also expected to emit very-high energy (VHE, > 100 GeV) photons, as proven by the recent MAGIC and H.E.S.S. observations. One of the challenges for future multi-messenger observations will be the detection of such VHE emission from GRBs in association with GWs. In the next years, the Cherenkov Telescope Array (CTA) will be a key instrument for the EM follow-up of GW events in the VHE range, owing to its unprecedented sensitivity, rapid response, and capability to monitor a large sky area via scan-mode operation. We present the CTA GW follow-up program, with a focus on the searches for short GRBs possibly associated with BNS mergers. We investigate the possible observational strategies and we outline the prospects for the detection of VHE EM counterparts to transient GW events.
Ključne besede: Cherenkov Telescope Array, very-high energy photons, gravitational waves, gravitational wave counterparts
Objavljeno v RUNG: 19.09.2023; Ogledov: 67; Prenosov: 0
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2.
Sensitivity of the Cherenkov Telescope Array to emission from the gamma-ray counterparts of neutrino events
Olga Sergijenko, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci

Opis: We investigate the possibility of detection of the VHE gamma-ray counterparts to the neutrino astrophysical sources within the Neutrino Target of Opportunity (NToO) program of CTA using the populations simulated by the FIRESONG software to resemble the di˙use astrophysical neutrino flux measured by IceCube. We derive the detection probability for di˙erent zenith angles and geomagnetic field configurations. The di˙erence in detectability of sources between CTA-North and CTA-South for the average geomagnetic field is not substantial. We investigate the e˙ect of a higher night-sky background and the preliminary CTA Alpha layout on the detection probability.
Ključne besede: Cherenkov Telescope Array, VHE gamma-rays, neutrinos, Ice Cube, FIRESONG
Objavljeno v RUNG: 19.09.2023; Ogledov: 74; Prenosov: 1
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3.
HAWC J2227+610: a potential PeVatron candidate for the CTA in the northern hemisphere
Gaia Verna, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci

Opis: Recent observations of the gamma-ray source HAWC J2227+610 by Tibet AS+MD and LHAASO confirm the special interest of this source as a galactic PeVatron candidate in the northern hemi-sphere. HAWC J2227+610 emits Very High Energy (VHE) gamma-rays up to 500 TeV, from a region coincident with molecular clouds and significantly displaced from the nearby pulsar J2229+6114. Even if this morphology favours an hadronic origin, both leptonic or hadronic models can describe the current VHE gamma-ray emission. The morphology of the source is not well constrained by the present measurements and a better characterisation would greatly help the understanding of the underlying particle acceleration mechanisms. The Cherenkov Telescope Array (CTA) will be the future most sensitive Imaging Atmospheric Cherenkov Telescope and, thanks to its unprecedented angular resolution, could contribute to better constrain the nature of this source. The present work investigates the potentiality of CTA to study the morphology and the spectrum of HAWC J2227+610. For this aim, the source is simulated assuming the hadronic model proposed by the Tibet AS+MD collaboration, recently fitted on multi-wavelength data, and two spatial templates associated to the source nearby molecular clouds. Di˙erent CTA layouts and observation times are considered. A 3D map based analysis shows that CTA is able to significantly detect the extension of the source and to attribute higher detection significance to the simulated molecular cloud template compared to the alternative one. CTA data does not allow to disentangle the hadronic and the leptonic emission models. However, it permits to correctly reproduce the simulated parent proton spectrum characterized by a ∼ 500 TeV cuto˙.
Ključne besede: Cherenkov Telescope Array, HAWC J2227+610, very-high-energy gamma-rays
Objavljeno v RUNG: 19.09.2023; Ogledov: 67; Prenosov: 0
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4.
CTA sensitivity for probing cosmology and fundamental physics with gamma rays
Ievgen Vovk, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci

Opis: The Cherenkov Telescopic Array (CTA), the next-generation ground-based gamma-ray observatory, will have unprecedented sensitivity, providing answers to open questions in gamma-ray cosmology and fundamental physics. Using simulations of active galactic nuclei observations foreseen in the CTA Key Science Program, we find that CTA will measure gamma-ray absorption on the extragalactic background light with a statistical error below 15% up to the redshift of 2 and detect or establish limits on gamma halos induced by the intergalactic magnetic field of at least 0.3 pG. Extragalactic observations using CTA also demonstrate the potential for testing physics beyond the Standard Model. The best state-of-the-art constraints on the Lorentz invariance violation from astronomical gamma-ray observations will be improved at least two- to threefold. CTA will also probe the parameter space where axion-like particles can represent a significant proportion – if not all – of dark matter. Joint multiwavelength and multimessenger observations, carried out together with other future observatories, will further foster the growth of gamma-ray cosmology.
Ključne besede: Cherenkov Telescopic Array, ground-based gamma-ray observatory, beyond the Standard Model, extragalactic observations
Objavljeno v RUNG: 19.09.2023; Ogledov: 61; Prenosov: 0
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5.
Active Galactic Nuclei population studies with the Cherenkov Telescope Array
Anthony M. Brown, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci

Opis: The Cherenkov Telescope Array (CTA) observatory is the next generation of ground-based imaging atmospheric Cherenkov telescopes (IACTs). Building on the strengths of current IACTs, CTA is designed to achieve an order of magnitude improvement in sensitivity, with unprecedented angular and energy resolution. CTA will also increase the energy reach of IACTs, observing photons in the energy range from 20 GeV to beyond 100 TeV. These advances in performance will see CTA heralding in a new era for high-energy astrophysics, with the emphasis shifting from source discovery, to population studies and precision measurements. In this talk we discuss CTA’s ability to conduct source population studies of �-ray bright active galactic nuclei and how this ability will enhance our understanding on the redshift evolution of this dominant �-ray source class.
Ključne besede: Cherenkov Telescope Array, high-energy astrophysics, active galactic nuclei
Objavljeno v RUNG: 19.09.2023; Ogledov: 72; Prenosov: 0
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6.
The Cherenkov Telescope Array: layout, design and performance
Orel Gueta, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci

Opis: The Cherenkov Telescope Array (CTA) will be the next generation very-high-energy gamma-ray observatory. CTA is expected to provide substantial improvement in accuracy and sensitivity with respect to existing instruments thanks to a tenfold increase in the number of telescopes and their state-of-the-art design. Detailed Monte Carlo simulations are used to further optimise the number of telescopes and the array layout, and to estimate the observatory performance using updated models of the selected telescope designs. These studies are presented in this contribution for the two CTA stations located on the island of La Palma (Spain) and near Paranal (Chile) and for di˙erent operation and observation conditions.
Ključne besede: Cherenkov Telescope Array, very-high-energy gamma-ray observatory
Objavljeno v RUNG: 19.09.2023; Ogledov: 67; Prenosov: 0
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7.
Southern African Large Telescope Spectroscopy of BL Lacs for the CTA project
Eli Kasai, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci

Opis: n the last two decades, very-high-energy gamma-ray astronomy has reached maturity: over 200 sources have been detected, both Galactic and extragalactic, by ground-based experiments. At present, Active Galactic Nuclei (AGN) make up about 40% of the more than 200 sources detected at very high energies with ground-based telescopes, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth and three quarters of which are classified as high-frequency peaked BL Lac objects. One challenge to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGN to be detected with the future Cherenkov Telescope Array (CTA) observatory will have no spectroscopic redshifts, compromising the reliability of BL Lac population studies, particularly of their cosmic evolution. We started an effort in 2019 to measure the redshifts of a large fraction of the AGN that are likely to be detected with CTA, using the Southern African Large Telescope (SALT). In this contribution, we present two results from an on-going SALT program focused on the determination of BL Lac object redshifts that will be relevant for the CTA observatory.
Ključne besede: Cherenkov Telescope Array, very-high-energy gamma-ray astronomy, Active Galactic Nuclei, high-frequency peaked BL Lacs, Southern African Large Telescope
Objavljeno v RUNG: 18.09.2023; Ogledov: 77; Prenosov: 2
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8.
Exploring the population of Galactic very-high-energy γ-ray sources
Constantin Steppa, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci

Opis: At very high energies (VHE), the emission of γ rays is dominated by discrete sources. Due to the limited resolution and sensitivity of current-generation instruments, only a small fraction of the total Galactic population of VHE γ-ray sources has been detected significantly. The larger part of the population can be expected to contribute as a di˙use signal alongside emission originating from propagating cosmic rays. Without quantifying the source population, it is not possible to disentangle these two components. Based on the H.E.S.S. Galactic plane survey, a numerical approach has been taken to develop a model of the population of Galactic VHE γ-ray sources, which is shown to account accurately for the observational bias. We present estimates of the absolute number of sources in the Galactic Plane and their contribution to the total VHE γ-ray emission for five di˙erent spatial source distributions. Prospects for CTA and its ability to constrain the model are discussed. Finally, first results of an extension of our modelling approach using machine learning to extract more information from the available data set are presented.
Ključne besede: Cherenkov Telescope Array, very-high energy gamma-rays, gamma-ray sources
Objavljeno v RUNG: 18.09.2023; Ogledov: 81; Prenosov: 2
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9.
Prospects for Galactic transient sources detection with the Cherenkov Telescope Array
Alicia López-Oramas, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci

Opis: Several types of Galactic sources, like magnetars, microquasars, novae or pulsar wind nebulae flares, display transient emission in the X-ray band. Some of these sources have also shown emission at MeV–GeV energies. However, none of these Galactic transients have ever been detected in the very-high-energy (VHE; E>100 GeV) regime by any Imaging Air Cherenkov Telescope (IACT). The Galactic Transient task force is a part of the Transient Working group of the Cherenkov Telescope Array (CTA) Consortium. The task force investigates the prospects of detecting the VHE counterpart of such sources, as well as their study following Target of Opportunity (ToO) observations. In this contribution, we will show some of the results of exploring the capabilities of CTA to detect and observe Galactic transients; we assume di˙erent array configurations and observing strategies.
Ključne besede: Cherenkov Telescope Array, galactic transient sources, very-high energy gamma rays
Objavljeno v RUNG: 18.09.2023; Ogledov: 77; Prenosov: 2
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10.
Performance of the Cherenkov Telescope Array in the presence of clouds
Mario Pecimotika, Saptashwa BHATTACHARYYA, Barbara MARČUN, Judit PÉREZ ROMERO, Samo Stanič, Veronika VODEB, Serguei Vorobiov, Gabrijela ZAHARIJAS, Marko Zavrtanik, Danilo Zavrtanik, Miha ŽIVEC, 2021, objavljeni znanstveni prispevek na konferenci

Opis: The Cherenkov Telescope Array (CTA) is the future ground-based observatory for gamma-ray astronomy at very high energies. The atmosphere is an integral part of every Cherenkov telescope. Di˙erent atmospheric conditions, such as clouds, can reduce the fraction of Cherenkov photons produced in air showers that reach ground-based telescopes, which may a˙ect the performance. Decreased sensitivity of the telescopes may lead to misconstructed energies and spectra. This study presents the impact of various atmospheric conditions on CTA performance. The atmospheric transmission in a cloudy atmosphere in the wavelength range from 203 nm to 1000 nm was simulated for di˙erent cloud bases and di˙erent optical depths using the MODerate resolution atmospheric TRANsmission (MODTRAN) code. MODTRAN output files were used as inputs for generic Monte Carlo simulations. The analysis was performed using the MAGIC Analysis and Reconstruction Software (MARS) adapted for CTA. As expected, the e˙ects of clouds are most evident at low energies, near the energy threshold. Even in the presence of dense clouds, high-energy gamma rays may still trigger the telescopes if the first interaction occurs lower in the atmosphere, below the cloud base. A method to analyze very high-energy data obtained in the presence of clouds is presented. The systematic uncertainties of the method are evaluated. These studies help to gain more precise knowledge about the CTA response to cloudy conditions and give insights on how to proceed with data obtained in such conditions. This may prove crucial for alert-based observations and time-critical studies of transient phenomena.
Ključne besede: Cherenkov Telescope Array, very-high energy gamma rays, MODerate resolution atmospheric TRANsmission code, MAGIC Analysis and Reconstruction Software
Objavljeno v RUNG: 18.09.2023; Ogledov: 72; Prenosov: 2
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