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Opis: 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.
Ključne besede: very-high-energy (VHE) gamma rays, the Cherenkov Telescope Array (CTA) Observatory, transient astrophysical phenomena, relativistic outflows, gamma-ray bursts
Objavljeno v RUNG: 12.11.2024; Ogledov: 643; Prenosov: 5
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Opis: The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory for γ-ray astronomy at energies above 30 GeV. Thanks to its unique capabilities, CTA observations will address a plethora of open questions in astrophysics, ranging from the origin of cosmic messengers to the exploration of the frontiers of physics. In this note, we present a comprehensive sensitivity study to assess the potential of CTA to measure the γ-ray absorption on the extragalactic background light (EBL), to constrain or detect intergalactic magnetic fields (IGMFs), and probe physics beyond the standard model such as axion-like particles (ALPs) and Lorentz invariance violation (LIV), which could modify the γ-ray spectra features expected from EBL absorption. Our results suggest that CTA will have unprecedented sensitivity to detect IGMF signatures and will probe so-far unexplored regions of the LIV and ALP parameter space. Furthermore, an indirect measurement of the EBL and of its evolution will be performed with unrivaled precision.
Ključne besede: very-high-energy gamma rays, the Cherenkov Telescope Array (CTA) Observatory, extragalactic background light (EBL), intergalactic magnetic fields (IGMFs), axion-like particles (ALPs), Lorentz invariance violation (LIV)
Objavljeno v RUNG: 07.11.2024; Ogledov: 604; Prenosov: 5
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Opis: Approximately one hundred sources of very-high-energy (VHE) gamma rays are known in the Milky Way, detected with a combination of targeted observations and surveys. A survey of the entire Galactic Plane in the energy range from a few tens of GeV to a few hundred TeV has been proposed as a Key Science Project for the upcoming Cherenkov Telescope Array Observatory (CTAO). This article presents the status of the studies towards the Galactic Plane Survey (GPS). We build and make publicly available a sky model that combines data from recent observations of known gamma-ray emitters with state-of-the-art physically-driven models of synthetic populations of the three main classes of established Galactic VHE sources (pulsar wind nebulae, young and interacting supernova remnants, and compact binary systems), as well as of interstellar emission from cosmic-ray interactions in the Milky Way. We also perform an optimisation of the observation strategy (pointing pattern and scheduling) based on recent estimations of the instrument performance. We use the improved sky model and observation strategy to simulate GPS data corresponding to a total observation time of 1620 hours spread over ten years. Data are then analysed using the methods and software tools under development for real data. Under our model assumptions and for the realisation considered, we show that the GPS has the potential to increase the number of known Galactic VHE emitters by almost a factor of five. This corresponds to the detection of more than two hundred pulsar wind nebulae and a few tens of supernova remnants at average integral fluxes one order of magnitude lower than in the existing sample above 1 TeV, therefore opening the possibility to perform unprecedented population studies. The GPS also has the potential to provide new VHE detections of binary systems and pulsars, to confirm the existence of a hypothetical population of gamma-ray pulsars with an additional TeV emission component, and to detect bright sources capable of accelerating particles to PeV energies (PeVatrons). Furthermore, the GPS will constitute a pathfinder for deeper follow-up observations of these source classes. Finally, we show that we can extract from GPS data an estimate of the contribution to diffuse emission from unresolved sources, and that there are good prospects of detecting interstellar emission and statistically distinguishing different scenarios. Thus, a survey of the entire Galactic plane carried out from both hemispheres with CTAO will ensure a transformational advance in our knowledge of Galactic VHE source populations and interstellar emission.
Ključne besede: very-high-energy gamma rays, Cherenkov Telescope Array Observatory, CTAO Galactic Plane Survey, galactic cosmic rays, pulsar wind nebulae, supernova remnants, galactic PeVatrons, binary systems, diffuse emission
Objavljeno v RUNG: 28.10.2024; Ogledov: 779; Prenosov: 4
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Opis: Gamma rays serve as important messengers in modern astrophysics, offering insights into the most energetic processes in the cosmos. Advancements in gamma-ray astronomy, facilitated by international scientific collaboration, have expanded its reach and capabilities. The Fermi-Large Area Telescope (Fermi-LAT) has so far contributed immensely to our understanding of the gamma-ray sky at GeV energies, surveying numerous source classes. At the same time, ground-based observatories like H.E.S.S., MAGIC, VERITAS, HAWC, and LHASSO, enable the exploration of high-energy (HE) phenomena across various energy scales, reaching the PeV range. The collective data from Fermi-LAT and ground-based instruments provide a comprehensive picture of cosmic phenomena across diverse energy regimes. Efforts to catalog HE gamma-ray sources have resulted in the detection of several thousand sources at GeV, including Pulsar Wind Nebulae (PWNe), Supernova Remnants (SNRs), pulsars, blazars, and Gamma-Ray Bursts (GRBs), with the observational capability to study their spectral and spatial morphology enhancing our understanding of their origin and evolution. Looking ahead, the Cherenkov Telescope Array (CTA) represents the next frontier in ground-based gamma-ray astronomy. Operating at very high energies (VHE) between 20 GeV and 300 TeV, CTA's improved sensitivity, angular resolution, and expanded field of view (FoV) promise enhanced imaging of extended sources and performance of large-scale surveys. CTA's Key Science Projects (KSPs) include the Extragalactic (EGAL) survey, a survey of a quarter of the extragalactic sky, and the Galactic Plane Survey (GPS), a survey of the entire Galactic Plane (GP). The KSPs will receive dedicated observation time and careful planning to ensure the optimization of their scientific output. As CTA is currently entering the construction phase, simulations are being extensively employed to predict its response to various signals, playing a vital role in comprehending CTA's response and sensitivity to different signals. The derived predictions are paving the way for estimating the CTA's scientific output, informing the observational strategy, and ensuring its success in maximizing the contribution to HE gamma-ray astronomy. In this thesis, I contribute to assessing the sensitivity of the CTA surveys, particularly the GPS and the EGAL survey, to diverse astrophysical sources and signals. Focusing on the GPS, I delve into understanding the detectability of pulsar halos, which emit multi-TeV gamma rays, the detection of which was recently reported by the HAWC Observatory. The study involves a spatial-spectral likelihood analysis, evaluating sensitivity to simple Gaussian extended sources and physically modeled sources. Employing a template-fitting approach, I analyze CTA's GPS sensitivity to extended sources and explore the prospects for pulsar halo detection and characterization. A preliminary population study addresses the visibility of pulsar halos to CTA's GPS and explores the angular sensitivity to extended sources. The thesis sets the detectability prospects of pulsar halos with CTA and investigates what fraction of the preliminary pulsar halo population CTA will be able to probe. The thesis extends its exploration into the persistent mystery of dark matter (DM), a fundamental puzzle in cosmology. The search for DM signals remains a vigorous pursuit in the physics community, utilizing various astrophysical messengers resulting from DM particle annihilation or decay. I investigate the potential of CTA's GPS to detect dark sub-halos within our galaxy, utilizing a similar approach as in the sensitivity assessment to pulsar halos, applied to recent sub-halo population simulations. Furthermore, the thesis addresses the intricate task of disentangling DM components from astrophysical contributions in the observed gamma-ray sky. In terms of the EGAL survey, employing advanced statistical methods such as the cross-correlation technique, I explore the prospects of using CTA's EGAL survey to correlate the Extragalactic Gamma-ray Background (EGRB) with galaxy catalogs, providing insights into DM properties. While traditional methods rely on likelihood analysis with background subtraction or template fitting, the emergence of supervised machine learning (ML) offers a novel, potentially more effective approach for cataloging the sky. The thesis touches upon the usability of ML in the high and VHE gamma-ray sky. My study focuses on CTA's GPS and utilizes deep-learning-based algorithms in a detection pipeline for the automatic classification of extended sources from gamma-ray data. As CTA stands at the forefront of gamma-ray astronomy as the next-generation observatory, the research presented in this thesis contributes a small step towards answering the open questions about pulsar halos and DM, showcasing the potential breakthroughs that may emerge from CTA's observations. The detailed likelihood analysis performed aims to advance our understanding of these enigmas, from the physical intricacies of pulsar halos to the elusive nature of DM, driven by curiosity about the continuous exploration of the Universe's mysteries.
Ključne besede: high-energy gamma-ray astronomy, astroparticle physics, Cherenkov Telescope Array, pulsar halos, dark matter, dissertations
Objavljeno v RUNG: 06.06.2024; Ogledov: 1407; Prenosov: 17
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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: 2394; Prenosov: 6
Celotno besedilo (27,92 MB)
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