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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, published scientific conference contribution

Abstract: 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.
Keywords: Cherenkov Telescope Array, very-high energy photons, gravitational waves, gravitational wave counterparts
Published in RUNG: 19.09.2023; Views: 1269; Downloads: 6
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Multi-messenger study with the Pierre Auger Observatory
Lili Yang, unpublished invited conference lecture

Abstract: The Pierre Auger Observatory is the largest cosmic ray detector in the world, studying particles with energy above 10^17 eV. Even though Auger is dedicated to charged cosmic rays, it’s also sensitive to ultra-high energy neutral particles, such as photons, neutrinos and neutrons, which are undeflected by magnetic field and pointing back to the source site. More exciting, with the breakthrough observations of gravitational-wave signal, the new era of multi-messenger analysis has come. I will present the recent results and prospects of multi-messenger study with Auger and also the first joint detection of gravitational and electromagnetic radiation from the source, with a focus on the UHE neutrino search.
Keywords: Pierre Auger Observatory, multi-messenger, neutrino, gravitational wave
Published in RUNG: 17.01.2018; Views: 4296; Downloads: 0
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Detection of gravitational waves : Diploma thesis
Gregor Mrak, 2016, undergraduate thesis

Abstract: This report mainly focuses on the first two detections of gravitational waves (GW). At the beginning of the thesis the historical background of GW explorations is discussed by pointing out some arguments and researchers that were essential for the progress. Continuing with the derivation based on the theory of general relativity, in order to express where certain properties derive. In the main part of the report, the subject of interest becomes Laser interferometer gravitational-wave observatory (LIGO), beginning with the problems occurring on the way to detection, describing different noise sources one by one. After pointing out the problems, solutions are discussed, namely the technological advances made to lower the background noise as much as possible. The chapter (4) points out different parts of the detector which are implemented to produce a clearer signal. As only physical noise reduction methods are not enough, digital signal processing algorithms are mentioned as well which are used to analyze the data. Subsequently the required theoretical knowledge is given, so the main part ends with the analysis of actual data taken from LIGO’s public release for both GW150914 and GW151226 events (first and second official detections). In the conclusion of the report a brief descriptions of various detectors besides Ligo are given and some insight of the future detectors that are planned to be built.
Keywords: Gravitational waves, Ligo, Binary black hole merger, gravitational wave interferometry
Published in RUNG: 27.09.2016; Views: 7392; Downloads: 319
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Properties of Null Hypersurfaces
Hovhannes Demirtshyan, 2016, master's thesis

Abstract: The aim of this thesis is to investigate the effects that a lightlike singular hypersurface can have on a congruence of timelike (spacelike) geodesics and to extend the existing theory to the case of null geodesics. The introduction discusses the applications of singular hypersurfaces for the description of physical phenomena, their major classfications and includes a short discussion of the two theoretical approaches that exist to study singular hypersurfaces. The second chapter contains detailed description of these approaches. The theoretical frameworks for both cases of lightlike and timelike (spacelike) hypersurfaces are developed. This chapter also discusses the application of these theories to the case when the hypersurface contains a plane fronted lightlike signal. The final chapter starts with a discussion of the effects that a lightlike singular hypersurface can have on a congruence of timelike (spacelike) geodesics. A new approach to these calculations is presented together with an extension of the theory to the case of a congruence of null geodesics. At the end of the chapter a concrete example and its similarities with the case of timelike geodesics is discussed. In conclusion, the thesis suggests a new mathematical framework for describing a congruence of null geodesics crossing a singular null hypersurface. The results may be applied in experimental physics to detect impulsive signals which are located in singular null hypersurfaces and to this end there is a discussion of the properties and possibilities for a detector of impulsive lightlike signals, which include gravitational waves.
Keywords: singular hypersurface, impulsive signal, gravitational wave, null geodesic, timelike (spacelike) geodesic
Published in RUNG: 16.05.2016; Views: 7897; Downloads: 264
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