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 1 - 9 / 91 1.Detection of gravitational wavesGregor Mrak, 2016, undergraduate thesisAbstract: 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.Found in: ključnih besedahSummary of found: ...Gravitational waves, Ligo, Binary black hole merger, gravitational wave interferometry...Keywords: Gravitational waves, Ligo, Binary black hole merger, gravitational wave interferometryPublished: 27.09.2016; Views: 5790; Downloads: 278 Fulltext (3,27 MB) 2.Search for UHE neutrinos – in coincidence with LIGO GW150914 event – with the Pierre Auger ObservatoryLili Yang, 2016, published scientific conference contribution abstractAbstract: The first gravitational wave transient GW150914 was observed by Advanced LIGO on September 14th, 2015 at 09:50:45 Universal Time. In addition to follow-up electromagnetic observations, the detection of neutrinos will probe deeply and more on the nature of astrophysical sources, especially in the ultra-high energy regime. Neutrinos in the EeV energy range were searched in data collected at the surface detector of the Pierre Auger Observatory within ± 500 s and 1 day after the GW150914 event. No neutrino candidates were found. Based on this non-observation, we derive the first and only one neutrino fluence upper limit at EeV energies for this event at 90% CL, and report constraints on existence of accretion disk around mergers.Found in: ključnih besedahSummary of found: ...gravitational waves, neutrinos, black hole physics...Keywords: gravitational waves, neutrinos, black hole physicsPublished: 06.12.2016; Views: 4032; Downloads: 0 Fulltext (627,39 KB) 3.SIFTING FOR SAPPHIRES: SYSTEMATIC SELECTION OF TIDAL DISRUPTION EVENTS IN iPTFTiara Hung, Suvi Gezari, Tanja Petrushevska, 2018, original scientific articleAbstract: We present results from a systematic selection of tidal disruption events (TDEs) in a wide area (4800 deg2 ) g + R band experiment by the Intermediate Palomar Transient Factory (iPTF) with a rolling cadence of 1 and 3 days. We use photometric selection criteria to down select from a total of 493 nuclear transients detected during the experiment to a sample of 26 blue (g − r < 0 mag) nuclear transients in red host galaxies. Using Swift follow-up UV and X-ray imaging, and ground-based optical spectroscopy, we classify 14 Type Ia supernovae (SNe Ia), 9 highly variable active galactic nuclei (AGNs), 2 confirmed TDEs, and 1 potential core-collapse supernova. From our study, we measure a TDE per galaxy rate of 1.7 +2.85 −1.27 ×10−4 gal−1 yr−1 (90% CL in Poisson statistics) using a galaxy number density estimated from the SDSS luminosity function. We find that it is possible to filter out AGNs by employing a more stringent transient color cut (g − r < −0.2 mag). The UV is an important discriminator for filtering out SN contamination, since in the optical, SNe Ia can appear as blue as TDEs in their early phases. However, the contamination from SN Ia drops significantly with a more stringent spatial offset cut, suggesting higher precision in astrometry is essential for separating TDEs from SNe Ia in the optical. Our most stringent optical photometric selection criteria yields a contamination rate of 4.5:1, allowing for a manageable number of TDE candidates for complete spectroscopic follow-up and real-time classification in the ZTF era.Found in: ključnih besedahSummary of found: ...accretion, accretion disks – black hole physics – galaxies: nuclei – ultraviolet:...Keywords: accretion, accretion disks – black hole physics – galaxies: nuclei – ultraviolet: generalPublished: 02.03.2022; Views: 600; Downloads: 29 Fulltext (1,18 MB) 4.Search for Gamma-Ray Emission from Local Primordial Black Holes with the Fermi Large Area TelescopeGabrijela Zaharijas, 2018, original scientific articleFound in: ključnih besedahSummary of found: ...astroparticle physics, black hole physics, methods: data analysis...Keywords: astroparticle physics, black hole physics, methods: data analysisPublished: 23.08.2018; Views: 2667; Downloads: 0 Fulltext (788,37 KB) 5.On the GeV Emission of the Type I BdHN GRB 130427ALaura Beccera, She Sheng Xue, Yu Wang, Narek Sahakyan, Mile Karlica, Yen-Chen Chen, Simonetta Filippi, Christian Cherubini, Carlo Luciano Bianco, Jorge Armando Rueda, Rahim Moradi, Remo Ruffini, 2019, original scientific articleAbstract: We propose that the inner engine of a type I binary-driven hypernova (BdHN) is composed of Kerr black hole (BH) in a non-stationary state, embedded in a uniform magnetic field B_0 aligned with the BH rotation axis and surrounded by an ionized plasma of extremely low density of 10^−14 g cm−3. Using GRB 130427A as a prototype, we show that this inner engine acts in a sequence of elementary impulses. Electrons accelerate to ultrarelativistic energy near the BH horizon, propagating along the polar axis, θ = 0, where they can reach energies of ~10^18 eV, partially contributing to ultrahigh-energy cosmic rays. When propagating with $\theta \ne 0$ through the magnetic field B_0, they produce GeV and TeV radiation through synchroton emission. The mass of BH, M = 2.31M ⊙, its spin, α = 0.47, and the value of magnetic field B_0 = 3.48 × 10^10 G, are determined self consistently to fulfill the energetic and the transparency requirement. The repetition time of each elementary impulse of energy ${ \mathcal E }\sim {10}^{37}$ erg is ~10^−14 s at the beginning of the process, then slowly increases with time evolution. In principle, this "inner engine" can operate in a gamma-ray burst (GRB) for thousands of years. By scaling the BH mass and the magnetic field, the same inner engine can describe active galactic nuclei.Found in: ključnih besedahSummary of found: ...binary-driven hypernova (BdHN) is composed of Kerr black hole (BH) in a non-stationary state, embedded...Keywords: black hole physics, binaries, gamma-ray burst, neutron stars, supernovae, Astrophysics - High Energy Astrophysical PhenomenaPublished: 20.07.2020; Views: 1789; Downloads: 0 Fulltext (1,09 MB) 6.Follow-up searches for ultra-high energy neutrinos from transient astrophysical sources with the Pierre Auger ObservatoryLukas Zehrer, Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Marta Trini, Samo Stanič, Gašper Kukec Mezek, Andrej Filipčič, Michael Schimp, 2019, published scientific conference contributionFound in: ključnih besedahSummary of found: ...Pierre Auger Observatory, transient astrophysical sources, binary black hole mergers, gravitational wave events, blazar TXS...Keywords: Pierre Auger Observatory, transient astrophysical sources, binary black hole mergers, gravitational wave events, blazar TXS 0506+056, follow-up search for counterpart ultra-high energy neutrinosPublished: 21.12.2020; Views: 1547; Downloads: 51 Fulltext (366,82 KB) 7. 8.Bound debris in stellar TDEsAurora Clerici, A. Gomboc, Taj Jankovič, 2020Found in: ključnih besedahSummary of found: ...tidal disruption, black hole, astronomy, astrophyiscs, hydrodynamics...Keywords: tidal disruption, black hole, astronomy, astrophyiscs, hydrodynamicsPublished: 29.07.2021; Views: 1127; Downloads: 0 Fulltext (5,29 MB) 9.The mass fallback rate of the debris in relativistic stellar tidal disruption eventsTaj Jankovič, 2022, published scientific conference contribution abstractAbstract: Highly energetic stellar tidal disruption events (TDEs) provide a way to study black hole characteristics and their environment. We simulate TDEs in a general relativistic and Newtonian description of a supermassive black hole's gravity. Stars, which are placed on parabolic orbits with different impact parameters, are constructed with the stellar evolution code MESA and therefore have realistic stellar density profiles. We focus our analysis on the mass fallback rate of the debris, which can trace the observed light curve of TDEs. I will present the dependence of the mass fallback rate of the debris on the impact parameter, stellar mass and age as well as the black hole's spin and the choice of the gravity's description.Found in: ključnih besedahSummary of found: ...events (TDEs) provide a way to study black hole characteristics and their environment. We simulate...Keywords: black hole physics, hydrodynamics, relativistic processesPublished: 21.10.2022; Views: 142; Downloads: 2 Fulltext (15,78 MB)This document has many files! More...
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