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1.
A Search for Ultra-high-energy Neutrinos from TXS 0506+056 Using the Pierre Auger Observatory
Marko Zavrtanik, Lukas Zehrer, Danilo Zavrtanik, Serguei Vorobiov, Marta Trini, Samo Stanič, Gašper Kukec Mezek, Andrej Filipčič, A. Aab, 2020, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...TXS 0506+056, the Pierre Auger Observatory, high-energy astrophysics, neutrino astronomy, blazars, transient sources, active galaxies...
Ključne besede: ultra-high energy neutrinos, blazar TXS 0506+056, the Pierre Auger Observatory, high-energy astrophysics, neutrino astronomy, blazars, transient sources, active galaxies
Objavljeno: 20.10.2020; Ogledov: 917; Prenosov: 0
.pdf Polno besedilo (696,03 KB)

2.
The spectrum and morphology of the Fermi bubbles
Gabrijela Zaharijas, M. Ackermann, Adrien Albert, W. B. Atwood, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, R. Bellazzini, Elisabetta Bissaldi, R. D. Blandford, 2014, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...high energy astrophysics, gamma-rays, diffuse background, ...
Ključne besede: high energy astrophysics, gamma-rays, diffuse background
Objavljeno: 09.05.2017; Ogledov: 2193; Prenosov: 15
URL Polno besedilo (0,00 KB)

3.
SUMMER SCHOOL AT FYSIKUM
Tanja Petrushevska, druga izvedena dela

Opis: This summer, for two weeks, 120 high school students (out of 750 applicants) had the opportunity to taste how research is done at Stockholm University. The students worked in small groups under the supervision of doctoral students in chemistry, physics, biology and geology. At the Physics department, the two PhD students Tanja Petrushevska and Seméli Papadogiannakis offered a project that involved supernovae and their host galaxies.
Najdeno v: ključnih besedah
Ključne besede: summer school for high school students in astrophysics
Objavljeno: 06.02.2018; Ogledov: 1532; Prenosov: 0
.pdf Polno besedilo (247,35 KB)

4.
5.
Evidence for Declination Dependence of Ultrahigh Energy Cosmic Ray Spectrum in the Northern Hemisphere
J. P. Lundquist, R.U. Abbasi, 2018, drugi članki ali sestavki

Opis: The energy of the ultrahigh energy spectral cutoff was measured, integrating over the northern hemisphere sky, by the Telescope Array (TA) collaboration, to be 10^19.78±0.06 eV, in agreement with the High Resolution Fly's Eye (HiRes) experiment, whereas the Pierre Auger experiment, integrating over the southern hemisphere sky, measured the cutoff to be at 10^19.62±0.02 eV. An 11% energy scale difference between the TA and Auger does not account for this difference. However, in comparing the spectra of the Telescope Array and Pierre Auger experiments in the band of declination common to both experiments ( −15.7∘<δ<24.8∘ ) we have found agreement in the energy of the spectral cutoff. While the Auger result is essentially unchanged, the TA cutoff energy has changed to 10^19.59±0.06 eV. In this paper we argue that this is an astrophysical effect.
Najdeno v: ključnih besedah
Povzetek najdenega: ... Astrophysics, High Energy Astrophysical Phenomena, UHECR, Cosmic Rays,...
Ključne besede: Astrophysics, High Energy Astrophysical Phenomena, UHECR, Cosmic Rays, Anisotropy, Energy Spectrum
Objavljeno: 27.04.2020; Ogledov: 1129; Prenosov: 41
.pdf Polno besedilo (687,87 KB)

6.
Magnetic Fields and Afterglows of BdHNe: Inferences from GRB 130427A, GRB 160509A, GRB 160625B, GRB 180728A, and GRB 190114C
Jorge Armando Rueda, Remo Ruffini, Mile Karlica, Rahim Moradi, Yu Wang, 2020, izvirni znanstveni članek

Opis: GRB 190114C is the first binary-driven hypernova (BdHN) fully observed from initial supernova (SN) appearance to the final emergence of the optical SN signal. It offers an unprecedented testing ground for the BdHN theory, which is here determined and further extended to additional gamma-ray bursts (GRBs). BdHNe comprise two subclasses of long GRBs, with progenitors a binary system composed of a carbon–oxygen star (COcore) and a neutron star (NS) companion. The COcore explodes as an SN, leaving at its center a newborn NS (νNS). The SN ejecta hypercritically accretes on both the νNS and the NS companion. BdHNe I are very tight binaries, where the accretion leads the companion NS to gravitationally collapse into a black hole (BH). In BdHN II, the accretion rate onto the NS is lower, so there is no BH formation. We observe the same afterglow structure for GRB 190114C and other selected examples of BdHNe I (GRB 130427A, GRB 160509A, GRB 160625B) and for BdHN II (GRB 180728A). In all cases, the afterglows are explained via the synchrotron emission powered by the νNS, and their magnetic field structures and their spin are determined. For BdHNe I, we discuss the properties of the magnetic field embedding the newborn BH, which was inherited from the collapsed NS and amplified during the gravitational collapse process, and surrounded by the SN ejecta.
Najdeno v: ključnih besedah
Povzetek najdenega: ... Astrophysics - High Energy Astrophysical Phenomena, Astrophysics -...
Ključne besede: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, General Relativity and Quantum Cosmology
Objavljeno: 20.07.2020; Ogledov: 850; Prenosov: 0
.pdf Polno besedilo (1,37 MB)

7.
On the GeV Emission of the Type I BdHN GRB 130427A
Laura 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, izvirni znanstveni članek

Opis: 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.
Najdeno v: ključnih besedah
Povzetek najdenega: ...energies of ~10^18 eV, partially contributing to ultra high-energy cosmic rays. When propagating with $\theta \ne... ...physics, binaries, gamma-ray burst, neutron stars, supernovae, Astrophysics - High Energy Astrophysical Phenomena...
Ključne besede: black hole physics, binaries, gamma-ray burst, neutron stars, supernovae, Astrophysics - High Energy Astrophysical Phenomena
Objavljeno: 20.07.2020; Ogledov: 942; Prenosov: 0
.pdf Polno besedilo (1,09 MB)

8.
Electromagnetic emission of white dwarf binary mergers
Jorge Armando Rueda, Remo Ruffini, Yu Wang, Carlo Luciano Bianco, J.M. Blanco-Iglesias, Mile Karlica, P. Lorén-Aguilar, Rahim Moradi, Narek Sahakyan, 2019, izvirni znanstveni članek

Opis: It has been recently proposed that the ejected matter from white dwarf (WD) binary mergers can produce transient, optical and infrared emission similar to the "kilonovae" of neutron star (NS) binary mergers. To confirm this we calculate the electromagnetic emission from WD-WD mergers and compare with kilonova observations. We simulate WD-WD mergers leading to a massive, fast rotating, highly magnetized WD with an adapted version of the smoothed-particle-hydrodynamics (SPH) code Phantom. We thus obtain initial conditions for the ejecta such as escape velocity, mass and initial position and distribution. The subsequent thermal and dynamical evolution of the ejecta is obtained by integrating the energy-conservation equation accounting for expansion cooling and a heating source given by the fallback accretion onto the newly-formed WD and its magneto-dipole radiation. We show that magnetospheric processes in the merger can lead to a prompt, short gamma-ray emission of up to ≈ 1046 erg in a timescale of 0.1-1 s. The bulk of the ejecta initially expands non-relativistically with velocity 0.01 c and then it accelerates to 0.1 c due to the injection of fallback accretion energy. The ejecta become transparent at optical wavelengths around ~ 7 days post-merger with a luminosity 1041-1042 erg s-1. The X-ray emission from the fallback accretion becomes visible around ~ 150-200 day post-merger with a luminosity of 1039 erg s-1. We also predict the post-merger time at which the central WD should appear as a pulsar depending on the value of the magnetic field and rotation period.
Najdeno v: ključnih besedah
Povzetek najdenega: ... Astrophysics - High Energy Astrophysical Phenomena...
Ključne besede: Astrophysics - High Energy Astrophysical Phenomena
Objavljeno: 20.07.2020; Ogledov: 868; Prenosov: 0
.pdf Polno besedilo (8,22 MB)

9.
Evidence for a supergalactic structure of magnetic deflection multiplets of ultra-high-energy cosmic rays
R. U. Abbasi, T. Abu-Zayyad, Mitsuhiro Abe, M. Allen, R. Azuma, E. Barcikowski, J. W. Belz, D. R. Bergman, S. A. Blake, Jon Paul Lundquist, 2020, izvirni znanstveni članek

Opis: Evidence for a large-scale supergalactic cosmic-ray multiplet (arrival directions correlated with energy) structure is reported for ultra-high-energy cosmic-ray (UHECR) energies above 1019 eV using 7 years of data from the Telescope Array (TA) surface detector and updated to 10 years. Previous energy–position correlation studies have made assumptions regarding magnetic field shapes and strength, and UHECR composition. Here the assumption tested is that, because the supergalactic plane is a fit to the average matter density of the local large-scale structure, UHECR sources and intervening extragalactic magnetic fields are correlated with this plane. This supergalactic deflection hypothesis is tested by the entire field-of-view (FOV) behavior of the strength of intermediate-scale energy–angle correlations. These multiplets are measured in spherical cap section bins (wedges) of the FOV to account for coherent and random magnetic fields. The structure found is consistent with supergalactic deflection, the previously published energy spectrum anisotropy results of the TA (the Hotspot and Coldspot), and toy-model simulations of a supergalactic magnetic sheet. The seven year data posttrial significance of this supergalactic structure of multiplets appearing by chance, on an isotropic sky, is found by Monte Carlo simulation to be 4.2σ. The 10 years of data posttrial significance is 4.1σ. Furthermore, the starburst galaxy M82 is shown to be a possible source of the TA Hotspot, and an estimate of the supergalactic magnetic field using UHECR measurements is presented.
Najdeno v: ključnih besedah
Povzetek najdenega: ...ultra-high-energy cosmic radiation, cosmic rays, high energy astrophysics, astrophysical magnetism, cosmic ray astronomy, cosmic ray...
Ključne besede: extragalactic magnetic fields, ultra-high-energy cosmic radiation, cosmic rays, high energy astrophysics, astrophysical magnetism, cosmic ray astronomy, cosmic ray sources
Objavljeno: 05.02.2021; Ogledov: 654; Prenosov: 47
URL Polno besedilo (0,00 KB)
Gradivo ima več datotek! Več...

10.
Two-integral distribution functions in axisymmetric galaxies: Implications for dark matter searches
Piero Ullio, Mihael Petač, 2019, izvirni znanstveni članek

Opis: We address the problem of reconstructing the phase-space distribution function for an extended collisionless system, with known density profile and in equilibrium within an axisymmetric gravitational potential. Assuming that it depends on only two integrals of motion, namely the energy and the component of the angular momentum along the axis of symmetry Lz , there is a one-to-one correspondence between the density profile and the component of the distribution function that is even in Lz, as well as between the weighted azimuthal velocity profile and the odd component. This inversion procedure was originally proposed by Lynden-Bell and later refined in its numerical implementation by Hunter and Qian; after overcoming a technical difficulty, we apply it here for the first time in presence of a strongly flattened component, as a novel approach of extracting the phase-space distribution function for dark matter particles in the halo of spiral galaxies. We compare results obtained for realistic axisymmetric models to those in the spherical symmetric limit as assumed in previous analyses, showing the rather severe shortcomings in the latter. We then apply the scheme to the Milky Way and discuss the implications for the direct dark matter searches. In particular, we reinterpret the null results of the Xenon1T experiment for spin-(in)dependent interactions and make predictions for the annual modulation of the signal for a set of axisymmetric models, including a self-consistently defined corotating halo.
Najdeno v: ključnih besedah
Povzetek najdenega: ...dark matter, astrophysics of galaxies, high energy physics, phenomenology...
Ključne besede: dark matter, astrophysics of galaxies, high energy physics, phenomenology
Objavljeno: 01.10.2021; Ogledov: 152; Prenosov: 0
.pdf Polno besedilo (1,22 MB)

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