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1.
Arrival directions of the highest-energy cosmic rays detected with the Pierre Auger Observatory
Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Darko Veberič, Marta Trini, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, Julien Aublin, 2015, objavljeni znanstveni prispevek na konferenci

Opis: We present the results of a search for small to intermediate scale anisotropies in the distribution of arrival directions of ultra-high energy cosmic rays recorded at the Pierre Auger Observatory. The data set, gathered in ten years of operation, includes arrival directions with zenith angles up to 80◦, and is about three times larger than that used in earlier studies. We update the test based on correlations with active galactic nuclei (AGNs) from the Véron-Cetty and Véron catalog, which does not yield a significant indication of anisotropy with the present data set. We perform a blind search for localized excess fluxes and for self-clustering of arrival directions at angular scales up to 30◦ and for different energy thresholds between 40 EeV and 80 EeV. We also examine the correlation of arrival directions with relatively nearby galaxies in the 2MRS catalog, AGNs detected by Swift-BAT, and a sample of radio galaxies with jets and with the Centaurus A galaxy. None of the searches shows a statistically significant evidence of anisotropy. The two largest departures from isotropy that were found have a post-trial probability ≈ 1.4%. One is for cosmic rays with energy above 58 EeV that arrive within 15◦ of the direction toward Centaurus A. The other is for arrival directions within 18◦ of Swift-BAT AGNs closer than 130 Mpc and brighter than 10[sup]44 erg/s, with the same energy threshold.
Najdeno v: ključnih besedah
Povzetek najdenega: ...does not yield a significant indication of anisotropy with the present data set. We perform...
Ključne besede: ultra-high energy cosmic rays anisotropy studies active galactic nuclei Pierre Auger Observatory
Objavljeno: 02.03.2016; Ogledov: 2006; Prenosov: 144
.pdf Polno besedilo (1,32 MB)

2.
Indications of anisotropy at large angular scales in the arrival directions of cosmic rays detected at the Pierre Auger Observatory
Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Darko Veberič, Marta Trini, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, Imen Al Samarai, 2015, objavljeni znanstveni prispevek na konferenci

Opis: The large-scale distribution of arrival directions of high-energy cosmic rays carries major clues to understanding their origin. The Pierre Auger Collaboration have implemented different analyses to search for dipolar and quadrupolar anisotropies in different energy ranges spanning four orders of magnitude. A common phase ≈270◦ of the first harmonic modulation in right-ascension was found in adjacent energy intervals below 1 EeV, and another common phase ≈100◦ above 4 EeV. A constancy of phase measurements in ordered energy intervals originating from a genuine anisotropy is expected to appear with a smaller number of events than those needed to achieve significant amplitudes. This led us to design a prescribed test aimed at establishing whether this consistency in phases is real at 99% CL. The test required a total independent exposure of 21,000 km2 sr yr. We report on the status of this prescription. We also report the results of the search for a dipole anisotropy for cosmic rays with energies above 4 EeV using events with zenith angles between 60◦ and 80◦. Compared to previous analyses of events with zenith angles smaller than 60◦, this extension increases the size of the data set by 30%, and enlarges the fraction of exposed sky from 71% to 85%. The largest departure from isotropy is found in the energy range above 8 EeV, with an amplitude for the first harmonic in right ascension r1 = (4.4 ± 1.0) × 10[sup]−2, that has a chance probability P(≥ r1) = 6.4×10[sup]−5, reinforcing the hint previously reported with vertical events alone.
Najdeno v: ključnih besedah
Ključne besede: high-energy cosmic rays large-scale distribution anisotropy studies Pierre Auger Observatory
Objavljeno: 02.03.2016; Ogledov: 1911; Prenosov: 146
.pdf Polno besedilo (862,90 KB)

3.
Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data
Gabrijela Zaharijas, 2017, izvirni znanstveni članek

Najdeno v: ključnih besedah
Ključne besede: high energy cosmic rays, anisotropy
Objavljeno: 07.03.2017; Ogledov: 1370; Prenosov: 1
.pdf Polno besedilo (270,43 KB)

4.
Dipolar anisotropy of cosmic rays above 8 EeV
Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Marta Trini, Samo Stanič, Ahmed Saleh, Gašper Kukec Mezek, Andrej Filipčič, Oscar Taborda, 2017, objavljeni znanstveni prispevek na konferenci

Najdeno v: ključnih besedah
Ključne besede: Pierre Auger Observatory, dipolar anisotropy, cosmic rays
Objavljeno: 16.02.2018; Ogledov: 678; Prenosov: 71
.pdf Polno besedilo (411,21 KB)

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Magnetic anisotropy of strontium ferrite nanoparticles
F. Albertini, C. Sangregorio, Blaž Belec, A. Quesada, T. Schliesch, M. Suara-Muzquiz, Petra Jenuš, M. Albino, M. Petrecca, M. Cabassi, D. Mishra, Cesar de Julian Fernandez, 2019, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: ključnih besedah
Ključne besede: hexaferrite, nanoparticles, magnetic anisotropy, SPD
Objavljeno: 04.06.2019; Ogledov: 636; Prenosov: 0
.pdf Polno besedilo (36,89 MB)

8.
Eenergy Anisotropies of Proton-like Ultra-High Energy Cosmic Rays
J. P. Lundquist, doktorska disertacija

Opis: Evidence of a number of interrelated energy dependent intermediate-scale anisotropies have been found in the arrival directions of proton-like ultra-high energy cosmic rays (UHECR) using 7 years of Telescope Array (TA) data. These are found using analysis techniques that have been developed for this dissertation. Using surface detector (SD) data the reported TA “Hotspot” excess, E≥10^19.75 eV, is found to correspond to a deficit, or “Coldspot,” of events for 10^19.1≤E<10^19.75 eV at 142◦R.A., 40◦ Dec. The global post-trial significance of this Hot/Coldspot event density asymmetry is found to be 5.1σ (p = 1.56 × 10−7). This Hot/Coldspot feature is the combination, at the same location, of an energy spectrum anisotropy with a 3.74σ significance for energies E≥10^19.2 eV and an energy-distance correlation with a 3.34σ significance for energies E≥1019.3 eV. The UHECR Hotspot alone is analyzed using a new kernel density estimation (KDE) anisotropy method and found to have a 3.65σ significance (E≥1019.75 eV). These features suggest energy dependent magnetic deflection of UHECR. The composition of UHECR primary particles is also studied using a new “Quality Factor Analysis” pattern recognition event selection for fluorescence detectors (FD). This minimizes the energy dependence of the resolution of extensive air shower (EAS) Xmax depth. Also, a new statistical method making use of all higher moments than the mean shower depth distribution is developed – as there is large disagreement in between all EAS simulation models. There is also an uncertainty, just as large, for any particular model, given uncertainties in particle interaction parameters extrapolated to much higher energies from Large Hadron Collider (LHC) data. The TA hybrid FD/SD data is found to be statistically compatible with a pure proton composition, though not incompatible with a light mixed composition, for all models of EAS above E≥10^18.4 eV. There is also no statistically significant evidence of the composition getting heavier at the highest energies. The combined information of a proton-like light composition, and anisotropy evidence suggestive of energy dependent magnetic deflection of UHECR, should be useful for informing future source searches and models of intergalactic propagation through magnetic fields.
Najdeno v: ključnih besedah
Povzetek najdenega: ...the same location, of an energy spectrum anisotropy with a 3.74σ significance for energies E≥10^19.2...
Ključne besede: cosmic rays, UHECR, composition, anisotropy
Objavljeno: 24.04.2020; Ogledov: 188; Prenosov: 0
.pdf Polno besedilo (10,26 MB)

9.
Evidence of Intermediate-scale Energy Spectrum Anisotropy of Cosmic Rays E ≥ 10^19.2 eV with the Telescope Array Surface Detector
J. P. Lundquist, R.U. Abbasi, 2018, izvirni znanstveni članek

Opis: Evidence for an intermediate-scale energy spectrum anisotropy has been found in the arrival directions of ultra-high energy cosmic rays for energies greater than 10^19.2 eV in the northern hemisphere using 7 years of Telescope Array surface detector data. A relative energy distribution test is done comparing events inside oversampled spherical caps of equal exposure, to those outside, using the Poisson likelihood ratio. The center of maximum significance is at 9h16m, 45°, and has a deficit of events with energies 10^19.2 ≤ E < 10^19.75 eV and an excess for E ≥ 10^19.75 eV. The post-trial probability of this energy anisotropy, appearing by chance anywhere on an isotropic sky, is found by Monte Carlo simulation to be 9 × 10−5 (3.74σ global).
Najdeno v: ključnih besedah
Ključne besede: astroparticle physics, cosmic rays, anisotropy, large-scale structure of universe
Objavljeno: 24.04.2020; Ogledov: 195; Prenosov: 7
.pdf Polno besedilo (1,43 MB)

10.
Full-sky searches for anisotropies in UHECR arrival directions with the Pierre Auger Observatory and the Telescope Array
J. P. Lundquist, A. di Matteo, 2020, objavljeni znanstveni prispevek na konferenci

Najdeno v: ključnih besedah
Ključne besede: UHECR, Cosmic Rays, Anisotropy
Objavljeno: 27.04.2020; Ogledov: 144; Prenosov: 0
.pdf Polno besedilo (6,28 MB)

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