1. Possible interpretations of the joint observations of UHECR arrival directions using data recorded at the Telescope Array and the Pierre Auger ObservatoryMikhail Kuznetsov, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: Various hints for anisotropies in the distribution of arrival directions of ultra-high-energy cosmic rays (UHECRs) have been reported. Still, our poor knowledge about extragalactic and Galactic
magnetic fields and about the UHECR mass composition makes it non-trivial to interpret such results in terms of possible models of UHECR sources. In this work, we apply the same analyses that have been performed on the Pierre Auger Observatory and the Telescope Array UHECR data to a variety of Monte Carlo simulations generated according to many different combinations of hypotheses about the sources, composition and magnetic deflections of UHECRs. We find that
only some of these models can yield results similar to those obtained with the real data.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, anisotropy, galactic magnetic fields, telescope array, arrival directions
Published in RUNG: 23.01.2024; Views: 1551; Downloads: 7
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2. Update on the searches for anisotropies in UHECR arrival directions with the Pierre Auger Observatory and the Telescope ArrayLorenzo Caccianiga, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: The origin of ultra-high-energy cosmic rays (UHECRs), particles from outer space with energies �≥1 EeV, is still unknown, though the near-isotropy of their arrival direction distribution excludes a dominant Galactic contribution, and interactions with background photons prevent them from travelling cosmologically large distances. This suggests that their sources must be searched for in nearby galaxy groups and clusters. Deflections by intergalactic and Galactic magnetic fields are expected to hinder such searches but not preclude them altogether. So far, the only anisotropy detected with statistical significance ≥ 5� is a modulation in right ascension in the data from the Pierre Auger Observatory at �≥8 EeV interpretable as a 7% dipole moment. Various hints for higher-energy, smaller-scale anisotropies have been reported. UHECR arrival direction data from both the Pierre Auger Observatory and the Telescope Array experiment have been searched for anisotropies by a working group with members from both collaborations; combining the two datasets requires a cross-calibration procedure due to the different systematic uncertainties on energy measurements but allows us to perform analyses that are less model-dependent than what can be done with partial sky coverage. We report a significant dipole pointing away from the Galactic Center and a ∼4.6� anisotropy found when comparing the directions of UHECRs with a catalog of starburst galaxies.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, anisotropy, galactic magnetic fields, telescope array, arrival directions
Published in RUNG: 23.01.2024; Views: 1565; Downloads: 6
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3. Constraining models for the origin of ultra-high-energy cosmic rays with spectrum, composition, and arrival direction data measured at the Pierre Auger ObservatoryTeresa Bister, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: The distribution of cosmic-ray arrival directions shows a better agreement with models in which a fraction of the flux is associated with catalogs of nearby source candidates, such as starburst galaxies, than with isotropy. To investigate this further, we use a novel approach, fitting simultaneously the energy spectrum, distributions of shower maxima, and arrival directions at the highest
energies measured with the Pierre Auger Observatory. The astrophysical model consists of homogeneously distributed background sources as well as an adaptable contribution from nearby source candidates. Propagation effects and a rigidity-dependent magnetic field blurring are taken into account, producing a rising level of anisotropy with the energy. We demonstrate that a model containing a flux fraction of around 20% from the starburst galaxy catalog at 40 EeV, with a hard, nitrogen-dominated injection spectrum, provides a good description of the data. By investigating a scenario with Cen A as a single source in combination with the homogeneous background, we
show that this region of the sky provides the dominant part to the observed anisotropy signal. Models based on jetted active galactic nuclei whose cosmic-ray flux scales with the gamma-ray emission are disfavored. The modeled energy evolution of the arrival directions, the spectra of individual sources, as well as the statistical significance of the results, including the influence of experimental systematic effects, will be discussed in this contribution.
Keywords: anisotropies, Pierre Auger Observatory, ultra-high energy cosmic-rays, arrival directions
Published in RUNG: 22.01.2024; Views: 1550; Downloads: 5
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4. An update on the arrival direction studies made with data from the Pierre Auger ObservatoryGeraldina Golup, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: The search for anisotropies in the arrival directions of ultra-high-energy cosmic rays plays a key role in the efforts to understand their origin. The observed first-harmonic modulation in right ascension above 8 EeV, detected by the Pierre Auger Observatory with a current significance of 6.9�, suggests an extragalactic origin above this energy. Furthermore, there are indications, at the ∼4� significance level, of anisotropies at intermediate angular scales, which are obtained when comparing the arrival directions against the distribution of potential sources from astrophysical catalogs, in particular that of nearby starburst galaxies, and around the Centaurus region. In this contribution, we present the status of the different searches for anisotropies at small, intermediate
and large angular scales. We use the latest available data set, with 19 years of operation that has yielded 135,000 km^2 yr sr of accumulated exposure, covering the sky at declinations from −90◦ to
45◦. At small and intermediate scales, we report updates of the all-sky blind search for localized excesses, the study around the Centaurus region, and the likelihood analysis with catalogs of
candidate sources. We have also studied the regions of the sky from which the Telescope Array Collaboration has reported hints of excesses in their data and we find no significant effects in
the same directions with a data set of comparable size. At large angular scales, the dipolar and quadrupolar amplitudes in energy bins are updated. We discuss the prospects of these searches,
both in regards to increases in statistics and in relation to the future inclusion of event-by-event mass estimators in these analyses through the upgrade of the Observatory, AugerPrime.
Keywords: anisotropies, Pierre Auger Observatory, ultra-high energy cosmic-rays, arrival directions
Published in RUNG: 22.01.2024; Views: 1474; Downloads: 7
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5. Telescope Array Surface Detector Energy and Arrival Direction Estimation Using Deep LearningO. Kalashev, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: A novel ultra-high-energy cosmic rays energy and arrival direction reconstruction method for Telescope Array surface detector is presented. The analysis is based on a deep convolutional neural network using detector signal time series as the input and the network is trained on a large Monte-Carlo dataset. This method is compared in terms of statistical and systematic energy and arrival direction determination errors with the standard Telescope Array surface detector event reconstruction procedure.
Keywords: Telescope Array, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, energy, arrival directions, reconstruction, machine learning, neural network
Published in RUNG: 04.10.2023; Views: 1593; Downloads: 8
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6. Search for Correlations of High-energy Neutrinos and Ultra-high Energy Cosmic RaysA.M. Barbano, Andrej Filipčič, Gašper Kukec Mezek, Jon Paul Lundquist, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, published scientific conference contribution Keywords: ultra-high energy cosmic rays (UHECR), high-energy neutrinos, arrival directions, correlation search, IceCube neutrino
observatory, Pierre Auger Observatory, Telescope Array, ANTARES neutrino observatory
Published in RUNG: 22.12.2020; Views: 3392; Downloads: 91
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7. Search for magnetically-induced signatures in the arrival directions of ultra-high energy cosmic rays measured by the Pierre Auger ObservatoryMarcus Wirtz, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, published scientific conference contribution Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays (UHECR), UHECR arrival directions, Galactic magnetic field (GMF), UHECR deflection patterns in GMF, search for magnetically-induced signatures in UHECR arrival directions
Published in RUNG: 21.12.2020; Views: 2945; Downloads: 75
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8. Large-scale anisotropies above 0.03 EeV measured by the Pierre Auger ObservatoryEsteban Roulet, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, published scientific conference contribution Keywords: ultra-high energy cosmic rays (UHECRs), Pierre Auger Observatory, UHECR arrival directions, large-scale anisotropies
Published in RUNG: 24.07.2020; Views: 3578; Downloads: 78
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9. Search for magnetically-induced signatures in the arrival directions of ultra-high-energy cosmic rays measured at the Pierre Auger ObservatoryA. Aab, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Marta Trini, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2020, original scientific article Keywords: ultra-high-energy cosmic rays (UHECR), Pierre Auger Observatory, UHECR arrival directions, galactic magnetic field, UHECR event multiplets
Published in RUNG: 19.06.2020; Views: 3362; Downloads: 0
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10. Arrival directions of the highest-energy cosmic rays detected by the Pierre Auger ObservatoryUgo Giaccari, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, 2017, published scientific conference contribution Keywords: Arrival directions, highest-energy cosmic rays, Pierre Auger Observatory
Published in RUNG: 16.02.2018; Views: 3907; Downloads: 170
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