31. Large-scale cosmic-ray anisotropies measured by the Pierre Auger ObservatoryEsteban Roulet, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, objavljeni znanstveni prispevek na konferenci Opis: An update of the measurements of large-scale anisotropies in the arrival directions of ultra high-energy cosmic rays detected at the Pierre Auger Observatory is presented. The established dipolar anisotropy in right ascension has now reached a significance of 6.8σ when considering all energies above 8 EeV and 5.7 σ when only considering energies between 8 and 16 EeV. The 3D dipole amplitude and direction are reconstructed in four different energy bins above 4 EeV. At energies above 8 EeV it points more than 100∘ away from the Galactic centre, providing evidence that the anisotropy observed is of extragalactic origin. An analysis allowing for both dipolar and quadrupolar anisotropies finds qualitatively similar dipole components and no significant quadrupole components. The results for the angular power spectrum are shown, demonstrating that no other statistically significant multipoles are present. The equatorial dipole components are presented down to 0.03 EeV using a trigger which has been optimized for low energies. We find no significant departures from isotropic expectations below 8 EeV, although below 2 EeV the phases appear to be consistently aligned with the right ascension of the Galactic centre. Finally, model predictions based on source emission scenarios obtained in the combined fit of spectrum and composition data above 0.6 EeV are discussed and compared with observations.
Ključne besede: ultra-high-energy cosmic rays, Pierre Auger Observatory, large scale anisotropies
Objavljeno v RUNG: 24.03.2025; Ogledov: 612; Prenosov: 13
 Celotno besedilo (2,76 MB)
Gradivo ima več datotek! Več... |
32. Astrophysical models to interpret the Pierre Auger Observatory dataJuan Manuel González, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, objavljeni znanstveni prispevek na konferenci Opis: The Pierre Auger Observatory has measured the spectrum of ultra-high-energy cosmic rays with unprecedented precision, as well as the distribution of the depths of the maximum of the shower development in the atmosphere, which provide a reliable estimator of the mass composition. The measurements above 10[sup]17.8 eV can be interpreted assuming two populations of uniformly distributed sources, one with a soft spectrum dominating the flux below few EeV, and another one with a very hard spectrum dominating above that energy. When considering the presence of intense extragalactic magnetic fields between our Galaxy and the closest sources and a high-energy population with low spatial density, a magnetic horizon appears, suppressing the cosmic ray's flux at low-energies, which could explain the very hard spectrum observed at Earth. The distribution of arrival directions, which at energies above 32 EeV shows indications of a correlation with a population of starburst galaxies or the radio galaxy Centaurus A (Cen A), are also important to constrain the sources. It is shown that adding a fractional contribution from these sources of about 20% on top of an homogeneous background leads to an improvement of the model likelihood.
Ključne besede: ultra-high-energy cosmic rays, UHECR energy spectrum, UHECR mass composition, UHECR anisotropies, UHECR propagation, UHECR data interpretation, extragalactic magnetic fields, starburst galaxies, Centaurus A, Pierre Auger Observatory
Objavljeno v RUNG: 24.03.2025; Ogledov: 644; Prenosov: 10
Celotno besedilo (790,55 KB)
Gradivo ima več datotek! Več... |
33. The flux of UHECRs along the supergalactic plane using Pierre Auger Observatory dataArmando Di Matteo, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, objavljeni znanstveni prispevek na konferenci Opis: We use the latest dataset from the surface detector array of the Pierre Auger Observatory, with events detected up to 31 December 2022 and a total exposure of 135,000 km² sr yr, to search for possible excesses in the flux of the most energetic cosmic rays on an intermediate angular scale (top-hat radius 27°, based on our previous results) from regions along the supergalactic plane. We find no indication for any such excesses other than the previously reported one in the Centaurus region, with a post-trial significance around 3σ, which we find extends down to lower energies than previously studied. In particular, the field of view of our dataset overlaps both regions in the northern celestial hemisphere from which excesses of events have been reported by the Telescope Array. With our integral exposures over these regions comparable to the Telescope Array ones, we find no indication of any flux excesses from there, with event counts in good agreement with the expectations from an isotropic distribution.
Ključne besede: ultra-high-energy cosmic rays, Pierre Auger Observatory, anisotropies, Centaurus region
Objavljeno v RUNG: 24.03.2025; Ogledov: 589; Prenosov: 9
Celotno besedilo (5,88 MB)
Gradivo ima več datotek! Več... |
34. Multi-messenger insights into ultra-high-energy cosmic rays from FR0 radio galaxies : emission spectrum, composition, and secondary photons and neutrinosJon Paul Lundquist, Serguei Vorobiov, Lukas Merten, Anita Reimer, Margot Boughelilba, Paolo Da Vela, Fabrizio Tavecchio, Giacomo Bonnoli, Chiara Righi, 2025, objavljeni znanstveni prispevek na konferenci Opis: Despite their low individual luminosity, Fanaroff-Riley Type 0 (FR0) radio galaxies have emerged as potentially significant contributors to the observed flux of ultra-high-energy cosmic rays (UHECRs, E≥10 EeV) due to their substantial prevalence in the local universe. Outnumbering more powerful FR radio galaxies by approximately fivefold within redshifts of z≤0.05, FR0s may contribute a considerable fraction of the total UHECR energy density. The presented comprehensive study employs CRPropa3 simulations to estimate the mass composition and energy spectra of UHECRs emitted by FR0 galaxies. These simulations, which integrate extrapolated FR0 properties and various configurations of intergalactic magnetic fields (both random and structured), are compared to recent data from the Pierre Auger Observatory using three extensive air-shower models. By fitting the simulated spectral indices, rigidity cutoffs, and elemental fractions to Auger’s observed energy spectrum and ⟨lnA⟩ composition, we probe the contribution of FR0 sources to the UHECR flux. Furthermore, we predict the secondary photon and neutrino fluxes resulting from UHECR interactions with cosmic photon backgrounds and compare these results with current upper limits and theoretical models. This multi-messenger approach provides valuable insights into the role of low-luminosity FR0 radio galaxies within the UHECR landscape.
Ključne besede: ultra-high-energy cosmic rays, energy spectrum, mass composition, Fanaroff-Riley type 0
Objavljeno v RUNG: 24.03.2025; Ogledov: 590; Prenosov: 12
Celotno besedilo (5,94 MB)
Gradivo ima več datotek! Več... |
35. Outreach, education, and communication initiatives at the Pierre Auger ObservatoryV. Scherini, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2024, objavljeni znanstveni prispevek na konferenci Opis: The Pierre Auger Collaboration has a long tradition of outreach that engages a wide range of people of all ages worldwide. In Malargüe, Argentina, the heart of the Pierre Auger Observatory, the Visitor Center offers a permanent interactive exhibition. Every November Collaboration meeting, we organize a Science Fair where Argentinian students from across the country can present their works and talk with the scientists at the site, motivating youngsters to pursue a career in Science. We also participate in the local parade, commemorating the foundation of Malargüe. We have developed numerous activities and interactive tools, including a 3-D event display. We have an open data policy and share them according to FAIR principles. Recently, we joined the International Masterclasses within the International Particle Physics Outreach Group, using a framework similar to the ATLAS and CMS Collaborations. In this contribution, we summarize all of our Outreach activities.
Ključne besede: ultra-high-energy cosmic rays, Pierre Auger Observatory, outreach, education, communication, Auger visitor center, Auger science fair, open data policy, FAIR principles, International Particle Physics Outreach Group, International Masterclasses
Objavljeno v RUNG: 17.02.2025; Ogledov: 828; Prenosov: 7
Celotno besedilo (1,90 MB)
Gradivo ima več datotek! Več... |
36. Inference of the Mass Composition of Cosmic Rays with Energies from 10[sup]18.5 to 10[sup]20 eV Using the Pierre Auger Observatory and Deep LearningA. Abdul Halim, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, izvirni znanstveni članek Opis: We present measurements of the atmospheric depth of the shower maximum Xmax,
inferred for the first time on an event-by-event level using the Surface Detector
of the Pierre Auger Observatory. Using deep learning, we were able to extend
measurements of the Xmax distributions up to energies of 100 EeV (10[sup]20 eV),
not yet revealed by current measurements, providing new insights into the mass
composition of cosmic rays at extreme energies.
Gaining a 10-fold increase in statistics compared to the Fluorescence Detector data,
we find evidence that the rate of change of the average Xmax with the logarithm
of energy features three breaks at 6.5 ± 0.6 (stat) ± 1 (sys) EeV,
11 ± 2 (stat) ± 1 (sys) EeV, and 31 ± 5 (stat) ± 3 (sys) EeV, in the vicinity to the three
prominent features (ankle, instep, suppression) of the cosmic-ray flux.
The energy evolution of the mean and standard deviation of the measured Xmax
distributions indicates that the mass composition becomes increasingly heavier
and purer, thus being incompatible with a large fraction of light nuclei between
50 EeV and 100 EeV.
Ključne besede: ultra-high-energy cosmic rays (UHECRs), extensive air showers, Pierre Auger Observatory, UHECR mass composition, depth of the shower maximum, fluorescence detector, surface detector, deep learning
Objavljeno v RUNG: 20.01.2025; Ogledov: 939; Prenosov: 6
Celotno besedilo (586,04 KB)
Gradivo ima več datotek! Več... |
37. Measurement of the depth of maximum of air-shower profiles with energies between ▫$10^{18.5} and 10^{20}$▫ eV using the surface detector of the Pierre Auger Observatory and deep learningA. Abdul Halim, P. Abreu, M. Aglietta, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, izvirni znanstveni članek Opis: We report an investigation of the mass composition of cosmic rays with energies
from 3 to 100 EeV (1 EeV = 10[sup]18 eV) using the distributions of the depth of shower
maximum Xmax. The analysis relies on ∼50,000 events recorded by the surface detector
of the Pierre Auger Observatory and a deep-learning-based reconstruction algorithm.
Above energies of 5 EeV, the dataset offers a 10-fold increase in statistics with respect to
fluorescence measurements at the Observatory. After cross-calibration using
the fluorescence detector, this enables the first measurement of the evolution of the mean
and the standard deviation of the Xmax distributions up to 100 EeV.
Our findings are threefold: (i) The evolution of the mean logarithmic mass toward a heavier
composition with increasing energy can be confirmed and is extended to 100 EeV.
(ii) The evolution of the fluctuations of Xmax toward a heavier and purer composition
with increasing energy can be confirmed with high statistics. We report a rather heavy
composition and small fluctuations in Xmax at the highest energies.
(iii) We find indications for a characteristic structure beyond a constant change
in the mean logarithmic mass, featuring three breaks that are observed in proximity
to the ankle, instep, and suppression features in the energy spectrum.
Ključne besede: ultra-high-energy cosmic rays, UHECRs, extensive air showers, Pierre Auger Observatory, UHECR mass composition, depth of shower maximum, fluorescence detector, surface detector, deep learning
Objavljeno v RUNG: 20.01.2025; Ogledov: 947; Prenosov: 8
Celotno besedilo (2,71 MB)
Gradivo ima več datotek! Več... |
38. Combined fit of spectrum and composition for FR0 radio-galaxy-emitted ultra–high energy cosmic rays with resulting secondary photons and neutrinosJon Paul Lundquist, Serguei Vorobiov, Lukas Merten, Anita Reimer, Margot Boughelilba, Paolo Da Vela, Fabrizio Tavecchio, Giacomo Bonnoli, Chiara Righi, 2025, izvirni znanstveni članek Opis: This study comprehensively investigates the gamma-ray dim population of Fanaroff–Riley
Type 0 (FR0) radio galaxies as potentially significant sources of ultra–high energy cosmic rays
(UHECRs, E > 10[sup]18 eV) detected on Earth. While individual FR0 luminosities are relatively
low compared to the more powerful Fanaroff–Riley Type 1 and Type 2 galaxies, FR0s are
substantially more prevalent in the local universe, outnumbering the more energetic galaxies
by a factor of ∼5 within a redshift of z ≤ 0.05. Employing CRPropa3 simulations, we estimate
the mass composition and energy spectra of UHECRs originating from FR0 galaxies for energies
above 10[sup]18.6 eV. This estimation fits data from the Pierre Auger Observatory (Auger)
using three extensive air shower models; both constant and energy-dependent observed
elemental fractions are considered. The simulation integrates an approximately isotropic
distribution of FR0 galaxies, extrapolated from observed characteristics, with UHECR
propagation in the intergalactic medium, incorporating various plausible configurations of
extragalactic magnetic fields, both random and structured. We then compare the resulting
emission spectral indices, rigidity cutoffs, and elemental fractions with recent Auger results.
In total, 25 combined energy-spectrum and mass-composition fits are considered. Beyond
the cosmic-ray fluxes emitted by FR0 galaxies, this study predicts the secondary photon and
neutrino fluxes from UHECR interactions with intergalactic cosmic photon backgrounds.
The multimessenger approach, encompassing observational data and theoretical models,
helps elucidate the contribution of low-luminosity FR0 radio galaxies to the total cosmic-ray
energy density.
Ključne besede: ultra-high-energy cosmic rays, UHECRs, UHECR energy spectrum, Pierre Auger Observatory, UHECR mass composition, UHECR sources, extragalactic magnetic fields, UHECR propagation, CRPropa tool
Objavljeno v RUNG: 06.01.2025; Ogledov: 929; Prenosov: 10
Celotno besedilo (4,14 MB)
Gradivo ima več datotek! Več... |
39. Large-scale cosmic-ray anisotropies with 19 yr of data from the Pierre Auger ObservatoryA. Abdul Halim, P. Abreu, M. Aglietta, Ingo Allekotte, K. Almeida Cheminant, Jon Paul Lundquist, Shima Ujjani Shivashankara, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2024, izvirni znanstveni članek Opis: We present results of the measurement of large-scale anisotropies in the arrival directions of
ultra–high-energy cosmic rays detected at the Pierre Auger Observatory during 19 yr of operation,
prior to AugerPrime, the upgrade of the observatory. The 3D dipole amplitude and direction are
reconstructed above 4 EeV in four energy bins. Besides the established dipolar anisotropy in right
ascension above 8 EeV, the Fourier amplitude of the 8–16 EeV energy bin is now also above the 5σ
discovery level. No time variation of the dipole moment above 8 EeV is found, setting an upper limit
to the rate of change of such variations of 0.3% per year at the 95% confidence level. Additionally,
the results for the angular power spectrum are shown, demonstrating no other statistically
significant multipoles. The results for the equatorial dipole component down to 0.03 EeV are
presented, using for the first time a data set obtained with a trigger that has been optimized for
lower energies. Finally, model predictions are discussed and compared with observations, based
on two source emission scenarios obtained in the combined fit of spectrum and composition above 0.6 EeV.
Ključne besede: ultra–high-energy cosmic rays, UHECRs, UHECR anisotropies, Pierre Auger Observatory, dipolar anisotropy in right ascension, Fourier amplitude analysis, angular power spectrum, equatorial dipole component, UHECR source emission scenarios
Objavljeno v RUNG: 26.11.2024; Ogledov: 1140; Prenosov: 7
Celotno besedilo (1,16 MB)
Gradivo ima več datotek! Več... |
40. Multi-messenger astrophysics with the Pierre Auger ObservatoryMassimo Mastrodicasa, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, objavljeni znanstveni prispevek na konferenci Opis: The Pierre Auger Observatory is sensitive to ultra-high energy neutral particles, such as photons, neutrinos, and neutrons, and can take part in Multi-Messenger searches in collaboration with other observatories. Photons and neutrinos are searched by exploiting the design of the Pierre Auger Observatory and profiting from the different properties of the induced showers caused by different particles. Diffuse and point source fluxes of photons and neutrinos are searched for. Furthermore, photon and neutrino follow-ups of the gravitational wave events observed by the LIGO/Virgo Collaboration are conducted. The Pierre Auger Observatory is also used to search for neutrons from point-like sources. In contrast to photons and neutrinos, neutrons induce air showers that cannot be distinguished from those produced by protons. For this reason, the search for neutrons from a given source is performed by searching for an excess of air showers from the corresponding direction. All these searches have resulted in stringent upper limits on the corresponding fluxes of the considered particles, allowing, together with the results obtained by other experiments, to shed some light on the most energetic phenomena of our Universe. An overview of the Multi-Messenger activities carried out within the Pierre Auger Collaboration is presented.
Ključne besede: ultra-high-energy cosmic rays, UHE photons, UHE neutrinos, UHE neutrons, Pierre Auger Observatory, multi-messenger astrophysical studies
Objavljeno v RUNG: 04.10.2024; Ogledov: 1231; Prenosov: 6
Celotno besedilo (640,80 KB)
Gradivo ima več datotek! Več... |
