1. 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, original scientific article Abstract: 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.
Keywords: 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
Published in RUNG: 26.11.2024; Views: 409; Downloads: 1
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2. Absolute calibration and investigation of ageing of the AERA radio detectorsRogerio M. De Almeida, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2023, published scientific conference contribution Abstract: The Auger Engineering Radio Array (AERA) is currently the largest facility to measure radio emissions from extensive air showers. Located at the Pierre Auger Observatory in Argentina,
it comprises 153 autonomous radio-detector stations, covering an area of 17 sq. km, and measures radio waves in the frequency range from 30 to 80 MHz. For the correct interpretation of data collected by AERA stations, the detector response has to be carefully calibrated. In the past, this was done by measuring the analogue chain in the laboratory, in addition to simulating and measuring the directional response of the antenna. In this work, we perform an absolute calibration by using the radio emission from the Galaxy. A model of the full radio sky is propagated through the system response, including the antenna, filters and amplifiers, and compared to the average spectra recorded by the stations. The method to determine the calibration constants, as the results, for each antenna will be presented. The behavior of the calibration constants is studied as a function of time from 2014 to 2020. There is no relevant ageing effect over a timescale of 10 years, showing that radio detectors could help to monitor possible ageing effects of other detector systems during long-term operations, stressing their importance in determining an absolute energy scale.
Keywords: Pierre Auger Observatory, ultra-high-energy cosmic rays, extensive air showers, engineering radio array
Published in RUNG: 03.10.2024; Views: 549; Downloads: 1
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3. Long-term calibration and stability of the Auger Engineering Radio Array using the diffuse Galactic radio emissionR. M. de Almeida, Andrej Filipčič, Jonathan Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: The Auger Engineering Radio Array (AERA), part of the Pierre Auger Observatory, is currently the largest facility to measure radio emissions from ultra-high energy extensive air showers. It comprises 153 autonomous radio-detector stations, covering an area of 17 km^2, and measures radio waves in the frequency range from 30 to 80 MHz. An accurate description of the detector response is necessary to interpret the data collected by the stations correctly. Previously, this was achieved by measuring the analog chain in the laboratory and simulating and measuring the directional response of the antenna. In this work, we perform an absolute calibration using the continuously monitored sidereal modulation of the diffuse Galactic radio emission. The calibration is performed by comparing the average spectra recorded by the stations with a model of the full radio sky propagated through the system response, including the antenna, filters, and amplifiers. We describe the method to determine the calibration constants for each antenna and present the corresponding results. Furthermore, the behavior of the calibration constants is studied as a function of time. There is no relevant aging effect over a timescale of a decade, which shows that radio detectors could help monitor possible aging effects of other detector systems during
long-term operations, stressing their importance in determining an absolute energy scale.
Keywords: pierre auger observatory, auger engineering radio array, ultra-high energy cosmic rays, radio detectors
Published in RUNG: 22.01.2024; Views: 1922; Downloads: 38
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4. Cherenkov Telescope Array Science : a multi-wavelength and multi-messenger perspectiveUlisses Barres de Almeida, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, published scientific conference contribution Abstract: The Cherenkov Telescope Array (CTA) will be the major global observatory for
VHE gamma-ray astronomy over the next decade and beyond. It will be an explorer
of the extreme universe, with a broad scientific potential: from understanding the role of relativistic cosmic particles, to the search for dark matter. Covering photon energies from 20 GeV to 300 TeV, and with an angular resolution unique in the field, of about 1 arc min, CTA will improve on all aspects of the performance with respect to current instruments, surveying the high energy sky hundreds of times faster than previous TeV telescopes,
and with a much deeper view. The very large collection area of CTA makes it an important probe of transient phenomena. The first CTA telescope has just been inaugurated in the Canary Islands, Spain, and as more telescopes are added in the coming years, scientific operation will start. It is evident that CTA will have important synergies with many of the
new generation astronomical and astroparticle observatories. In this talk we will review
the CTA science case from the point of view of its synergies with other instruments and
facilities, highlighting the CTA needs in terms of external data, as well as the opportunities and strategies for cooperation to achieve the basic CTA science goals.
Keywords: very-high-energy gamma-ray astronomy, Cherenkov Telescope Array, CTA performances, transient VHE sources, CTA science
Published in RUNG: 04.12.2023; Views: 3159; Downloads: 6
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5. Large-scale and multipolar anisotropies of cosmic rays detected at the Pierre Auger Observatory with energies above 4 EeVR. de Almeida, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, published scientific conference contribution Abstract: More than half a century after the discovery of ultra-high energy cosmic rays (UHECRs), their origin is still an open question. The study of anisotropies in the arrival directions of such particles is an essential ingredient to solve this puzzle. We update our previous analysis of large-scale anisotropies observed by the Pierre Auger Observatory using the latest data collected before the AugerPrime upgrade. We select events with zenith angles up to 80 degrees, implying a sky coverage of 85%, and energies above 4 EeV, for which the surface detector of the Observatory is fully efficient. Dipolar and quadrupolar amplitudes are evaluated through a combined Fourier analysis of the event count rate in right ascension and azimuth. The analysis is performed in three energy bins with boundaries at 4, 8, 16 and 32 EeV and two additional cumulative bins with energies above 8 and 32 EeV. The most significant signal is a dipolar modulation in right ascension for energies above 8 EeV, as previously reported, with statistical significance of 6.6σ. Additionally, we report the measurements of the angular power spectrum for the same energy bins with the same dataset.
Keywords: Pierre Auger Observatory, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, anisotropy, dipole, quadropole, angular power spectrum, inclined showers
Published in RUNG: 03.10.2023; Views: 1702; Downloads: 5
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6. Constraints on the origin of cosmic rays from large scale anisotropy searches in data of the Pierre Auger ObservatoryRogerio M. De Almeida, Andrej Filipčič, Thomas Paul, Samo Stanič, Darko Veberič, Danilo Zavrtanik, Marko Zavrtanik, 2013, published scientific conference contribution Keywords: Observatorij Pierre Auger, kozmični žarki, anizotropija
Published in RUNG: 15.10.2013; Views: 5970; Downloads: 23
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