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Monitoring the inter-calibration of the HEAT and Coihueco fluorescence telescopes of the Pierre Auger Observatory with measurements of the brightness of the night sky
Alberto Segreto, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution

Abstract: The High Elevation Auger Telescopes (HEAT) has increased the Field of View (FoV) of the Fluorescence Detector (FD) at the Coihueco site of the Pierre Auger Observatory and allowed the extension of the energy threshold for the measurements of energies and �max of Extensive Air Showers (EAS) down to ≈ 1017.2 eV. By temporarily orienting HEAT in the downward position, it acquires data in the same FoV as the other Coihueco telescopes, thus providing the opportunity to intercalibrate the detectors by multiple observations of the same EAS. To further control systematic uncertainties in �max and energy measurements, in this contribution we present an innovative method that takes advantage of the Night Sky Brightness (NSB) continuously measured with the FD data acquisition system for monitoring a possible evolution in time of the initial HEAT and Coihueco inter-calibration. While the brightness of the night sky evolves unpredictably and is highly dependent on local weather conditions, we expect to obtain consistent measurements from telescopes located at the same site and observing the same direction of the sky. In this work, we describe the method used to compare the NSB measured by the neighboring HEAT and Coihueco telescopes to monitor the stability of their relative calibration over time. This method allows us to study further the systematics in the inter-calibration of the FD telescopes.
Keywords: ultra-high energy cosmic rays, Pierre Auger Observatory, night sky brightness, high elevation Auger telescopes
Published in RUNG: 22.01.2024; Views: 592; Downloads: 5
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Monte Carlo Simulations and Validation of NectarCAM, a Medium Sized Telescope Camera for CTA
Thomas P. Armstrong, Saptashwa Bhattacharyya, Barbara MARČUN, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Gabrijela Zaharijas, Marko Zavrtanik, Danilo Zavrtanik, Miha Živec, 2021, published scientific conference contribution

Abstract: The upcoming Cherenkov Telescope Array (CTA) ground-based gamma-ray observatory will open up our view of the very high energy Universe, o˙ering an improvement in sensitivity of 5-10 times that of previous experiments. NectarCAM is one of the proposed cameras for the Medium-Sized Telescopes (MST) which have been designed to cover the core energy range of CTA, from 100 GeV to 10 TeV. The final camera will be capable of GHz sampling and provide a field of view of 8 degrees with its 265 modules of 7 photomultiplier each (for a total of 1855 pixels). In order to validate the performance of NectarCAM, a partially-equipped prototype has been constructed consisting of only the inner 61-modules. It has so far undergone testing at the integration test-bench facility in CEA Paris-Saclay (France) and on a prototype of the MST structure in Adlershof (Germany). To characterize the performance of the prototype, Monte Carlo simulations were conducted using a detailed model of the 61 module camera in the CORSIKA/sim_telarray framework. This contribution provides an overview of this work including the comparison of trigger and readout performance on test-bench data and trigger and image parameterization performance during on-sky measurements.
Keywords: Cherenkov Telescope Array, ground-based gamma-ray observatory, NectarCAM, Medium-Sized Telescopes
Published in RUNG: 18.09.2023; Views: 808; Downloads: 4
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Tidal Disruption Events seen through the eyes of Vera C. Rubin Observatory
Katja Bučar Bricman, 2021, doctoral dissertation

Abstract: Tidal Disruption Events (TDEs) are rare transients, which are considered to be promising tools in probing supermassive black holes (SMBHs) and their environments in quiescent galaxies, accretion physics, and jet formation mechanisms. The majority of $\approx$ 60 detected TDEs has been discovered with large field of view time-domain surveys in the last two decades. Currently, about 10 TDEs are discovered per year, and we expect this number will increase largely once the Legacy Survey of Space and Time (LSST) at Vera C. Rubin Observatory begins its observations. In this work we demonstrate and explore the capabilities of the LSST to study TDEs. To begin with, we simulate LSST observations of TDEs over $10$ years of survey duration by including realistic SED models from MOSFiT into the simulation framework of the LSST. SEDs are then converted into observed fluxes and light curves are simulated with the LSST observing strategy minion_1016. Simulated observations are used to estimate the number of TDEs the LSST is expected to observe and to assess the possibility of probing the SMBH mass distribution in the Universe with the observed TDE sample. We find that the LSST has a potential of observing ~1000 TDEs per year, the exact number depending on the SMBH mass distribution and the adopted observing strategy. In spite of this large number, we find that probing the SMBH mass distribution with LSST observed TDEs will not be straightforward, especially at the low-mass end. This is largely attributed to the fact that TDEs caused by low-mass black holes ($\le 10^6 M_\odot$) are less luminous and shorter than TDEs by heavier SMBHs ($> 10^6 M_\odot$), and the probability of observationally missing them with LSST is higher. Second, we built a MAF TDE metric for photometric identification of TDEs based on LSST data. We use the metric to evaluate the performance of different proposed survey strategies in identifying TDEs with pre-defined identification requirements. Since TDEs are blue in color for months after peak light, which separates them well from SNe and AGN, we include u-band observations as one of the criteria for a positive identification. We find that the number of identified TDEs strongly depends of the observing strategy and the number of u-band visits to a given field in the sky. Observing strategies with a larger number of u-band observations perform significantly better. For these strategies up to 10% of LSST observed TDEs satisfy the identification requirements.
Keywords: Ground-based ultraviolet, optical and infrared telescopes Astronomical catalogs, atlases, sky surveys, databases, retrieval systems, archives, Black holes, Galactic nuclei (including black holes), circumnuclear matter, and bulges, Infall, accretion, and accretion disks
Published in RUNG: 03.01.2022; Views: 2921; Downloads: 66
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Air Shower Detection by Bistatic Radar
M. Abou Bakr Othman, Jon Paul Lundquist, 2011, published scientific conference contribution

Abstract: Progress in the field of high‐energy cosmic rays is currently limited by the rarity of the most interesting rays striking the Earth. Indeed, the continuation of the field beyond the current generation of observatories may become financially and practically impossible if new ways are not found to achieve remote coverage over large portions of the Earth’s surface. We describe the development of an observatory based on such a new technique: the remote sensing via bistatic radar technology of cosmic ray induced extensive air showers. We build on pilot studies performed by MARIACHI which have demonstrated that air shower radar echoes are detectable, the opportunity afforded by the location of the Northern Hemisphere’s largest “conventional” cosmic ray observatory (The Telescope Array) in radio‐quiet western Utah, and the donation of analog television transmission equipment to this effort by a local television station.
Keywords: UHECR, Remote sensing, Television broadcasting, Cosmic rays, General procedures and instrumentation, Radar telescopes
Published in RUNG: 29.04.2020; Views: 2819; Downloads: 0
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Mass composition of cosmic rays with energies from 10^17.2 eV to 10^20 eV using surface and fluorescence detectors of the Pierre Auger Observatory
Gašper Kukec Mezek, 2018, published scientific conference contribution

Abstract: Ultra-high-energy cosmic rays (UHECRs) are highly energetic particles with EeV energies, exceeding the capabilities of man-made colliders. They hold information on extreme astrophysical processes that create them and the medium they traverse on their way towards Earth. However, their mass composition at such energies is still unclear, because data interpretation depends on our choice of high energy hadronic interaction models. With its hybrid detection method, the Pierre Auger Observatory has the possibility to detect extensive air showers with an array of surface water-Cherenkov stations (SD) and fluorescence telescopes (FD). We present recent mass composition results from the Pierre Auger Collaboration using observational parameters from SD and FD measurements. Using the full dataset of the Pierre Auger Observatory, implications on composition can be made for energies above 10^17.2 eV.
Keywords: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, fluorescence telescopes, water-Cherenkov stations
Published in RUNG: 24.05.2019; Views: 3501; Downloads: 110
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Member of the evaluation committee in charge of awarding with the European mention the doctoral thesis of Dr. Ignacio Vegas Azcárate
Serguei Vorobiov, other performed works

Abstract: I cooperated with the Department of Applied Physics III, Faculty of Physics of the Universidad Complutense of Madrid, Spain, as a member of the evaluation committee in charge of awarding with the European mention the doctoral thesis of Dr. Ignacio Vegas Azcárate, entitled “Nanosecond range pulse generators for quality control and diagnosis of Cherenkov telescope cameras”.
Keywords: very-high energy gamma-ray astronomy, imaging atmospheric Cherenkov telescopes (IACTs), IACT camera quality control and diagnostics, nanosecond range pulse generators
Published in RUNG: 06.03.2018; Views: 4624; Downloads: 0
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High redshift supernova rates measured with a gravitational telescope
Tanja Petrushevska, 2015, published scientific conference contribution abstract

Abstract: Supernovae (SNe) are one the most energetic phenomena in the Universe and have been extensively used for astrophysical and cosmological applications. For example, type Ia SNe as distance indicators tools have revealed the accelerating expansion of the universe, while core-collapse (CC) being directly related to the death of massive stars, they trace the star formation history. One of the challenges of SN research is the measurements of the SN rates, particularly at high-z where not many measurements exist. Possible approach to this problem is to use the magnification power of gravitational telescopes such as galaxy clusters. I will present our ground based near-infrared/optical search for gravitationally magnified supernovae behind the galaxy cluster A1689. Our search resulted in the discovery of five highly magnified candidates at high-z classified as CC SNe. We measure the first volumetric CC SN rates.
Keywords: supernova rates, gravitational telescopes, galaxy clusters
Published in RUNG: 26.01.2018; Views: 3492; Downloads: 0
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