1. Probing extreme environments with the Cherenkov Telescope ArrayC. Boisson, Anthony M. Brown, A. Burtovoi, M. Cerruti, M. Chernyakova, T. Hassan, J.-P. Lenain, Marina Manganaro, Serguei Vorobiov, Danilo Zavrtanik, 2021, other component parts Abstract: The physics of the non-thermal Universe provides information on the acceleration mechanisms in extreme environments, such as black holes and relativistic jets, neutron stars, supernovae or clusters of galaxies. In the presence of magnetic fields, particles can be accelerated towards relativistic energies. As a consequence, radiation along the entire electromagnetic spectrum can be observed, and extreme environments are also the most likely sources of multi-messenger emission. The most energetic part of the electromagnetic spectrum corresponds to the very-high-energy (VHE, E>100 GeV) gamma-ray regime, which can be extensively studied with ground based Imaging Atmospheric Cherenkov Telescopes (IACTs). The results obtained by the current generation of IACTs, such as H.E.S.S., MAGIC, and VERITAS, demonstrate the crucial importance of the VHE band in understanding the non-thermal emission of extreme environments in our Universe. In some objects, the energy output in gamma rays can even outshine the rest of the broadband spectrum. The Cherenkov Telescope Array (CTA) is the next generation of IACTs, which, with cutting edge technology and a strategic configuration of ~100 telescopes distributed in two observing sites, in the northern and southern hemispheres, will reach better sensitivity, angular and energy resolution, and broader energy coverage than currently operational IACTs. With CTA we can probe the most extreme environments and considerably boost our knowledge of the non-thermal Universe.
Keywords: black holes, relativistic jets, neutron stars, supernovae, clusters of galaxies, particle acceleration mechanisms, very-high-energy gamma rays, Cherenkov Telescope Array Observatory
Published in RUNG: 10.01.2025; Views: 468; Downloads: 4
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2. Submicron aerosol pollution in Greater Cairo (Egypt) : a new type of urban haze?Aliki Christodoulou, Spiros Bezantakos, Efstratios Bourtsoukidis, Iasonas Stavroulas, Michael Pikridas, Konstantina Oikonomou, Minas Iakovides, Salwa K. Hassan, Mohamed Boraiy, Mostafa El-Nazer, 2024, original scientific article Keywords: megacity, submicron aerosols, urban haze, Greater Cairo, hygroscopic aerosols, ammonium chloride
Published in RUNG: 10.05.2024; Views: 1618; Downloads: 6
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3. Wavelength-resolved reverberation mapping of quasar CTS C30.10: Dissecting Mg II and Fe II emission regionsRaj Prince, Michal Zajaček, Bożena Czerny, Piotr Trzcionkowski, Mateusz Bronikowski, Catalina Sobrino Figaredo, Swayamtrupta Panda, Mary Loli Martinez-Aldama, Krzysztof Hryniewicz, Vikram Kumar Jaiswal, Marzena Śniegowska, Mohammad-Hassan Naddaf, Maciej Bilicki, Martin Haas, Marek Jacek Sarna, Vladimir Karas, Aleksandra Olejak, Robert Przyłuski, Mateusz Rałowski, Andrzej Udalski, Ramotholo R. Sefako, Anja Genade, Hannah L. Worters, 2022, original scientific article Abstract: Context. We present the results of the reverberation monitoring of the Mg II broad line and Fe II pseudocontinuum for the luminous quasar CTS C30.10 (z = 0.90052) with the Southern African Large Telescope in 2012–2021.
Aims. We aimed at disentangling the Mg II and UV Fe II variability and the first measurement of UV Fe II time delay for a distant quasar.
Methods. We used several methods for the time-delay measurements and determined the Fe II and Mg II time delays. We also performed a wavelength-resolved time delay study for a combination of Mg II and Fe II in the 2700–2900 Å rest-frame wavelength range.
Results. We obtain a time delay for Mg II of 275.5−19.5+12.4 days in the rest frame, and we have two possible solutions of 270.0−25.3+13.8 days and 180.3−30.0+26.6 in the rest frame for Fe II. Combining this result with the old measurement of Fe II UV time delay for NGC 5548, we discuss for first time the radius-luminosity relation for UV Fe II with the slope consistent with 0.5 within the uncertainties.
Conclusions. Because the Fe II time delay has a shorter time-delay component but the lines are narrower than Mg II, we propose that the line-delay measurement is biased toward the part of the broad line region (BLR) facing the observer. The bulk of the Fe II emission may arise from the more distant BLR region, however, the region that is shielded from the observer.
Keywords: accretion, accretion disks / quasars: emission lines / quasars: individual: CTS C30.10 / techniques: spectroscopic / techniques: photometric
Published in RUNG: 13.11.2023; Views: 2411; Downloads: 5
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4. Performance of a proposed event-type based analysis for the Cherenkov Telescope ArrayTarek Hassan, 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 Cherenkov Telescope Array (CTA) will be the next-generation observatory in the field of very-high-energy (20 GeV to 300 TeV) gamma-ray astroparticle physics. Classically, data analysis in the field maximizes sensitivity by applying quality cuts on the data acquired. These cuts, optimized using Monte Carlo simulations, select higher quality events from the initial dataset. Subsequent steps of the analysis typically use the surviving events to calculate one set of instrument response functions (IRFs). An alternative approach is the use of event types, as implemented in experiments such as the Fermi-LAT. In this approach, events are divided into sub-samples based on their reconstruction quality, and a set of IRFs is calculated for each sub-sample. The sub-samples are then combined in a joint analysis, treating them as independent observations. This leads to an improvement in performance parameters such as sensitivity, angular and energy resolution. Data loss is reduced since lower quality events are included in the analysis as well, rather than discarded. In this study, machine learning methods will be used to classify events according to their expected angular reconstruction quality. We will report the impact on CTA high-level performance when applying such an event-type classification, compared to the classical procedure.
Keywords: Cherenkov Telescope Array, very-high-energy gamma-rays, event-type based analysis
Published in RUNG: 18.09.2023; Views: 1907; Downloads: 9
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8. Extragalactic source population studies at very high energies in the Cherenkov Telescope Array eraT. Hassan, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, 2017, published scientific conference contribution Keywords: very high energy, CTA, extragalactic source
Published in RUNG: 16.02.2018; Views: 4361; Downloads: 141
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9. Layout design studies for medium-sized telescopes within the Cherenkov Telescope ArrayT. Hassan, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, 2015, published scientific conference contribution Keywords: Cherenkov Telescope Array (CTA), medium-sized telescopes (MST) CTA sub-array, MST layout design studies, Monte Carlo performance studies
Published in RUNG: 16.02.2017; Views: 5013; Downloads: 237
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10. Second large-scale Monte Carlo study for the Cherenkov Telescope ArrayT. Hassan, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, 2015, published scientific conference contribution Keywords: Cherenkov Telescope Array (CTA), CTA design optimization, Monte Carlo simulations
Published in RUNG: 16.02.2017; Views: 5281; Downloads: 204
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