TY  - JOUR
A1  - González, María Magdalena
A1  - Dorner, Daniela
A1  - Bretz, Thomas
A1  - García-González, José Andrés
T1  - Unbiased long-term monitoring at TeV energies
JF  - Galaxies
N2  - For the understanding of the variable, transient and non-thermal universe, unbiased long-term monitoring is crucial. To constrain the emission mechanisms at the highest energies, it is important to characterize the very high energy emission and its correlation with observations at other wavelengths. At very high energies, only a limited number of instruments is available. This article reviews the current status of monitoring of the extra-galactic sky at TeV energies.
KW  - monitoring
KW  - very high energies (VHE)
KW  - TeV energies
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-197389
SN  - 2075-4434
VL  - 7
IS  - 2
ER  - 
TY  - JOUR
A1  - Roelofs, Freek
A1  - Blackburn, Lindy
A1  - Lindahl, Greg
A1  - Doeleman, Sheperd S.
A1  - Johnson, Michael D.
A1  - Arras, Philipp
A1  - Chatterjee, Koushik
A1  - Emami, Razieh
A1  - Fromm, Christian
A1  - Fuentes, Antonio
A1  - Knollmüller, Jakob
A1  - Kosogorov, Nikita
A1  - Müller, Hendrik
A1  - Patel, Nimesh
A1  - Raymond, Alexander
A1  - Tiede, Paul
A1  - Traianou, Efthalia
A1  - Vega, Justin
T1  - The ngEHT analysis challenges
JF  - Galaxies
N2  - The next-generation Event Horizon Telescope (ngEHT) will be a significant enhancement of the Event Horizon Telescope (EHT) array, with ∼10 new antennas and instrumental upgrades of existing antennas. The increased uv-coverage, sensitivity, and frequency coverage allow a wide range of new science opportunities to be explored. The ngEHT Analysis Challenges have been launched to inform the development of the ngEHT array design, science objectives, and analysis pathways. For each challenge, synthetic EHT and ngEHT datasets are generated from theoretical source models and released to the challenge participants, who analyze the datasets using image reconstruction and other methods. The submitted analysis results are evaluated with quantitative metrics. In this work, we report on the first two ngEHT Analysis Challenges. These have focused on static and dynamical models of M87* and Sgr A* and shown that high-quality movies of the extended jet structure of M87* and near-horizon hourly timescale variability of Sgr A* can be reconstructed by the reference ngEHT array in realistic observing conditions using current analysis algorithms. We identify areas where there is still room for improvement of these algorithms and analysis strategies. Other science cases and arrays will be explored in future challenges.
KW  - very long baseline interferometry
KW  - black holes
KW  - active galactic nuclei
KW  - radio astronomy
KW  - imaging
KW  - instrument design
KW  - telescopes
KW  - algorithms
KW  - data analysis
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-304976
SN  - 2075-4434
VL  - 11
IS  - 1
ER  - 
TY  - JOUR
A1  - Dashkovskiy, Sergey
A1  - Slynko, Vitalii
T1  - Stability conditions for impulsive dynamical systems
JF  - Mathematics of Control, Signals, and Systems
N2  - In this work, we consider impulsive dynamical systems evolving on an infinite-dimensional space and subjected to external perturbations. We look for stability conditions that guarantee the input-to-state stability for such systems. Our new dwell-time conditions allow the situation, where both continuous and discrete dynamics can be unstable simultaneously. Lyapunov like methods are developed for this purpose. Illustrative finite and infinite dimensional examples are provided to demonstrate the application of the main results. These examples cannot be treated by any other published approach and demonstrate the effectiveness of our results.
KW  - lyapunov methods
KW  - stability
KW  - robustness
KW  - impulsive systems
KW  - infinite-dimensional systems
KW  - nonlinear systems
KW  - input-to-state stability
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-268390
SN  - 1435-568X
VL  - 34
IS  - 1
ER  - 
TY  - JOUR
A1  - Wang, Xiaoliang
A1  - Liu, Xuan
A1  - Xiao, Yun
A1  - Mao, Yue
A1  - Wang, Nan
A1  - Wang, Wei
A1  - Wu, Shufan
A1  - Song, Xiaoyong
A1  - Wang, Dengfeng
A1  - Zhong, Xingwang
A1  - Zhu, Zhu
A1  - Schilling, Klaus
A1  - Damaren, Christopher
T1  - On-orbit verification of RL-based APC calibrations for micrometre level microwave ranging system
JF  - Mathematics
N2  - Micrometre level ranging accuracy between satellites on-orbit relies on the high-precision calibration of the antenna phase center (APC), which is accomplished through properly designed calibration maneuvers batch estimation algorithms currently. However, the unmodeled perturbations of the space dynamic and sensor-induced uncertainty complicated the situation in reality; ranging accuracy especially deteriorated outside the antenna main-lobe when maneuvers performed. This paper proposes an on-orbit APC calibration method that uses a reinforcement learning (RL) process, aiming to provide the high accuracy ranging datum for onboard instruments with micrometre level. The RL process used here is an improved Temporal Difference advantage actor critic algorithm (TDAAC), which mainly focuses on two neural networks (NN) for critic and actor function. The output of the TDAAC algorithm will autonomously balance the APC calibration maneuvers amplitude and APC-observed sensitivity with an object of maximal APC estimation accuracy. The RL-based APC calibration method proposed here is fully tested in software and on-ground experiments, with an APC calibration accuracy of less than 2 mrad, and the on-orbit maneuver data from  11–12 April 2022, which achieved 1–1.5 mrad calibration accuracy after RL training. The proposed RL-based APC algorithm may extend to prove mass calibration scenes with actions feedback to attitude determination and control system (ADCS), showing flexibility of spacecraft payload applications in the future.
KW  - reinforcement learning
KW  - antenna phase center calibration
KW  - K band ranging (KBR)
KW  - micrometre level microwave ranging
KW  - MSC: 49M37
KW  - MSC: 65K05
KW  - MSC: 90C30
KW  - MSC: 90C40
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-303970
SN  - 2227-7390
VL  - 11
IS  - 4
ER  - 
TY  - JOUR
A1  - Renaut, Léo
A1  - Frei, Heike
A1  - Nüchter, Andreas
T1  - Lidar pose tracking of a tumbling spacecraft using the smoothed normal distribution transform
JF  - Remote Sensing
N2  - Lidar sensors enable precise pose estimation of an uncooperative spacecraft in close range. In this context, the iterative closest point (ICP) is usually employed as a tracking method. However, when the size of the point clouds increases, the required computation time of the ICP can become a limiting factor. The normal distribution transform (NDT) is an alternative algorithm which can be more efficient than the ICP, but suffers from robustness issues. In addition, lidar sensors are also subject to motion blur effects when tracking a spacecraft tumbling with a high angular velocity, leading to a loss of precision in the relative pose estimation. This work introduces a smoothed formulation of the NDT to improve the algorithm’s robustness while maintaining its efficiency. Additionally, two strategies are investigated to mitigate the effects of motion blur. The first consists in un-distorting the point cloud, while the second is a continuous-time formulation of the NDT. Hardware-in-the-loop tests at the European Proximity Operations Simulator demonstrate the capability of the proposed methods to precisely track an uncooperative spacecraft under realistic conditions within tens of milliseconds, even when the spacecraft tumbles with a significant angular rate.
KW  - pose tracking
KW  - uncooperative space rendezvous
KW  - lidar
KW  - normal distribution transform
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-313738
SN  - 2072-4292
VL  - 15
IS  - 9
ER  - 
TY  - JOUR
A1  - Adrián-Martínez, S.
A1  - Ageron, M.
A1  - Aharonian, F.
A1  - Aiello, S.
A1  - Albert, A.
A1  - Ameli, F.
A1  - Annasontzis, E.
A1  - Andre, M.
A1  - Androulakis, G.
A1  - Anghinolfi, M.
A1  - Anton, G.
A1  - Ardid, M.
A1  - Avgitas, T.
A1  - Barbarino, G.
A1  - Baret, B.
A1  - Barrios-Martí, J.
A1  - Belhorma, B.
A1  - Belias, A.
A1  - Berbee, A.
A1  - van den Berg, A.
A1  - Bertin, V.
A1  - Beurthey, S.
A1  - van Beeveren, V.
A1  - Beverini, N.
A1  - Biagi, S.
A1  - Biagioni, A.
A1  - Billault, M.
A1  - Bondì, M.
A1  - Bormuth, R.
A1  - Bouhadef, B.
A1  - Bourlis, G.
A1  - Bourret, S.
A1  - Boutonnet, C.
A1  - Bouwhuis, M.
A1  - Bozza, C.
A1  - Bruijn, R.
A1  - Brunner, J.
A1  - Buis, E.
A1  - Busto, J.
A1  - Cacopardo, G.
A1  - Caillat, L.
A1  - Calmai, M.
A1  - Calvo, D.
A1  - Capone, A.
A1  - Caramete, L.
A1  - Cecchini, S.
A1  - Celli, S.
A1  - Champion, C.
A1  - Cherkaoui El Moursli, R.
A1  - Cherubini, S.
A1  - Chiarusi, T.
A1  - Circella, M.
A1  - Classen, L.
A1  - Cocimano, R.
A1  - Coelho, J. A. B.
A1  - Coleiro, A.
A1  - Colonges, S.
A1  - Coniglione, R.
A1  - Cordelli, M.
A1  - Cosquer, A.
A1  - Coyle, P.
A1  - Creusot, A.
A1  - Cuttone, G.
A1  - D'Amico, A.
A1  - De Bonis, G.
A1  - De Rosa, G.
A1  - De Sio, C.
A1  - Di Capua, F.
A1  - Di Palma, I.
A1  - Díaz García, A. F.
A1  - Distefano, C.
A1  - Donzaud, C.
A1  - Dornic, D.
A1  - Dorosti-Hasankiadeh, Q.
A1  - Drakopoulou, E.
A1  - Drouhin, D.
A1  - Drury, L.
A1  - Durocher, M.
A1  - Eberl, T.
A1  - Eichie, S.
A1  - van Eijk, D.
A1  - El Bojaddaini, I.
A1  - El Khayati, N.
A1  - Elsaesser, D.
A1  - Enzenhöfer, A.
A1  - Fassi, F.
A1  - Favali, P.
A1  - Fermani, P.
A1  - Ferrara, G.
A1  - Filippidis, C.
A1  - Frascadore, G.
A1  - Fusco, L. A.
A1  - Gal, T.
A1  - Galatà, S.
A1  - Garufi, F.
A1  - Gay, P.
A1  - Gebyehu, M.
A1  - Giordano, V.
A1  - Gizani, N.
A1  - Gracia, R.
A1  - Graf, K.
A1  - Grégoire, T.
A1  - Grella, G.
A1  - Habel, R.
A1  - Hallmann, S.
A1  - van Haren, H.
A1  - Harissopulos, S.
A1  - Heid, T.
A1  - Heijboer, A.
A1  - Heine, E.
A1  - Henry, S.
A1  - Hernández-Rey, J. J.
A1  - Hevinga, M.
A1  - Hofestädt, J.
A1  - Hugon, C. M. F.
A1  - Illuminati, G.
A1  - James, C. W.
A1  - Jansweijer, P.
A1  - Jongen, M.
A1  - de Jong, M.
A1  - Kadler, M.
A1  - Kalekin, O.
A1  - Kappes, A.
A1  - Katz, U. F.
A1  - Keller, P.
A1  - Kieft, G.
A1  - Kießling, D.
A1  - Koffeman, E. N.
A1  - Kooijman, P.
A1  - Kouchner, A.
A1  - Kulikovskiy, V.
A1  - Lahmann, R.
A1  - Lamare, P.
A1  - Leisos, A.
A1  - Leonora, E.
A1  - Lindsey Clark, M.
A1  - Liolios, A.
A1  - Llorenz Alvarez, C. D.
A1  - Lo Presti, D.
A1  - Löhner, H.
A1  - Lonardo, A.
A1  - Lotze, M.
A1  - Loucatos, S.
A1  - Maccioni, E.
A1  - Mannheim, K.
A1  - Margiotta, A.
A1  - Marinelli, A.
A1  - Mariş, O.
A1  - Markou, C.
A1  - Martínez-Mora, J. A.
A1  - Martini, A.
A1  - Mele, R.
A1  - Melis, K. W.
A1  - Michael, T.
A1  - Migliozzi, P.
A1  - Migneco, E.
A1  - Mijakowski, P.
A1  - Miraglia, A.
A1  - Mollo, C. M.
A1  - Mongelli, M.
A1  - Morganti, M.
A1  - Moussa, A.
A1  - Musico, P.
A1  - Musumeci, M.
A1  - Navas, S.
A1  - Nicoleau, C. A.
A1  - Olcina, I.
A1  - Olivetto, C.
A1  - Orlando, A.
A1  - Papaikonomou, A.
A1  - Papaleo, R.
A1  - Păvălaş, G. E.
A1  - Peek, H.
A1  - Pellegrino, C.
A1  - Perrina, C.
A1  - Pfutzner, M.
A1  - Piattelli, P.
A1  - Pikounis, K.
A1  - Poma, G. E.
A1  - Popa, V.
A1  - Pradier, T.
A1  - Pratolongo, F.
A1  - Pühlhofer, G.
A1  - Pulvirenti, S.
A1  - Quinn, L.
A1  - Racca, C.
A1  - Raffaelli, F.
A1  - Randazzo, N.
A1  - Rapidis, P.
A1  - Razis, P.
A1  - Real, D.
A1  - Resvanis, L.
A1  - Reubelt, J.
A1  - Riccobene, G.
A1  - Rossi, C.
A1  - Rovelli, A.
A1  - Saldaña, M.
A1  - Salvadori, I.
A1  - Samtleben, D. F. E.
A1  - Sánchez García, A.
A1  - Sánchez Losa, A.
A1  - Sanguineti, M.
A1  - Santangelo, A.
A1  - Santonocito, D.
A1  - Sapienza, P.
A1  - Schimmel, F.
A1  - Schmelling, J.
A1  - Sciacca, V.
A1  - Sedita, M.
A1  - Seitz, T.
A1  - Sgura, I.
A1  - Simeone, F.
A1  - Siotis, I.
A1  - Sipala, V.
A1  - Spisso, B.
A1  - Spurio, M.
A1  - Stavropoulos, G.
A1  - Steijger, J.
A1  - Stellacci, S. M.
A1  - Stransky, D.
A1  - Taiuti, M.
A1  - Tayalati, Y.
A1  - Tézier, D.
A1  - Theraube, S.
A1  - Thompson, L.
A1  - Timmer, P.
A1  - Tönnis, C.
A1  - Trasatti, L.
A1  - Trovato, A.
A1  - Tsirigotis, A.
A1  - Tzamarias, S.
A1  - Tzamariudaki, E.
A1  - Vallage, B.
A1  - Van Elewyk, V.
A1  - Vermeulen, J.
A1  - Vicini, P.
A1  - Viola, S.
A1  - Vivolo, D.
A1  - Volkert, M.
A1  - Voulgaris, G.
A1  - Wiggers, L.
A1  - Wilms, J.
A1  - de Wolf, E.
A1  - Zachariadou, K.
A1  - Zornoza, J. D.
A1  - Zúñiga, J.
T1  - Letter of intent for KM3NeT 2.0
JF  - Journal of Physics G-Nuclear and Particle Physics
N2  - The main objectives of the KM3NeT Collaboration are (i) the discovery and subsequent observation of high-energy neutrino sources in the Universe and (ii) the determination of the mass hierarchy of neutrinos. These objectives are strongly motivated by two recent important discoveries, namely: (1) the high-energy astrophysical neutrino signal reported by IceCube and (2) the sizable contribution of electron neutrinos to the third neutrino mass eigenstate as reported by Daya Bay, Reno and others. To meet these objectives, the KM3NeT Collaboration plans to build a new Research Infrastructure consisting of a network of deep-sea neutrino telescopes in the Mediterranean Sea. A phased and distributed implementation is pursued which maximises the access to regional funds, the availability of human resources and the synergistic opportunities for the Earth and sea sciences community. Three suitable deep-sea sites are selected, namely off-shore Toulon (France), Capo Passero (Sicily, Italy) and Pylos (Peloponnese, Greece). The infrastructure will consist of three so-called building blocks. A building block comprises 115 strings, each string comprises 18 optical modules and each optical module comprises 31 photo-multiplier tubes. Each building block thus constitutes a three-dimensional array of photo sensors that can be used to detect the Cherenkov light produced by relativistic particles emerging from neutrino interactions. Two building blocks will be sparsely configured to fully explore the IceCube signal with similar instrumented volume, different methodology, improved resolution and
KW  - neutrino astronomy
KW  - eutrino physics
KW  - deep sea neutrino telescope
KW  - neutrino mass hierarchy
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188050
VL  - 43
IS  - 8
ER  - 
TY  - JOUR
A1  - Johnson, Michael D.
A1  - Akiyama, Kazunori
A1  - Blackburn, Lindy
A1  - Bouman, Katherine L.
A1  - Broderick, Avery E.
A1  - Cardoso, Vitor
A1  - Fender, Rob P.
A1  - Fromm, Christian M.
A1  - Galison, Peter
A1  - Gómez, José L.
A1  - Haggard, Daryl
A1  - Lister, Matthew L.
A1  - Lobanov, Andrei P.
A1  - Markoff, Sera
A1  - Narayan, Ramesh
A1  - Natarajan, Priyamvada
A1  - Nichols, Tiffany
A1  - Pesce, Dominic W.
A1  - Younsi, Ziri
A1  - Chael, Andrew
A1  - Chatterjee, Koushik
A1  - Chaves, Ryan
A1  - Doboszewski, Juliusz
A1  - Dodson, Richard
A1  - Doeleman, Sheperd S.
A1  - Elder, Jamee
A1  - Fitzpatrick, Garret
A1  - Haworth, Kari
A1  - Houston, Janice
A1  - Issaoun, Sara
A1  - Kovalev, Yuri Y.
A1  - Levis, Aviad
A1  - Lico, Rocco
A1  - Marcoci, Alexandru
A1  - Martens, Niels C. M.
A1  - Nagar, Neil M.
A1  - Oppenheimer, Aaron
A1  - Palumbo, Daniel C. M.
A1  - Ricarte, Angelo
A1  - Rioja, María  J.
A1  - Roelofs, Freek
A1  - Thresher, Ann C.
A1  - Tiede, Paul
A1  - Weintroub, Jonathan
A1  - Wielgus, Maciek
T1  - Key science goals for the next-generation Event Horizon Telescope
JF  - Galaxies
N2  - The Event Horizon Telescope (EHT) has led to the first images of a supermassive black hole, revealing the central compact objects in the elliptical galaxy M87 and the Milky Way. Proposed upgrades to this array through the next-generation EHT (ngEHT) program would sharply improve the angular resolution, dynamic range, and temporal coverage of the existing EHT observations. These improvements will uniquely enable a wealth of transformative new discoveries related to black hole science, extending from event-horizon-scale studies of strong gravity to studies of explosive transients to the cosmological growth and influence of supermassive black holes. Here, we present the key science goals for the ngEHT and their associated instrument requirements, both of which have been formulated through a multi-year international effort involving hundreds of scientists worldwide.
KW  - black holes
KW  - general relativity
KW  - interferometry
KW  - accretion
KW  - relativistic jets
KW  - very-long-baseline interferometry
KW  - EHT
KW  - ngEHT
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-313525
SN  - 2075-4434
VL  - 11
IS  - 3
ER  - 
TY  - JOUR
A1  - Gedalin, Michael
A1  - Dröge, Wolfgang
T1  - Ion dynamics in quasi-perpendicular collisionless interplanetary shocks: a case study
JF  - Frontiers in Physics
N2  - Interplanetary shocks are believed to play an important role in the acceleration of charged particles in the heliosphere. While the acceleration to high energies proceeds via the diffusive mechanism at the scales exceeding by far the shock width, the initial stage (injection) should occur at the shock itself. Numerical tracing of ions is done in a model quasi-perpendicular shock front with a typical interplanetary shock parameters (Mach number, upstream ion temperature). The analysis of the distribution of the transmitted solar wind is used to adjust the cross-shock potential which is not directly measured. It is found that, for typical upstream ion temperatures, acceleration of the ions from the tail of the solar wind distribution is unlikely. Pickup ions with a shell distribution are found to be effectively energized and may be injected into further diffusive acceleration regime. Pre-accelerated ions are efficiently upscaled in energies. A part of these ions is returned to the upstream region where they can further be diffusively accelerated.
KW  - collisionless shocks
KW  - particle acceleration
KW  - non-linear waves
KW  - ion dynamics
KW  - heliospheric shocks
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-189407
SN  - 2296-424X
VL  - 1
ER  - 
TY  - JOUR
A1  - Dorner, Daniela
A1  - Mostafá, Miguel
A1  - Satalecka, Konstancja
T1  - High-energy alerts in the multi-messenger era
JF  - Universe
N2  - The observation of electromagnetic counterparts to both high energy neutrinos and gravitational waves marked the beginning of a new era in astrophysics. The multi-messenger approach allows us to gain new insights into the most energetic events in the Universe such as gamma-ray bursts, supernovas, and black hole mergers. Real-time multi-messenger alerts are the key component of the observational strategies to unravel the transient signals expected from astrophysical sources. Focusing on the high-energy regime, we present a historical perspective of multi-messenger observations, the detectors and observational techniques used to study them, the status of the multi-messenger alerts and the most significant results, together with an overview of the future prospects in the field.
KW  - multi-messenger
KW  - real-time
KW  - high-energy
KW  - alerts
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-248496
SN  - 2218-1997
VL  - 7
IS  - 11
ER  - 
TY  - JOUR
A1  - Morais, António P.
A1  - Pasechnik, Roman
A1  - Porod, Werner
T1  - Grand Unified origin of gauge interactions and families replication in the Standard Model
JF  - Universe
N2  - The tremendous phenomenological success of the Standard Model (SM) suggests that its flavor structure and gauge interactions may not be arbitrary but should have a fundamental first-principle explanation. In this work, we explore how the basic distinctive properties of the SM dynamically emerge from a unified New Physics framework tying together both flavor physics and Grand Unified Theory (GUT) concepts. This framework is suggested by a novel anomaly-free supersymmetric chiral E\(_6\)×SU(2)\(_F\)×U(1)\(_F\) GUT containing the SM. Among the most appealing emergent properties of this theory is the Higgs-matter unification with a highly-constrained massless chiral sector featuring two universal Yukawa couplings close to the GUT scale. At the electroweak scale, the minimal SM-like effective field theory limit of this GUT represents a specific flavored three-Higgs doublet model consistent with the observed large hierarchies in the quark mass spectra and mixing already at tree level.
KW  - grand unified theories
KW  - supersymmetry
KW  - phenomenology of New Physics
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-250237
SN  - 2218-1997
VL  - 7
IS  - 12
ER  - 
TY  - JOUR
A1  - Romoli, Carlo
A1  - Chakraborty, Nachiketa
A1  - Dorner, Daniela
A1  - Taylor, Andrew
A1  - Blank, Michael
T1  - Flux Distribution of Gamma-Ray Emission in Blazars: The Example of Mrk 501
JF  - Galaxies
N2  - Flux distribution is an important tool to understand the variability processes in activegalactic nuclei. We now have available a great deal of observational evidences pointing towards thepresence of log-normal components in the high energy light curves, and different models have beenproposed to explain these data. Here, we collect some of the recent developments on this topic usingthe well-known blazar Mrk 501 as example of complex and interesting aspects coming from its fluxdistribution in different energy ranges and at different timescales. The observational data we refer toare those collected in a complementary manner by Fermi-LAT over multiple years, and by the FirstG-APD Cherenkov Telescope (FACT) telescope and the H.E.S.S. array in correspondence of the brightflare of June 2014
KW  - gamma rays
KW  - very high energy
KW  - active galactic nuclei
KW  - Markarian 501
KW  - monitoring
KW  - flux distributions
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-197580
SN  - 2075-4434
VL  - 6
IS  - 4
ER  - 
TY  - JOUR
A1  - Chatterjee, Koushik
A1  - Chael, Andrew
A1  - Tiede, Paul
A1  - Mizuno, Yosuke
A1  - Emami, Razieh
A1  - Fromm, Christian
A1  - Ricarte, Angelo
A1  - Blackburn, Lindy
A1  - Roelofs, Freek
A1  - Johnson, Michael D.
A1  - Doeleman, Sheperd S.
A1  - Arras, Philipp
A1  - Fuentes, Antonio
A1  - Knollmüller, Jakob
A1  - Kosogorov, Nikita
A1  - Lindahl, Greg
A1  - Müller, Hendrik
A1  - Patel, Nimesh
A1  - Raymond, Alexander
A1  - Traianou, Efthalia
A1  - Vega, Justin
T1  - Accretion flow morphology in numerical simulations of black holes from the ngEHT model library: the impact of radiation physics
JF  - Galaxies
N2  - In the past few years, the Event Horizon Telescope (EHT) has provided the first-ever event horizon-scale images of the supermassive black holes (BHs) M87* and Sagittarius A* (Sgr A*). The next-generation EHT project is an extension of the EHT array that promises larger angular resolution and higher sensitivity to the dim, extended flux around the central ring-like structure, possibly connecting the accretion flow and the jet. The ngEHT Analysis Challenges aim to understand the science extractability from synthetic images and movies to inform the ngEHT array design and analysis algorithm development. In this work, we compare the accretion flow structure and dynamics in numerical fluid simulations that specifically target M87* and Sgr A*, and were used to construct the source models in the challenge set. We consider (1) a steady-state axisymmetric radiatively inefficient accretion flow model with a time-dependent shearing hotspot, (2) two time-dependent single fluid general relativistic magnetohydrodynamic (GRMHD) simulations from the H-AMR code, (3) a two-temperature GRMHD simulation from the BHAC code, and (4) a two-temperature radiative GRMHD simulation from the KORAL code. We find that the different models exhibit remarkably similar temporal and spatial properties, except for the electron temperature, since radiative losses substantially cool down electrons near the BH and the jet sheath, signaling the importance of radiative cooling even for slowly accreting BHs such as M87*. We restrict ourselves to standard torus accretion flows, and leave larger explorations of alternate accretion models to future work.
KW  - black holes
KW  - general relativity
KW  - accretion
KW  - relativistic jets
KW  - very-long-baseline interferometry
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-304084
SN  - 2075-4434
VL  - 11
IS  - 2
ER  - 
TY  - JOUR
A1  - Kraus, Daniela
A1  - Moucha, Annika
A1  - Roth, Oliver
T1  - A sharp Bernstein–type inequality and application to the Carleson embedding theorem with matrix weights
JF  - Analysis and Mathematical Physics
N2  - We prove a sharp Bernstein-type inequality for complex polynomials which are positive and satisfy a polynomial growth condition on the positive real axis. This leads to an improved upper estimate in the recent work of Culiuc and Treil (Int. Math. Res. Not. 2019: 3301–3312, 2019) on the weighted martingale Carleson embedding theorem with matrix weights. In the scalar case this new upper bound is optimal.
KW  - Bernstein-type inequality
KW  - complex polynomials
KW  - Carleson embedding theorem
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-270485
SN  - 1664-235X
VL  - 12
IS  - 1
ER  -