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27 results on '"Maximilian, Noethe"'

1. Fractional Variability—A Tool to Study Blazar Variability

Author

Bernd Schleicher, Axel Arbet-Engels, Dominik Baack, Matteo Balbo, Adrian Biland, Michael Blank, Thomas Bretz, Kai Bruegge, Michael Bulinski, Jens Buss, Manuel Doerr, Daniela Dorner, Dominik Elsaesser, Sergej Grischagin, Dorothee Hildebrand, Lena Linhoff, Karl Mannheim, Sebastian Achim Mueller, Dominik Neise, Andrii Neronov, Maximilian Noethe, Aleksander Paravac, Wolfgang Rhode, Florian Schulz, Kevin Sedlaczek, Amit Shukla, Vitalii Sliusar, Elan von Willert, and Roland Walter

Subjects
blazars, variability, fractional variability, active galactic nuclei, Astronomy, QB1-991
Abstract

Active Galactic Nuclei emit radiation over the whole electromagnetic spectrum up to TeV energies. Blazars are one subtype with their jets pointing towards the observer. One of their typical features is extreme variability on timescales, from minutes to years. The fractional variability is an often used parameter for investigating the degree of variability of a light curve. Different detection methods and sensitivities of the instruments result in differently binned data and light curves with gaps. As they can influence the physics interpretation of the broadband variability, the effects of these differences on the fractional variability need to be studied. In this paper, we study the systematic effects of completeness in time coverage and the sampling rate. Using public data from instruments monitoring blazars in various energy ranges, we study the variability of the bright TeV blazars Mrk 421 and Mrk 501 over the electromagnetic spectrum, taking into account the systematic effects, and compare our findings with previous results. Especially in the TeV range, the fractional variability is higher than in previous studies, which can be explained by the much longer (seven years compared to few weeks) and more complete data sample.

Published
2019
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2. Flux States of Active Galactic Nuclei

Author

Daniela Dorner, Axel Arbet-Engels, Dominik Baack, Matteo Balbo, Adrian Biland, Michael Blank, Thomas Bretz, Kai Bruegge, Michael Bulinski, Jens Buss, Manuel Doerr, Dominik Elsaesser, Dorothee Hildebrand, Lena Linhoff, Karl Mannheim, Sebastian Achim Mueller, Dominik Neise, Andrii Neronov, Maximilian Noethe, Aleksander Paravac, Wolfgang Rhode, Bernd Schleicher, Florian Schulz, Kevin Sedlaczek, Amit Shukla, Vitalii Sliusar, Elan von Willert, Roland Walter, and FACT Collaboration

Subjects
active galactic nuclei, blazars, monitoring, TeV energies, FACT, flux states, flux distributions, duty cycle, Astronomy, QB1-991
Abstract

Blazars are known to show variability on time scales from minutes to years covering a wide range of flux states. Studying the flux distribution of a source allows for various insights. The shape of the flux distribution can provide information on the nature of the underlying variability processes. The level of a possible quiescent state can be derived from the main part of the distribution that can be described by a Gaussian distribution. Dividing the flux states into quiescent and active, the duty cycle of a source can be calculated. Finally, this allows alerting the multi-wavelength and multi-messenger community in case a source is in an active state. To get consistent and conclusive results from flux distributions, unbiased long-term observations are crucial. Only like this is a complete picture of the variability and flux states, e.g., an all-time quiescent state, possible. In seven years of monitoring of bright TeV blazars, the first G-APD Cherenkov telescope (FACT) has collected a total of more than 11,700 hours of physics data with 1500 hours to 3000 hours per source for Mrk 421, Mrk 501, 1ES 1959+650, and 1ES 2344+51.

Published
2019
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3. Rapid X-ray Variability in Mkn 421 during a Multiwavelength Campaign

Author

Alex G Markowitz, Krzysztof Nalewajko, Gopal Bhatta, Gulab C Dewangan, Sunil Chandra, Daniela Dorner, Bernd Schleicher, Urszula Pajdosz-Śmierciak, Łukasz Stawarz, Staszek Zola, Michał Ostrowski, Daniele Carosati, Saikruba Krishnan, Rumen Bachev, Erika Benítez, Kosmas Gazeas, David Hiriart, Shao-Ming Hu, Valeri Larionov, Alessandro Marchini, Katsura Matsumoto, A A Nikiforova, Tapio Pursimo, Claudia M Raiteri, Daniel E Reichart, Diego Rodriguez, Evgeni Semkov, Anton Strigachev, Yuki Sugiura, Massimo Villata, James R Webb, Axel Arbet-Engels, Dominik Baack, Matteo Balbo, Adrian Biland, Thomas Bretz, Jens Buss, Laura Eisenberger, Dominik Elsaesser, Dorothee Hildebrand, Roman Iotov, Adelina Kalenski, Karl Mannheim, Alison Mitchell, Dominik Neise, Maximilian Noethe, Aleksander Paravac, Wolfgang Rhode, Vitalii Sliusar, and Roland Walter

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, black hole physics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Mkn 421 [BL Lacertae objects], Astrophysics - Astrophysics of Galaxies, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), active [galaxies], Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics, acceleration of particles
Abstract

The study of short-term variability properties in AGN jets has the potential to shed light on their particle acceleration and emission mechanisms. We report results from a four-day coordinated multi-wavelength campaign on the highly-peaked blazar (HBL) Mkn 421 in 2019 January. We obtained X-ray data from AstroSAT, BVRI photometry with the Whole Earth Blazar Telescope (WEBT), and TeV data from FACT to explore short-term multi-wavelength variability in this HBL. The X-ray continuum is rapidly variable on time-scales of tens of ks. Fractional variability amplitude increases with energy across the synchrotron hump, consistent with previous studies; we interpret this observation in the context of a model with multiple cells whose emission spectra contain cutoffs that follow a power-law distribution. We also performed time-averaged and time-resolved (time-scales of 6 ks) spectral fits; a broken power-law model fits all spectra well; time-resolved spectral fitting reveals the usual hardening when brightening behaviour. Intra-X-ray cross correlations yield evidence for the 0.6-0.8 keV band to likely lead the other bands by an average of 4.6 +- 2.6 ks, but only during the first half of the observation. The source displayed minimal night-to-night variability at all wavebands thus precluding significant interband correlations during our campaign. The broadband SED is modeled well with a standard one-zone leptonic model, yielding jet parameters consistent with those obtained from previous SEDs of this source., This article has been accepted for publication in The Monthly Notices of the Royal Astronomical Society (2022), and is published in Volume 513, Issue 2, pp.1662-1679. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. 19 pages; 12 figures

Published
2022

4. Searching for VHE gamma-ray emission associated with IceCube neutrino alerts using FACT, H.E.S.S., MAGIC, and VERITAS

Author

Konstancja, Satalecka, Acciari, Victor A., Stefano, Ansoldi, Lucio Angelo Antonelli, Axel Arbet Engels, Manuel, Artero, Katsuaki, Asano, Dominik, Baack, Ana, Babic, Andr('(e))s, Baquero, Ulisses Barres de Almeida, Juan Abel Barrio, Ivana, Batkovi('(c)), Josefa Becerra Gonzalez, Wlodek, Bednarek, Lorenzo, Bellizzi, Elisa, Bernardini, Maria-Isabel, Bernardos, Alessio, Berti, Jürgen, Besenrieder, Wrijupan, Bhattacharyya, Ciro, Bigongiari, Adrian, Biland, Oscar, Blanch, Hendrik, Bökenkamp, Giacomo, Bonnoli, Zeljka, Bosnjak, Giovanni, Busetto, Roberto, Carosi, Giovanni, Ceribella, Matteo, Cerruti, Yating, Chai, Ashot, Chilingarian, Stefan, Cikota, Sidika Merve Colak, Eduardo, Colombo, Jose Luis Contreras, Juan, Cortina, Stefano, Covino, Giacomo D( extquotesingle)Amico, Valerio D( extquotesingle)Elia, Paolo Da Vela, Francesco, Dazzi, Alessandro De Angelis, Barbara De Lotto, Manuel, Delfino, Jordi, Delgado, Carlos Delgado Mendez, Davide, Depaoli, Federico Di Pierro, Leonardo Di Venere, Elia Do Souto Espi(~(n))eira, Dijana Dominis Prester, Alice, Donini, Daniela, Dorner, Michele, Doro, Dominik, Elsaesser, Vandad Fallah Ramazani, Alicia, Fattorini, Maria Victoria Fonseca, Lluis, Font, Christian, Fruck, Satoshi, Fukami, Yasushi, Fukazawa, Garc('(i))a L('(o))pez, Ramon J., Markus, Garczarczyk, Sargis, Gasparyan, Markus, Gaug, Giglietto, Nicola, Francesco, Giordano, Pawel, Gliwny, Nikola, Godinovic, David, Green, Jarred Gershon Green, Daniela, Hadasch, Alexander, Hahn, Lea, Heckmann, Javier, Herrera, John, Hoang, Dario, Hrupec, Moritz, Hütten, Tomohiro, Inada, Kazuma, Ishio, Yuki, Iwamura, Irene Jim('(e))nez Mart('(i))nez, Jenni, Jormanainen, L('(e))a, Jouvin, Marie, Karjalainen, Daniel, Kerszberg, Yukiho, Kobayashi, Hidetoshi, Kubo, Junko, Kushida, Alessandra, Lamastra, Damir, Lelas, Francesco, Leone, Elina, Lindfors, Lena, Linhoff, Saverio, Lombardi, Francesco, Longo, Ruben, Lopez-Coto, Marcos, L('(o))pez-Moya, Alicia, L('(o))pez-Oramas, Loporchio, Serena, Bernardo Machado de Oliveira Fraga, Camilla, Maggio, Pratik, Majumdar, Martin, Makariev, Manuela, Mallamaci, Galina, Maneva, Marina, Manganaro, Karl, Mannheim, Laura, Maraschi, Mos(`(e)), Mariotti, Manel, Martinez, Daniel, Mazin, Stefano, Menchiari, Simone, Mender, Sa( (s))a Mi('(c))anovi('(c)), Davide, Miceli, Tjark, Miener, Jose Miguel Miranda, Razmik, Mirzoyan, Edgar, Molina, Abelardo, Moralejo, Daniel, Morcuende, Victoria, Moreno, Elena, Moretti, Takeshi, Nakamori, Lara, Nava, Vitaly, Neustroev, Cosimo, Nigro, Kari, Nilsson, Kyoshi, Nishijima, Koji, Noda, Seiya, Nozaki, Yoshiki, Ohtani, Tomohiko, Oka, Jorge, Otero-Santos, Simona, Paiano, Michele, Palatiello, David, Paneque, Riccardo, Paoletti, Paredes, Josep M., Lovro, Pavleti('(c)), Pablo, Pe(~(n))il, Massimo, Persic, Marine, Pihet, Pier Giorgio Prada Moroni, Elisa, Prandini, Chaitanya, Priyadarshi, Ivica, Puljak, Wolfgang, Rhode, Marc, Rib('(o)), Javier, Rico, Chiara, Righi, Andrea, Rugliancich, Narek, Sahakyan, Takayuki, Saito, Shunsuke, Sakurai, Francesco Gabriele Saturni, Bernd, Schleicher, Kevin, Schmidt, Thomas, Schweizer, Julian, Sitarek, Iva, ( (S))nidari('(c)), Dorota, Sobczy('(n))ska, Alessia, Spolon, Antonio, Stamerra, Jelena Stri( (s))kovi('(c)), Derek, Strom, Marcel, Strzys, Yusuke, Suda, Tihomir, Suri('(c)), Mitsunari, Takahashi, Ryuji, Takeishi, Fabrizio, Tavecchio, Petar, Temnikov, Tomislav, Terzic, Masahiro, Teshima, Luca, Tosti, Stefano, Truzzi, Antonio, Tutone, Santiago, Ubach, Juliane van Scherpenberg, Gaia, Vanzo, Monica VAZQUEZ ACOSTA, Sofia, Ventura, Vassil, Verguilov, Carlo Francesco Vigorito, Vincenzo, Vitale, Ievgen, Vovk, Martin, Will, Carolin, Wunderlich, Tokonatsu, Yamamoto, Darko, Zari('(c)), Matteo, Balbo, Thomas, Bretz, Jens, Buss, Laura, Eisenberger, Dorothee, Hildebrand, Roman, Iotov, Adelina, Kalenski, Dominik, Neise, Maximilian, Noethe, Aleksander, Paravac, Vitalii, Sliusar, Roland, Walter, Rasha, Abbasi, Markus, Ackermann, Jenni, Adams, Juanan, Aguilar, Ahlers, M., Maryon, Ahrens, Cyril Martin Alispach, Antonio Augusto Alves Junior, Najia Moureen Binte Amin, Rui, An, Karen, Andeen, Tyler, Anderson, Gisela, Anton, Carlos, Arguelles, Yosuke, Ashida, Spencer, Axani, Xinhua, Bai, Aswathi Balagopal, V., Anastasia Maria Barbano, Barwick, S. W., Benjamin, Bastian, Vedant, Basu, Sebastian, Baur, Bay, R. C., Beatty, J. J., Becker, K. -H., Julia Becker Tjus, Chiara, Bellenghi, Segev, Benzvi, Berley, D., Besson, D. Z., Gary, Binder, Daniel, Bindig, Blaufuss, E., Summer, Blot, Matthias, Boddenberg, Federico, Bontempo, Jurgen, Borowka, Boser, S., Olga, Botner, Jakob, Bottcher, Etienne, Bourbeau, Federica, Bradascio, Braun, J., Stephanie, Bron, Jannes, Brostean-Kaiser, Sally-Ann, Browne, Alexander, Burgman, Ryan, Burley, Raffaela, Busse, Michael, Campana, Erin, Carnie-Bronca, Chujie, Chen, Dmitry, Chirkin, Koun, Choi, Bryanlee, Clark, Kenneth, Clark, Lew, Classen, Alan, Coleman, Gabriel, Collin, Conrad, J. M., Paul, Coppin, Pablo, Correa, Cowen, D. F., Cross, R., Christian, Dappen, Pranav, Dave, Catherine DE CLERCQ, James, Delaunay, Hans, Dembinski, Kunal, Deoskar, Sam De Ridder, Abhishek, Desai, Paolo, Desiati, Krijn de Vries, Gwenhaël de Wasseige, Meike De With, Tyce, Deyoung, Sukeerthi, Dharani, Alejandro, Diaz, Juan Carlos Diaz-Velez, Markus, Dittmer, Hrvoje, Dujmovic, Matt, Dunkman, Michael, Duvernois, Emily, Dvorak, Thomas, Ehrhardt, Philipp, Eller, Ralph, Engel, Hannah, Erpenbeck, John, Evans, Evenson, P. A., Kwok Lung Fan, Fazely, A. R., Sebastian, Fiedlschuster, Aaron, Fienberg, Kirill, Filimonov, Chad, Finley, Leander, Fischer, Derek, B Fox, Anna, Franckowiak, Elizabeth, Friedman, Alexander, Fritz, Philipp, Furst, Gaisser, T. K., Jay, Gallagher, Erik, Ganster, Alfonso, Garcia, Simone, Garrappa, Gerhardt, L., Ava, Ghadimi, Christian, Glaser, Theo, Glauch, Thorsten, Glusenkamp, Goldschmidt, A., Javier, Gonzalez, Sreetama, Goswami, Darren, Grant, Timoth('(e))e, Gr('(e))goire, Spencer, Griswold, Mehmet, Gunduz, Christoph, Günther, Christian, Haack, Allan, Hallgren, Halliday, R., Halve, L., Halzen, F., Martin Ha Minh, Kael, Hanson, John, Hardin, Harnisch, Alexander A., Andreas, Haungs, Simon, Hauser, Dustin, Hebecker, Helbing, K., Felix, Henningsen, Hettinger, Emma C., Stephanie, Hickford, Joshua, Hignight, Colton, Hill, Hill, G. C., Kara, Hoffman, Ruth, Hoffmann, Tobias, Hoinka, Benjamin, Hokanson-Fasig, Hoshina, K., Feifei, Huang, Matthias, Huber, Thomas, Huber, Klas, Hultqvist, Mirco, Hunnefeld, Raamis, Hussain, Seongjin, In, Nad(`(e))ge, Iovine, Aya, Ishihara, Matti, Jansson, George, Japaridze, Minjin, Jeong, Ben, Jones, Donghwa, Kang, Woosik, Kang, Xinyue, Kang, Alexander, Kappes, David, Kappesser, Timo, Karg, Martina, Karl, Karle, A., Katz, U., Kauer, M., Moritz, Kellermann, Kelley, J. L., Ali, Kheirandish, Ken( extquotesingle)ichi Kin, Thomas, Kintscher, Joanna, Kiryluk, Spencer, Klein, Ramesh, Koirala, Hermann, Kolanoski, Tomas, Kontrimas, Lutz, Kopke, Claudio, Kopper, Sandro, Kopper, Koskinen, D. J., Paras, Koundal, Michael, Kovacevich, Marek, Kowalski, Tetiana, Kozynets, Emma, Kun, Naoko, Kurahashi, Neha, Lad, Cristina Lagunas Gualda, Justin, Lanfranchi, Michael, J Larson, Frederik Hermann Lauber, Jeffrey, Lazar, Jiwoong, Lee, Kayla, Leonard, Agnieszka, Leszczy('(n))ska, Yijia, Li, Massimiliano, Lincetto, Qinrui, Liu, Maria, Liubarska, Elisa, Lohfink, Cristian Jesus Lozano Mariscal, Lu, Lu, Francesco, Lucarelli, Andrew, Ludwig, William, Luszczak, Yang, Lyu, Wing Yan Ma, James, Madsen, Kendall, Mahn, Yuya, Makino, Sarah, Mancina, Ioana Codrina Maris, Maruyama, Reina H., Mase, K., Thomas, Mcelroy, Frank, Mcnally, James Vincent Mead, Meagher, K., Andres, Medina, Maximilian, Meier, Stephan, Meighen-Berger, Jessie, Micallef, Daniela, Mockler, Teresa, Montaruli, Roger, Moore, Morse, R., Marjon, Moulai, Richard, Naab, Ryo, Nagai, Uwe, Naumann, Jannis, Necker, Le Viet Nguyen, Hans, Niederhausen, Mehr, Nisa, Sarah, Nowicki, Dave, Nygren, Anna Obertacke Pollmann, Marie, Oehler, Olivas, A., Erin O( extquotesingle)Sullivan, Hershal, Pandya, Daria, Pankova, Nahee, Park, Grant, Parker, Ek Narayan Paudel, Larissa, Paul, Carlos Perez de los Heros, Lilly, Peters, Saskia, Philippen, Damian, Pieloth, Sarah, Pieper, Martin, Pittermann, Pizzuto, A., Plum, M., Yuiry, Popovych, Alessio, Porcelli, Maria Prado Rodriguez, Buford Price, P., Brandom, Pries, Gerald, Przybylski, Christoph, Raab, Amirreza, Raissi, Mohamed, Rameez, Rawlins, K., Immacolata Carmen Rea, Abdul, Rehman, Ren('(e)), Reimann, Giovanni, Renzi, Elisa, Resconi, Simeon, Reusch, Mike, Richman, Benedikt, Riedel, Ella, Roberts, Sally, Robertson, Gerrit, Roellinghoff, Martin, Rongen, Carsten, Rott, Tim, Ruhe, Dirk, Ryckbosch, Devyn Rysewyk Cantu, Ibrahim, Safa, Julian, Saffer, Sebastian Sanchez Herrera, Alexander, Sandrock, Joakim, Sandroos, Marcos, Santander, Subir, Sarkar, Sourav, Sarkar, Maximilian Karl Scharf, Merlin, Schaufel, Harald, Schieler, Sebastian, Schindler, Schlunder, P., Torsten, Schmidt, Austin, Schneider, Judith, Schneider, Schröder, Frank G., Lisa Johanna Schumacher, Georg, Schwefer, Steve, Sclafani, Seckel, D., Surujhdeo, Seunarine, Ankur, Sharma, Shefali, Shefali, Manuel, Silva, Barbara, Skrzypek, Ben, Smithers, Robert, Snihur, Jan, Soedingrekso, Dennis, Soldin, Christian, Spannfellner, Glenn, Spiczak, Christian, Spiering, Juliana, Stachurska, Michael, Stamatikos, Stanev, T., Robert, Stein, Joeran, Stettner, Steuer, A., Stezelberger, T., Timo, Sturwald, Thomas, Stuttard, Sullivan, G. W., Taboada, I., Frederik, Tenholt, Samvel, Ter-Antonyan, Tilav, S., Franziska, Tischbein, Kirsten, Tollefson, Christoph, Tönnis, Simona, Toscano, Delia, Tosi, Alexander, Trettin, Maria, Tselengidou, Chunfai, Tung, Andrea, Turcati, Roxanne, Turcotte, Colin, Turley, Jean Pierre Twagirayezu, Bunheng, Ty, Martin Unland Elorrieta, Nora, Valtonen-Mattila, Justin, Vandenbroucke, Nick van Eijndhoven, David, Vannerom, Jakob van Santen, Stef, Verpoest, Matthias, Vraeghe, Walck, C., Timothyblake, Watson, Chris, Weaver, Philip, Weigel, Andreas, Weindl, Matthew, Weiss, Jan, Weldert, Chris, Wendt, Johannes, Werthebach, Mark, Weyrauch, Nathan, Whitehorn, Wiebusch, C. H., Dawn, Williams, Martin, Wolf, Kurt, Woschnagg, Gerrit, Wrede, Johan, Wulff, Xianwu, Xu, Yiqian, Xu, Juan Pablo Yanez, Yoshida, S., Shiqi, Yu, Tianlu, Yuan, Zelong, Zhang, Weidong, Jin, Hassan, Abdalla, Felix, Aharonian, Faical, Ait-Benkhali, Oguzhan, Anguener, Cornelia, Arcaro, Celine, Armand, Tom, Armstrong, Halim, Ashkar, Michael, Backes, Vardan, Baghmanyan, Victor Barbosa Martins, Anna, Barnacka, Monica, Barnard, Rowan, Batzofin, Yvonne, Becherini, David, Berge, Konrad, Bernlöhr, Baiyang, Bi, Markus, Boettcher, Catherine, Boisson, Julien, Bolmont, Mathieu de Bony, Mischa, Breuhaus, Robert, Brose, Francois, Brun, Tomasz, Bulik, Thomas, Bylund, Floriane, Cangemi, Sami, Caroff, Sabrina, Casanova, Jaqueline, Catalano, Pauline, Chambery, Tej Bahadur Chand, Andrew, Chen, Garret, Cotter, Malgorzata, Curlo, Jean Damascene Mbarubucyeye, Isak Delberth Davids, James, Davies, Justine, Devin, Arache, Djannati-Ataï, Anton, Dmytriiev, Axel, Donath, Victor, Doroshenko, Lente, Dreyer, Louis Du Plessis, Connor, Duffy, Kathrin, Egberts, Sabrina, Einecke, Gabriel, Emery, Jean-Pierre, Ernenwein, Steven, Fegan, Kirsty, Feijen, Armand, Fiasson, Gaëtan Fichet de Clairfontaine, Gerard, Fontaine, Lott, Frans, Matthias, Fuessling, Stefan, Funk, Stefano, Gabici, Yves, Gallant, Shahede, Ghafourizade, Gianluca, Giavitto, Luca, Giunti, Dorit, Glawion, Jean-Francois, Glicenstein, Marie-H('(e))l(`(e))ne, Grondin, Sumari, Hattingh, Maria, Haupt, German, Hermann, Jim, Hinton, Werner, Hofmann, Clemens, Hoischen, Tim, Holch, Markus, Holler, Dieter, Horns, Zhiqiu, Huang, David, Huber, Mario, Hörbe, Marek, Jamrozy, Felix, Jankowsky, Vikas, Joshi, Ira, Jung, Eli, Kasai, Krzysztof, Katarzynski, Ul(`(i)), Katz, Dmitry, Khangulyan, Bruno, Khelifi, Stefan, Klepser, Wlodek, Kluzniak, Nukri, Komin, Ruslan, Konno, Karl, Kosack, Dmitriy, Kostunin, Michael, Kreter, Ga( (s))per Kukec Mezek, Anu, Kundu, Giovanni, Lamanna, S('(e))bastien Le Stum, Anne, Lemiere, Marianne, Lemoine-Goumard, Jean-Philippe, Lenain, Fabian, Leuschner, Christelle, Levy, Thomas, Lohse, Anna, Luashvili, Iryna, Lypova, Jonathan, Mackey, Jhilik, Majumdar, Denys, Malyshev, Dmitry, Malyshev, Vincent, Marandon, Paolo, Marchegiani, Alexandre, Marcowith, Arnaud, Mares, Guillem Marti( extquotesingle)i-Devesa, Ramin, Marx, Gilles, Maurin, Pieter, Meintjes, Manuel, Meyer, Alison, Mitchell, Rafal, Moderski, Lars, Mohrmann, Alessandro, Montanari, Chris, Moore, Paul, Morris, Emmanuel, Moulin, Jacques, Muller, Thomas, Murach, Kaori, Nakashima, Mathieu Naurois (de), Amid, Nayerhoda, Hambeleleni, Ndiyavala, Jacek, Niemiec, Angel, Noel, Paul O( extquotesingle)Brien, Laenita Lorraine Oberholzer, Stefan, Ohm, Laura, Olivera-Nieto, Emma Ona-Wilhelmi (de), Michal, Ostrowski, Sebastian, Panny, Michael, Panter, Dan, Parsons, Giada, Peron, Santiago, Pita, Vincent, Poireau, Dmitry, Prokhorov, Heike, Prokoph, Gerd, Puehlhofer, Michael, Punch, Andreas, Quirrenbach, Patrick, Reichherzer, Anita, Reimer, Olaf, Reimer, Quentin, Remy, Matthieu, Renaud, Brian, Reville, Frank, Rieger, Carlo, Romoli, Gavin, Rowell, Bronislaw, Rudak, Hector Rueda Ricarte, Edna Ruiz Velasco, Vardan, Sahakian, Simon, Sailer, Heiko, Salzmann, David, Sanchez, Andrea, Santangelo, Manami, Sasaki, Johannes, Schaefer, Hester, Schutte, Ullrich, Schwanke, Fabian, Schüssler, Mohanraj, Senniappan, Albert, Seyffert, Shapopi, Jimmy N. S., Kleopas, Shiningayamwe, Rachel, Simoni, Atreyee, Sinha, Helene, Sol, Hugh, Spackman, Andreas, Specovius, Samuel Timothy Spencer, Marion, Spir-Jacob, Lukasz, Stawarz, Riaan, Steenkamp, Christian, Stegmann, Simon, Steinmassl, Constantin, Steppa, Lei, Sun, Tadayuki, Takahashi, Takaaki, Tanaka, Thomas, Tavernier, Andrew, Taylor, Regis, Terrier, Hannes, Thiersen, Charles, Thorpe-Morgan, Martin, Tluczykont, Lenka, Tomankova, Michelle, Tsirou, Naomi, Tsuji, Richard, Tuffs, Yasunobu, Uchiyama, Johann van der Walt, Christopher van Eldik, Carlo van Rensburg, Brian van Soelen, George, Vasileiadis, Johannes, Veh, Christo, Venter, Pascal, Vincent, Jacco, Vink, Völk, Heinrich J., Stefan, Wagner, Jason John Watson, Felix, Werner, Richard, White, Alicja, Wierzcholska, Yu Wun Wong, Hend, Yassin, Anke, Yusafzai, Michael, Zacharias, Roberta, Zanin, Davit, Zargaryan, Andrzej, Zdziarski, Andreas, Zech, Sylvia, Zhu, Andreas, Zmija, Samuel, Zouari, Natalia, Zywucka, The FACT Collaboration, The H.E.S.S. Collaboration, The IceCube Collaboration, The MAGIC Collaboration, The VERITAS Collaboration, and Współautorami artykułu są członkowie Magic Collaboration, IceCube Collaboration, FACT Collaboration, H.E.S.S. Collaboration, VERITAS Collaboration w liczbie 808

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Point source, Astrophysics::High Energy Astrophysical Phenomena, Gamma ray, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, IACT, Astrophysics, law.invention, High Energy Physics - Experiment, Telescope, High Energy Physics - Experiment (hep-ex), law, HESS - Abteilung Hinton, ddc:530, High Energy Physics::Experiment, MAGIC (telescope), Neutrino, Blazar, Astrophysics - High Energy Astrophysical Phenomena, Cherenkov radiation
Abstract

The realtime follow-up of neutrino events is a promising approach to search for astrophysical neutrino sources. It has so far provided compelling evidence for a neutrino point source: the flaring gamma-ray blazar TXS 0506+056 observed in coincidence with the high-energy neutrino IceCube-170922A detected by IceCube. The detection of very-high-energy gamma rays (VHE, $\mathrm{E} > 100\,\mathrm{GeV}$) from this source helped establish the coincidence and constrained the modeling of the blazar emission at the time of the IceCube event. The four major imaging atmospheric Cherenkov telescope arrays (IACTs) - FACT, H.E.S.S., MAGIC, and VERITAS - operate an active follow-up program of target-of-opportunity observations of neutrino alerts sent by IceCube. This program has two main components. One are the observations of known gamma-ray sources around which a cluster of candidate neutrino events has been identified by IceCube (Gamma-ray Follow-Up, GFU). Second one is the follow-up of single high-energy neutrino candidate events of potential astrophysical origin such as IceCube-170922A. GFU has been recently upgraded by IceCube in collaboration with the IACT groups. We present here recent results from the IACT follow-up programs of IceCube neutrino alerts and a description of the upgraded IceCube GFU system., Presented at the 37th International Cosmic Ray Conference (ICRC 2021). See arXiv:2107.06966 for all IceCube contributions. See arXiv:2108.05257 for all H.E.S.S. contributions

Published
2022

5. FACT - Database-based Analysis and Spectrum Calculations

Author

Laura Eisenberger, Alison Mitchell, Adelina Kalenski, Adrian Biland, Roland Walter, Dominik Baack, Roman Iotov, Maximilian Noethe, Dominik Neise, Daniela Dorner, Dorothee Hildebrand, Jens Buss, Dominik Elsaesser, Thomas Bretz, Vitalii Sliusar, Wolfgang Rhode, Karl Mannheim, Axel Arbet-Engels, Aleksander Paravac, Matteo Balbo, and Bernd Schleicher

Subjects
Database, Computer science, business.industry, Event (computing), Photodetector, computer.software_genre, law.invention, Telescope, Software, Duty cycle, law, Observatory, Latency (engineering), business, computer, Cherenkov radiation
Abstract

The First G-APD Cherenkov Telescope (FACT) is located at the Observatory Roque de los Muchachos on the Canary island La Palma. It uses the imaging air Cherenkov technique to detect gamma rays. With the help of silicon based photosensors in the camera, FACT is an ideal instrument to monitor a small sample of sources with a good time coverage. The automatic operation of the telescope allows an increase of the duty cycle of the instrument. An SQL database is part of the automatic analysis chain, where data on an event basis are stored. This way of storing the data has a several advantages. It can provide easy web-access to all data with no need of creating different user accounts for the analysers and without using special software. The data selection is done via simple queries to the database. This allows very flexible and powerful queries with, for example, user-defined time binning or background suppression. By using observed and simulated events, the complete analysis chain can be done, including the calculation of the measured energy spectrum. This could also be implemented to the Quick-Look Analysis to provide spectral information during the night with a low latency., PoS: Proceedings of Science, 395, ISSN:1824-8039, 37th International Cosmic Ray Conference (ICRC 2021)

Published
2022
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6. Periodicity Analysis of Mrk 501 and Mrk 421 in Gamma Rays

Author

Dominik Neise, Torsten Enßlin, Axel Arbet-Engels, Volodymyr Marchenko, Adrian Biland, Adelina Kalenski, Thomas Bretz, Bernd Schleicher, Laura Eisenberger, Dominik Elsaesser, Matteo Balbo, Daniela Dorner, Wolfgang Rhode, Phillip Arras, Roland Walter, Vincent Eberle, Fabian Theissen, Vitalii Sliusar, Karl Mannheim, Natalia Zywucka, Alison Mitchell, Andrija Kostić, Dorothee Hildebrand, Aleksander Paravac, Mariusz Tarnopolski, Michael Kreter, Manuel Boettcher, Dominik Baack, Roman Iotov, Maximilian Noethe, and Jens Buss

Subjects
Physics, Active galactic nucleus, Astrophysics::High Energy Astrophysical Phenomena, Gamma ray, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Light curve, law.invention, Telescope, Binary black hole, law, Quasiperiodic function, Blazar, Cherenkov radiation, Astrophysics::Galaxy Astrophysics
Abstract

Blazars, a subclass of active galactic nuclei (AGNs), are highly variable objects. Quasiperiodic oscillations (QPOs), which might originate from a binary black hole located at the AGN core,have been found in some blazar light curves. For the blazars Mrk 421 and Mrk 501, we test the possible QPO behavior using a variety of methods (generalized Lomb-Scargle periodogram,continuous-time autoregressive moving average models, wavelet scalograms, and A−T plane), studying systematic effects in detail. We use gamma-ray light curves from FACT, a ground-based imaging air Cherenkov telescope. We report herein on a 3 sigma significant QPO in Mrk 421., PoS: Proceedings of Science, 395, ISSN:1824-8039, 37th International Cosmic Ray Conference (ICRC 2021)

Published
2022

7. FACT - Highlights from more than Eight Years of Unbiased TeV Monitoring

Author

Adelina Kalenski, Aleksander Paravac, Thomas Bretz, Matteo Balbo, Adrian Biland, Bernd Schleicher, Dominik Elsaesser, Roland Walter, Alison Mitchell, Daniela Dorner, Dorothee Hildebrand, Laura Eisenberger, Karl Mannheim, Jens Buss, Wolfgang Rhode, Dominik Baack, Roman Iotov, Maximilian Noethe, Axel Arbet-Engels, Dominik Neise, and Vitalii Sliusar

Subjects
Telescope, Duty cycle, law, Spectral density, Astronomy, Context (language use), MAGIC (telescope), Blazar, Light curve, Cherenkov radiation, law.invention
Abstract

The First G-APD Cherenkov Telescope (FACT) has been monitoring blazars at TeV energies for more than eight years. Using solid state photo sensors and performing robotic operations results in a maximized duty cycle of the instrument and minimized observational gaps, providing an unprecedented data sample of more than 14700~hours of physics data. With an unbiased observing strategy, a small sample of sources is monitored. Results of an automatic quick-look analysis are published with low latency on an open-access website. Since 2014, close to 150 alerts including 11 astronomer's telegrams have been issued triggering target-of-opportunity observations and a variety of multi-wavelength studies. In 2016, FACT alerted MAGIC to a high state of 1ES 2344+51.4. The combined observations revealed a renewed extreme behaviour of the source. Thanks to target-of-opportunity observations and preplanned campaigns, several rich datasets with combined observations with INTEGRAL, XMM-Newton and AstroSAT are available for Mrk 421. Furthermore, dedicated campaigns each observing season provide multi-wavelength light curves and spectral energy distributions for the brightest blazars. The unprecedented, unbiased TeV data sample also provides the unique chance to study the duty cycle and the long-term spectral and temporal behaviour of the sources, including the search for periodic signals. Studying the long-term variability of Mrk 421 and Mrk 501 in the multi-wavelength context, correlations of different wavelengths are investigated searching for delays. In this presentation, selected highlights from more than eights years of monitoring will be summarized, including results from deep multi-instrument campaigns and long-term studies., PoS: Proceedings of Science, 395, ISSN:1824-8039, 37th International Cosmic Ray Conference (ICRC 2021)

Published
2022
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8. Studying the long-term spectral and temporal evolution of 1ES 1959$\mathplus$650

Author

Shunsuke, Sakurai, Acciari, Victor A., Stefano, Ansoldi, Lucio Angelo Antonelli, Axel Arbet Engels, Manuel, Artero, Katsuaki, Asano, Dominik, Baack, Ana, Babi('(c)), Andr('(e))s, Baquero, Ulisses Barres de Almeida, Juan Abel Barrio, Ivana, Batkovi('(c)), Josefa Becerra Gonz('(a))lez, Wlodek, Bednarek, Lorenzo, Bellizzi, Elisa, Bernardini, Maria-Isabel, Bernardos, Alessio, Berti, Jürgen, Besenrieder, Wrijupan, Bhattacharyya, Ciro, Bigongiari, Adrian, Biland, Oscar, Blanch, Hendrik, Bökenkamp, Giacomo Bonnoli, ( (Z))eljka Bo( (s))njak, Giovanni, Busetto, Roberto, Carosi, Giovanni, Ceribella, Matteo, Cerruti, Yating, Chai, Ashot, Chilingarian, Stefan, Cikota, Sidika Merve Colak, Eduardo, Colombo, Jose Luis Contreras, Juan, Cortina, Stefano, Covino, Giacomo D( extquotesingle)Amico, Valerio D( extquotesingle)Elia, Paolo Da Vela, Francesco, Dazzi, Alessandro De Angelis, Barbara De Lotto, Manuel, Delfino, Jordi, Delgado, Carlos Delgado Mendez, Davide, Depaoli, Federico Di Pierro, Leonardo Di Venere, Elia Do Souto Espi(~(n))eira, Dijana Dominis Prester, Alice, Donini, Daniela, Dorner, Michele, Doro, Dominik, Elsaesser, Vandad Fallah Ramazani, Alicia, Fattorini, Maria Victoria Fonseca, Lluis, Font, Christian, Fruck, Satoshi, Fukami, Yasushi, Fukazawa, Garc('(i))a L('(o))pez, Ramon J., Markus, Garczarczyk, Sargis, Gasparyan, Markus, Gaug, Giglietto, Nicola, Francesco, Giordano, Pawel, Gliwny, Nikola, Godinovi('(c)), David, Green, Jarred Gershon Green, Daniela, Hadasch, Alexander, Hahn, Lea, Heckmann, Javier, Herrera, John, Hoang, Dario, Hrupec, Moritz, Hütten, Tomohiro, Inada, Kazuma, Ishio, Yuki, Iwamura, Irene Jim('(e))nez Mart('(i))nez, Jenni, Jormanainen, L('(e))a, Jouvin, Marie, Karjalainen, Daniel, Kerszberg, Yukiho, Kobayashi, Hidetoshi, Kubo, Junko, Kushida, Alessandra, Lamastra, Damir, Lelas, Francesco, Leone, Elina, Lindfors, Lena, Linhoff, Saverio, Lombardi, Francesco, Longo, Rub('(e))n, L('(o))pez-Coto, Marcos, L('(o))pez-Moya, Alicia, L('(o))pez-Oramas, Loporchio, Serena, Bernardo Machado de Oliveira Fraga, Camilla, Maggio, Pratik, Majumdar, Martin, Makariev, Manuela, Mallamaci, Galina, Maneva, Marina, Manganaro, Karl, Mannheim, Laura, Maraschi, Mos(`(e)), Mariotti, Manel, Mart('(i))nez, Daniel, Mazin, Stefano, Menchiari, Simone, Mender, Sa( (s))a Mi('(c))anovi('(c)), Davide, Miceli, Tjark, Miener, Jose Miguel Miranda, Razmik, Mirzoyan, Edgar, Molina, Abelardo, Moralejo, Daniel, Morcuende, Victoria, Moreno, Elena, Moretti, Takeshi, Nakamori, Lara, Nava, Vitaly, Neustroev, Cosimo, Nigro, Kari, Nilsson, Kyoshi, Nishijima, Koji, Noda, Seiya, Nozaki, Yoshiki, Ohtani, Tomohiko, Oka, Jorge, Otero-Santos, Simona, Paiano, Michele, Palatiello, David, Paneque, Riccardo, Paoletti, Paredes, Josep M., Lovro, Pavleti('(c)), Pablo, Pe(~(n))il, Massimo, Persic, Marine, Pihet, Pier Giorgio Prada Moroni, Elisa, Prandini, Chaitanya, Priyadarshi, Ivica, Puljak, Wolfgang, Rhode, Marc, Rib('(o)), Javier, Rico, Chiara, Righi, Andrea, Rugliancich, Narek, Sahakyan, Takayuki, Saito, Konstancja, Satalecka, Francesco Gabriele Saturni, Bernd, Schleicher, Kevin, Schmidt, Thomas, Schweizer, Julian, Sitarek, Iva, ( (S))nidari('(c)), Dorota, Sobczy('(n))ska, Alessia, Spolon, Antonio, Stamerra, Jelena Stri( (s))kovi('(c)), Derek, Strom, Marcel, Strzys, Yusuke, Suda, Tihomir, Suri('(c)), Mitsunari, Takahashi, Ryuji, Takeishi, Fabrizio, Tavecchio, Petar, Temnikov, Tomislav, Terzi('(c)), Masahiro, Teshima, Luca, Tosti, Stefano, Truzzi, Antonio, Tutone, Santiago, Ubach, Juliane van Scherpenberg, Gaia, Vanzo, Monica VAZQUEZ ACOSTA, Sofia, Ventura, Vassil, Verguilov, Carlo Francesco Vigorito, Vincenzo, Vitale, Ievgen, Vovk, Martin, Will, Carolin, Wunderlich, Tokonatsu, Yamamoto, Darko, Zari('(c)), Matteo, Balbo, Thomas, Bretz, Jens, Buss, Laura, Eisenberger, Dorothee, Hildebrand, Roman, Iotov, Adelina, Kalenski, Alison, Mitchell, Dominik, Neise, Maximilian, Noethe, Aleksander, Paravac, Vitalii, Sliusar, Roland, Walter, Pietro, Grespan, Mari, Takahashi, Yasuyuki, Nabatame, and And

Published
2021

9. Multiwavelength variability and correlation studies of Mrk421 during historically low X-ray and $\upgamma$-ray activity in 2015{\textendash}2016

Author

Biswajit, Banerjee, Acciari, Victor A., Stefano, Ansoldi, Lucio Angelo Antonelli, Axel Arbet Engels, Manuel, Artero, Katsuaki, Asano, Dominik, Baack, Ana, Babi('(c)), Andr('(e))s, Baquero, Ulisses Barres de Almeida, Juan Abel Barrio, Ivana, Batkovi('(c)), Josefa Becerra Gonz('(a))lez, Wlodek, Bednarek, Lorenzo, Bellizzi, Elisa, Bernardini, Maria-Isabel, Bernardos, Alessio, Berti, Jürgen, Besenrieder, Wrijupan, Bhattacharyya, Ciro, Bigongiari, Adrian, Biland, Oscar, Blanch, Hendrik, Bökenkamp, Giacomo Bonnoli, ( (Z))eljka Bo( (s))njak, Giovanni, Busetto, Roberto, Carosi, Giovanni, Ceribella, Matteo, Cerruti, Yating, Chai, Ashot, Chilingarian, Stefan, Cikota, Sidika Merve Colak, Eduardo, Colombo, Jose Luis Contreras, Juan, Cortina, Stefano, Covino, Giacomo D( extquotesingle)Amico, Valerio D( extquotesingle)Elia, Paolo Da Vela, Francesco, Dazzi, Alessandro De Angelis, Barbara De Lotto, Manuel, Delfino, Jordi, Delgado, Carlos Delgado Mendez, Davide, Depaoli, Federico Di Pierro, Leonardo Di Venere, Elia Do Souto Espi(~(n))eira, Dijana Dominis Prester, Alice, Donini, Daniela, Dorner, Michele, Doro, Dominik, Elsaesser, Vandad Fallah Ramazani, Alicia, Fattorini, Maria Victoria Fonseca, Lluis, Font, Christian, Fruck, Satoshi, Fukami, Yasushi, Fukazawa, Garc('(i))a L('(o))pez, Ramon J., Markus, Garczarczyk, Sargis, Gasparyan, Markus, Gaug, Giglietto, Nicola, Francesco, Giordano, Pawel, Gliwny, Nikola, Godinovi('(c)), David, Green, Jarred Gershon Green, Daniela, Hadasch, Alexander, Hahn, Lea, Heckmann, Javier, Herrera, John, Hoang, Dario, Hrupec, Moritz, Hütten, Tomohiro, Inada, Kazuma, Ishio, Yuki, Iwamura, Irene Jim('(e))nez Mart('(i))nez, Jenni, Jormanainen, L('(e))a, Jouvin, Marie, Karjalainen, Daniel, Kerszberg, Yukiho, Kobayashi, Hidetoshi, Kubo, Junko, Kushida, Alessandra, Lamastra, Damir, Lelas, Francesco, Leone, Elina, Lindfors, Lena, Linhoff, Saverio, Lombardi, Francesco, Longo, Rub('(e))n, L('(o))pez-Coto, Marcos, L('(o))pez-Moya, Alicia, L('(o))pez-Oramas, Loporchio, Serena, Bernardo Machado de Oliveira Fraga, Camilla, Maggio, Pratik, Majumdar, Martin, Makariev, Manuela, Mallamaci, Galina, Maneva, Marina, Manganaro, Karl, Mannheim, Laura, Maraschi, Mos(`(e)), Mariotti, Manel, Mart('(i))nez, Daniel, Mazin, Stefano, Menchiari, Simone, Mender, Sa( (s))a Mi('(c))anovi('(c)), Davide, Miceli, Tjark, Miener, Jose Miguel Miranda, Razmik, Mirzoyan, Edgar, Molina, Abelardo, Moralejo, Daniel, Morcuende, Victoria, Moreno, Elena, Moretti, Takeshi, Nakamori, Lara, Nava, Vitaly, Neustroev, Cosimo, Nigro, Kari, Nilsson, Kyoshi, Nishijima, Koji, Noda, Seiya, Nozaki, Yoshiki, Ohtani, Tomohiko, Oka, Jorge, Otero-Santos, Simona, Paiano, Michele, Palatiello, David, Paneque, Riccardo, Paoletti, Paredes, Josep M., Lovro, Pavleti('(c)), Pablo, Pe(~(n))il, Massimo, Persic, Marine, Pihet, Pier Giorgio Prada Moroni, Elisa, Prandini, Chaitanya, Priyadarshi, Ivica, Puljak, Wolfgang, Rhode, Marc, Rib('(o)), Javier, Rico, Chiara, Righi, Andrea, Rugliancich, Narek, Sahakyan, Takayuki, Saito, Shunsuke, Sakurai, Konstancja, Satalecka, Francesco Gabriele Saturni, Bernd, Schleicher, Kevin, Schmidt, Thomas, Schweizer, Julian, Sitarek, Iva, ( (S))nidari('(c)), Dorota, Sobczy('(n))ska, Alessia, Spolon, Antonio, Stamerra, Jelena Stri( (s))kovi('(c)), Derek, Strom, Marcel, Strzys, Yusuke, Suda, Tihomir, Suri('(c)), Mitsunari, Takahashi, Ryuji, Takeishi, Fabrizio, Tavecchio, Petar, Temnikov, Tomislav, Terzi('(c)), Masahiro, Teshima, Luca, Tosti, Stefano, Truzzi, Antonio, Tutone, Santiago, Ubach, Juliane van Scherpenberg, Gaia, Vanzo, Monica VAZQUEZ ACOSTA, Sofia, Ventura, Vassil, Verguilov, Carlo Francesco Vigorito, Vincenzo, Vitale, Ievgen, Vovk, Martin, Will, Carolin, Wunderlich, Tokonatsu, Yamamoto, Darko, Zari('(c)), Matteo, Balbo, Thomas, Bretz, Jens, Buss, Laura, Eisenberger, Dorothee, Hildebrand, Roman, Iotov, Adelina, Kalenski, Alison, Mitchell, Dominik, Neise, Maximilian, Noethe, Aleksander, Paravac, Vitalii, Sliusar, Roland, Walter, Valverde, J., Horan, D., Giroletti, M., Perri, M., Verrecchia, F., Leto, C., Sadun, A. C., Moody, J. W., Joner, M., Marscher, A. P., Jorstad, S. G., Lähteenmäki, A., ( extasciitilde)Tornikoski, M., Ramakrishnan, V., Järvelä, E., Vera, R. J. C., Righini, S., Lien, A. Y., and And

Published
2021

10. 5.5 years multi-wavelength variability of Mrk 421: evidences of leptonic emission from the radio to TeV

Author

Adrian Biland, Dominik Baack, Roman Iotov, Marvin Beck, Maximilian Noethe, Thomas Bretz, Daniela Dorner, Jens Buss, Michael Blank, Karl Mannheim, Axel Arbet-Engels, Wolfgang Rhode, Amit Shukla, Bernd Schleicher, Matteo Balbo, Vitalii Sliusar, Dominik Elsaesser, Dominik Neise, Manuel Doerr, M. Bulinski, Dorothee Hildebrand, Aleksander Paravac, K. Sedlaczek, K. Bruegge, Laurits Tani, Marc Klinger, Fabian Theissen, and Roland Walter

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, High Energy Physics::Experiment, Multi wavelength, Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract

Mrk 421 is a high-synchrotron-peaked blazar featuring bright and persistent GeV and TeV emission. We use the longest and densest ongoing unbiased observing campaign obtained at TeV and GeV energies during 5.5 years with the FACT telescope and the Fermi-LAT detector. The contemporaneous multi-wavelength observations were used to characterize the variability of the source and to constrain the underlying physical mechanisms. We study and correlate light curves obtained by nine different instruments from radio to gamma rays and found two significant results. The TeV and X-ray light curves are very well correlated with lag, if any, shorter than a day. The GeV light curve varies independently and accurately leads the variations observed at long wavelengths, in particular in the radio band. We find that the observations match the predictions of leptonic models and suggest that the physical conditions vary along the jet, when the emitting region moves outwards., PoS: Proceedings of Science, 354, ISSN:1824-8039, Proceedings of High Energy Phenomena in Relativistic Outflows VII PoS (HEPRO VII9)

Published
2020
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11. Long-term multi-band photometric monitoring of Mrk 501

Author

Bernd Schleicher, Adrian Biland, Dorothee Hildebrand, Dominik Elsaesser, Jens Buss, Daniela Dorner, Laura Eisenberger, Alison Mitchell, Adelina Kalenski, Axel Arbet-Engels, Karl Mannheim, Matteo Balbo, Aleksander Paravac, Dominik Baack, Roland Walter, Roman Iotov, Maximilian Noethe, Dominik Neise, Thomas Bretz, Wolfgang Rhode, and Vitalii Sliusar

Subjects
Photon, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, law.invention, Telescope, law, 0103 physical sciences, Blazar, 010303 astronomy & astrophysics, Cherenkov radiation, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Computer Science::Information Retrieval, Compton scattering, Astronomy and Astrophysics, Light curve, Astrophysics - Astrophysics of Galaxies, Synchrotron, 3. Good health, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Precession, High Energy Physics::Experiment, Astrophysics - High Energy Astrophysical Phenomena
Abstract

Radio-to-TeV observations of the bright nearby (z=0.034) blazar Markarian 501 (Mrk 501), performed from December 2012 to April 2018, are used to study the emission mechanisms in its relativistic jet. We examined the multi-wavelength variability and the correlations of the light curves obtained by eight different instruments, including the First G-APD Cherenkov Telescope (FACT), observing Mrk 501 in very high-energy (VHE) gamma-rays at TeV energies. We identified individual TeV and X-ray flares and found a sub-day lag between variability in these two bands. Simultaneous TeV and X-ray variations with almost zero lag are consistent with synchrotron self-Compton (SSC) emission, where TeV photons are produced through inverse Compton scattering. The characteristic time interval of 5-25 days between TeV flares is consistent with them being driven by Lense-Thirring precession., 10 pages, 11 figures, Astronomy and astrophysics pre-print. arXiv admin note: text overlap with arXiv:2101.10651

Published
2021
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12. Mirror position determination for the alignment of Cherenkov Telescopes

Author

Dominik Baack, Michael Blank, Sabrina Einecke, Sebastian Achim Mueller, Karl Mannheim, A. Dmytriiev, Daniela Dorner, Adrian Biland, Gareth Hughes, Matthias Bergmann, Lena Linhoff, R. Walter, Aleksander Paravac, D. Hildebrand, Julia Thaele, Felicitas Pauss, K. Bruegge, Jens Buss, Thomas Bretz, Wolfgang Rhode, Maximilian Noethe, Fabian Temme, Andrii Neronov, Dominik Neise, Christina Hempfling, M. Domke, J. Adam, Max Ludwig Ahnen, A. Shukla, and Matteo Balbo

Subjects
Point spread function, Nuclear and High Energy Physics, Facet (geometry), Mirror image, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Curved mirror, IACT, 01 natural sciences, law.invention, Telescope, Optics, law, 0103 physical sciences, Image sensor, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Instrumentation, Cherenkov radiation, Physics, 010308 nuclear & particles physics, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Computer Science::Computer Vision and Pattern Recognition, Astrophysics - Instrumentation and Methods for Astrophysics, business
Abstract

Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures to map the faint Cherenkov light emitted in extensive air showers onto their image sensors. Segmented reflectors fulfill these needs using mass produced and light weight mirror facets. However, as the overall image is the sum of the individual mirror facet images, alignment is important. Here we present a method to determine the mirror facet positions on a segmented reflector in a very direct way. Our method reconstructs the mirror facet positions from photographs and a laser distance meter measurement which goes from the center of the image sensor plane to the center of each mirror facet. We use our method to both align the mirror facet positions and to feed the measured positions into our IACT simulation. We demonstrate our implementation on the 4 m First Geiger-mode Avalanche Cherenkov Telescope (FACT)., 11 figures, small ray tracing performance simulation, and implementation demonstration

Published
2017
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13. FACT - Probing the Periodicity of Mrk 421 and Mrk 501

Author

Matteo Balbo, Dominik Elsaesser, Daniela Dorner, Axel Arbet-Engels, M. Bulinski, K. Sedlaczek, Adrian Biland, Amit Shukla, Aleksander Paravac, Roland Walter, Dorothee Hildebrand, Thomas Bretz, Andrii Neronov, Dominik Neise, Wolfgang Rhode, Elan von Willert, Sebastian Achim Mueller, Karl Mannheim, Vitalii Sliusar, Bernd Schleicher, Marc Klinger, Fabian Theissen, Laurits Tani, Michael Blank, Manuel Doerr, K. Bruegge, Marvin Beck, Dominik Baack, Roman Iotov, Maximilian Noethe, and Jens Buss

Subjects
Physics, Active galactic nucleus, Astrophysics::High Energy Astrophysical Phenomena, Gamma ray, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Light curve, Accretion (astrophysics), law.invention, Telescope, Crab Nebula, law, Blazar, Astrophysics::Galaxy Astrophysics, Fermi Gamma-ray Space Telescope
Abstract

Markarian 421 and Markarian 501 are Active Galactic Nuclei and two of the most prominent sources of very high energetic gamma rays. In contrast to the predominantly stable Crab Nebula, the two blazars have extremely variable gamma-ray fluxes. Those could be caused by erratic accretion flow instabilities, but also by processes leading to quasi periodic oscillations (QPOs). Recently, hints of such a QPO of Mrk 501 with a period of about 322 days have been observed with the Large Area Telescope on-board of the Fermi satellite at GeV energies featuring global and local significances of the signal above 99%. The First G-APD Cherenkov Telescope (FACT) has monitored a small sample of known TeV gamma-ray sources including Mrk 421 and Mrk 501 over the last seven years. Therefore, it is ideally suited for periodicity studies of Active Galactic Nuclei, as they require unbiased and continuous long-term observations. Based on measurements of the well-known gamma-ray flux originating from the Crab Nebula, corrections to the measured light curves are applied. In total, 2500~hours of data for each of the two blazars have been analysed using the Lomb-Scargle algorithm. The resulting periodogram of Mrk 501 shows a hint of QPO with a similar period as the one observed by Fermi/LAT., PoS: Proceedings of Science, 358, ISSN:1824-8039, Proceedings of 36th International Cosmic Ray Conference (ICRC 2019)

Published
2019
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14. Fractional Variability: a Tool to Study Blazar Variability

Author

Sergej Grischagin, Dominik Elsaesser, F. Schulz, Dorothee Hildebrand, Adrian Biland, M. Bulinski, Vitalii Sliusar, Aleksander Paravac, Thomas Bretz, Matteo Balbo, Bernd Schleicher, Lena Linhoff, Axel Arbet-Engels, Andrii Neronov, Dominik Neise, Roland Walter, Wolfgang Rhode, Elan von Willert, Sebastian Achim Mueller, K. Bruegge, Michael Blank, Manuel Doerr, K. Sedlaczek, Daniela Dorner, Amit Shukla, Karl Mannheim, Dominik Baack, Maximilian Noethe, Jens Buss, Balbo, Matteo, Dorner, Daniela, Neronov, Andrii, Sliusar, Vitalii, and Walter, Roland

Subjects
Complete data, Active galactic nucleus, lcsh:Astronomy, Electromagnetic spectrum, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics, Radiation, Blazar, 01 natural sciences, lcsh:QB1-991, 0103 physical sciences, Range (statistics), ddc:530, Variability, 010303 astronomy & astrophysics, Physics, Active galactic nuclei, 010308 nuclear & particles physics, Astronomy and Astrophysics, Light curve, Aktiver galaktischer Kern, Fractional variability, Blazars, Variabilität, ddc:520
Abstract

Active Galactic Nuclei emit radiation over the whole electromagnetic spectrum up to TeV energies. Blazars are one subtype with their jets pointing towards the observer. One of their typical features is extreme variability on timescales, from minutes to years. The fractional variability is an often used parameter for investigating the degree of variability of a light curve. Different detection methods and sensitivities of the instruments result in differently binned data and light curves with gaps. As they can influence the physics interpretation of the broadband variability, the effects of these differences on the fractional variability need to be studied. In this paper, we study the systematic effects of completeness in time coverage and the sampling rate. Using public data from instruments monitoring blazars in various energy ranges, we study the variability of the bright TeV blazars Mrk 421 and Mrk 501 over the electromagnetic spectrum, taking into account the systematic effects, and compare our findings with previous results. Especially in the TeV range, the fractional variability is higher than in previous studies, which can be explained by the much longer (seven years compared to few weeks) and more complete data sample., Galaxies, 7 (2)

Published
2019

15. Single Photon Extraction for FACT’s SiPMs allows for Novel IACT Event Representation

Author

J. Oberkirch, Anton Dmytriiev, Adrian Biland, Dominik Baack, L. Kortmann, Felicitas Pauss, Michael Blank, K. Bruegge, Max Mahlke, Aleksander Paravac, Sabrina Einecke, Lena Linhoff, Daniela Dorner, Matteo Balbo, Roland Walter, Amit Shukla, Julia Thaele, Tina Herbst, Andrii Neronov, Karl Mannheim, Dominik Neise, Sebastian Achim Mueller, Bernd Schleicher, Fabian Temme, F. Schulz, Dorothee Hildebrand, Dominik Elsaesser, Jens Buss, Thomas Bretz, Maximilian Noethe, Wolfgang Rhode, Vitalii Sliusar, Christina Hempfling, J. Adam, and Max Ludwig Ahnen

Subjects
Physics, Photomultiplier, Photon, Pixel, business.industry, Physics::Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, IACT, law.invention, Telescope, Optics, Silicon photomultiplier, Air shower, law, business, Cherenkov radiation
Abstract

Imaging Atmospheric Cherenkov Telescopes provide large gamma-ray collection areas > 10^4 m^2 and successfully probe the high energetic gamma-ray sky by observing extensive air showers during the night. The First G-APD Cherenkov Telescope (FACT) explores silicon based photoelectric converters (called G-APDs or SiPMs) which provide more observation time with strong moonlight, a more stable photon gain over years of observations, and mechanically simpler imaging cameras. So far, the signal extraction methods used for FACT originate from sensors with no intrinsic quantized responses like photomultiplier tubes. This standard signal extraction is successfully used for the long time monitoring of the gamma-ray flux of bright blazars. However, we now challenge our classic signal extraction and explore single photon extraction methods to take advantage of the highly stable and quantized single photon responses of FACT's SiPM sensors. Instead of having one main pulse with one arrival time and one photon equivalent extracted for each pixel, we extract the arrival times of all individual photons in a pixel’s time line which opens up a new dimension in time for representing extensive air showers with an IACT. In this contribution, we will introduce our novel IACT event representation which is a list of single photon arrival times for each pixel (Photon-Stream). We will discuss our single photon extractor, its performance and its limitations. We will present example events where we identify individual, single air shower Cherenkov photons in the pool of individual, single night sky background photons., PoS: Proceedings of Science, 301, ISSN:1824-8039, Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017)

Published
2018
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16. Higher Order Temperature Dependence of SiPM used in FACT

Author

Thomas Bretz, Michael Blank, Matteo Balbo, Anton Dmytriiev, F. Schulz, J. Oberkirch, L. Kortmann, Adrian Biland, Lena Linhoff, Felicitas Pauss, Wolfgang Rhode, Andrii Neronov, Dominik Neise, Sabrina Einecke, Jens Buss, Dorothee Hildebrand, Karl Mannheim, Christina Hempfling, Daniela Dorner, Vitalii Sliusar, J. Adam, Dominik Elsaesser, Max Ludwig Ahnen, Tina Herbst, Aleksander Paravac, Maximilian Noethe, Fabian Temme, Amit Shukla, Dominik Baack, Julia Thaele, Sebastian Achim Mueller, Bernd Schleicher, Max Mahlke, and K. Bruegge

Subjects
Physics, business.industry, Physics::Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Photodetector, Cosmic ray, IACT, law.invention, Telescope, Wavelength, Optics, Silicon photomultiplier, law, Calibration, business, Cherenkov radiation
Abstract

Solid state photosensors, usually called SiPM or G-APD, seem ideal devices to be used in Imaging Atmospheric Cherenkov Telescopes (IACT). Nevertheless, their temperature dependence poses questions about their suitability in the harsh environment intrinsic to the operation of IACTs. While detailed measurements in the laboratory are possible with some sample sensors, limited data about the performance and uniformity of large samples exist. The First G-APD Cherenkov Telescope (FACT) is pioneering the usage of SiPMs for IACTs. Its camera consists of 1440 SiPMs and it is operated since October 2011 each night when observation conditions permit. Using no temperature stabilization system for the sensors, their temperature is closely coupled to the outside temperature that can change by more than 20 ∘C. While the strong temperature dependence of the gain of the sensors was shown to be easily compensated by adapting the applied voltage, there could also be higher order temperature dependencies of parameters like optical cross-talk, after-pulsing and wavelength dependent photon-detection efficiency. While external calibration devices could be used, one would have to proof that these devices do not have their own temperature dependencies. Instead, we use the constant flux of high energetic cosmic ray particles as calibration device. Their measured flux can depend on variable absorption and scattering of Cherenkov light e.g. due to dust and clouds, as well as on seasonal variations of the atmosphere. Nevertheless, using data sets where the temperature drastically changed within short time periods, we show that temperature dependencies of FACT, including the SiPMs, are well under control., PoS: Proceedings of Science, 301, ISSN:1824-8039, Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017)

Published
2018
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17. FACT – Performance of the First Cherenkov Telescope Observing with SiPMs

Author

F. Schulz, Anton Dmytriiev, Karl Mannheim, Thomas Bretz, J. Oberkirch, Wolfgang Rhode, Adrian Biland, Max Mahlke, Lena Linhoff, Dominik Elsaesser, Sabrina Einecke, Sebastian Achim Mueller, Aleksander Paravac, Dominik Baack, Christina Hempfling, J. Adam, Max Ludwig Ahnen, K. Bruegge, Tina Herbst, Roland Walter, Michael Blank, Matteo Balbo, Daniela Dorner, Andrii Neronov, Dominik Neise, Felicitas Pauss, Bernd Schleicher, Vitalii Sliusar, Amit Shukla, Julia Thaele, Jens Buss, Fabian Temme, L. Kortmann, Maximilian Noethe, and Dorothee Hildebrand

Subjects
Physics, Physics::Instrumentation and Detectors, media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, Cosmic distance ladder, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Context (language use), First light, law.invention, Telescope, Crab Nebula, Sky, law, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Blazar, Cherenkov radiation, media_common
Abstract

The First G-APD Cherenkov Telescope (FACT) is pioneering the usage of silicon photo mul- tipliers (SiPMs also known as G-APDs) for the imaging atmospheric Cherenkov technique. It is located at the Observatorio Roque de los Muchachos on the Canary island of La Palma. Since first light in October 2011, it is monitoring bright TeV blazars in the northern sky. By now, FACT is the only imaging atmospheric Cherenkov telescope operating with S I PMs on a nightly basis. Over the course of the last five years, FACT has been demonstrating their reliability and excel- lent performance. Moreover, their robustness allowed for an increase of the duty cycle including nights with strong moon light without the need for UV-filters. In this contribution, we will present the performance of the first Cherenkov telescope using solid state photo sensors, which was determined in analysis of data from Crab Nebula, the so called standard candle in gamma-ray astronomy. The presented analysis chain utilizes modern data mining methods and unfolding techniques to obtain the energy spectrum of this source. The characteristical results of such an analysis will be reported providing, e. g., the angular and energy resolution of FACT, as well as, the energy spectrum of the Crab Nebula. Furthermore, these results are discussed in the context of the performance of coexisting Cherenkov telescopes., PoS: Proceedings of Science, 301, ISSN:1824-8039, Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017)

Published
2018
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18. Measuring the Optical Point Spread Function of FACT Using the Cherenkov Camera

Author

Max Mahlke, Fabian Temme, Daniela Dorner, J. Oberkirch, Max Ludwig Ahnen, Adrian Biland, Amit Shukla, Felicitas Pauss, Michael Blank, Vitalii Sliusar, Lena Linhoff, Aleksander Paravac, F. Schulz, Dominik Baack, Bernd Schleicher, L. Kortmann, Sebastian Achim Mueller, Anton Dmytriiev, Roland Walter, K. Bruegge, Christina Hempfling, J. Adam, Matteo Balbo, Thomas Bretz, Dorothee Hildebrand, Maximilian Noethe, Sabrina Einecke, Jens Buss, Julia Thaele, Wolfgang Rhode, Tina Herbst, Andrii Neronov, Dominik Neise, Dominik Elsaesser, and Karl Mannheim

Subjects
Physics, Point spread function, Pixel, business.industry, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Field of view, Reflector (antenna), IACT, law.invention, Radio telescope, Telescope, Optics, law, Astrophysics::Earth and Planetary Astrophysics, business, Cherenkov radiation
Abstract

FACT, the First G-APD Cherenkov Telescope, is an Imaging Air Cherenkov Telescope (IACT) operating since 2011 at the Observatorio del Roque de los Muchachos on the Canary Island of La Palma. As typical for IACTs, its reflector is comprised of smaller mirror facets and not protected by a dome. In the case of FACT, 30 hexagonal facets form a total mirror area of 9.5 m 2 . Hence, it is crucial to monitor the optical properties of this system and realign the facets if necessary. Up to now, measuring the Point Spread Function of FACT required human interaction to mount a screen and an optical camera. In this contribution, a new method to measure the optical Point Spread Function using directly the Cherenkov camera of the telescope is presented. Inspired by the method radio telescopes use to determine their resolution, the telescope is pointed towards a fixed position on the trajectory of a star. During the star’s passage through the field of view, the camera is read out using a fixed rate. In each event, the pedestal variance is determined for each pixel. This value is directly correlated with the amount of night sky background light a pixel received. Translating the time of the measurement to the position of the star in the camera enables to determine the optical point spread function from this measurement. As the measurement is done for each pixel along the trajectory of the star, the Point Spread Function can be determined not only for the camera center but for the entire field of view. In this contribution, the new method will also be compared with the existing methods of determining the optical Point Spread Function: direct measurement with an optical camera and the width of Muon ring events, PoS: Proceedings of Science, 301, ISSN:1824-8039

Published
2017
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19. First study of combined blazar light curves with FACT and HAWC

Author

Daniela Dorner, Sabrina Einecke, Julia Thaele, Amit Shukla, Felicitas Pauss, Michael Blank, Adrian Biland, Matthias Bergmann, Christina Hempfling, Thomas Bretz, J. Adam, Anton Dmytiiev, Max Ludwig Ahnen, Lena Linhoff, Matteo Balbo, Kai Brügge, Wolfgang Rhode, Aleksander Paravac, Dorothee Hildebrand, Sebastian Müller, Gareth Hughes, Roland Walter, R. J. Lauer, Karl Mannheim, Andrii Neronov, Dominik Neise, Dominik Baack, Maximilian Noethe, Jens Buss, and Fabian Temme

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Astrophysics::High Energy Astrophysical Phenomena, media_common.quotation_subject, Detector, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Light curve, law.invention, Telescope, Observatory, Sky, Duty cycle, law, Astrophysics - High Energy Astrophysical Phenomena, Blazar, Cherenkov radiation, Remote sensing, media_common
Abstract

For studying variable sources like blazars, it is crucial to achieve unbiased monitoring, either with dedicated telescopes in pointing mode or survey instruments. At TeV energies, the High Altitude Water Cherenkov (HAWC) observatory monitors approximately two thirds of the sky every day. It uses the water Cherenkov technique, which provides an excellent duty cycle independent of weather and season. The First G-APD Cherenkov Telescope (FACT) monitors a small sample of sources with better sensitivity, using the imaging air Cherenkov technique. Thanks to its camera with silicon-based photosensors, FACT features an excellent detector performance and stability and extends its observations to times with strong moonlight, increasing the duty cycle compared to other imaging air Cherenkov telescopes. As FACT and HAWC have overlapping energy ranges, a joint study can exploit the longer daily coverage given that the observatories' locations are offset by 5.3 hours. Furthermore, the better sensitivity of FACT adds a finer resolution of features on hour-long time scales, while the continuous duty cycle of HAWC ensures evenly sampled long-term coverage. Thus, the two instruments complement each other to provide a more complete picture of blazar variability. In this presentation, the first joint study of light curves from the two instruments will be shown, correlating long-term measurements with daily sampling between air and water Cherenkov telescopes. The presented results focus on the study of the variability of the bright blazars Mrk 421 and Mrk 501 during the last two years featuring various flaring activities., Comment: 6 pages, 2 figures. Contribution to the 6th International Symposium on High Energy Gamma-Ray Astronomy (Gamma2016), Heidelberg, Germany. To be published in the AIP Conference Proceedings

Published
2017
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20. FACT - First Energy Spectrum from a SiPM Cherenkov Telescope

Author

Thomas Bretz, A.-K. Overkemping, Wolfgang Rhode, Felicitas Pauss, Matthias Bergmann, G. Hughes, Matteo Balbo, Simona Toscano, Christina Hempfling, Adrian Biland, Dominik Neise, Aylin Wilbert, Werner Lustermann, Sebastian Achim Mueller, J. Freiwald, Julia Thaele, Patrick Vogler, Aleksander Paravac, Christian Bockermann, Karl Mannheim, Max Ludwig Ahnen, Dorothee Hildebrand, Roland Walter, Kai Brügge, K. Meier, Andrii Neronov, Daniela Dorner, Sabrina Einecke, Katharina Morik, Fabian Temme, Jens Buss, and Maximilian Noethe

Subjects
Telescope, Physics, Silicon photomultiplier, Cherenkov detector, law, Energy spectrum, Astronomy, Cherenkov radiation, law.invention
Abstract

The 34th International Cosmic Ray Conference : ICRC2015 : 30 July- 6 August, 2015, The Hague, The Netherlands / IUPAP The 34th International Cosmic Ray Conference, ICRC2015, The Hague, Netherlands, 30 Jul 2015 - 6 Aug 2015; Trieste, Italy : Sissa Medialab srl, Proceedings of science 236, 707 pp. (2016). doi:10.22323/1.236.0707, Published by Sissa Medialab srl, Trieste, Italy

Published
2016
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21. FACT -- Novel mirror alignment using Bokeh and enhancement of the VERITAS SCCAN alignment method

Author

Adrian Biland, Matthias Bergmann, Maximilian Noethe, Patrick Vogler, Fabian Temme, A.-K. Overkemping, Simona Toscano, Christina Hempfling, Werner Lustermann, Felicitas Pauss, Jens Buss, G. Hughes, Julia Thaele, Daniela Dorner, Andrii Neronov, Dominik Neise, Sebastian Achim Mueller, K. Meier, Matteo Balbo, Dorothee Hildebrand, Sabrina Einecke, Karl Mannheim, J. Freiwald, Max Ludwig Ahnen, Aylin Wilbert, Thomas Bretz, Aleksander Paravac, Wolfgang Rhode, and Roland Walter

Subjects
Physics, Beam diameter, Muon, Optics, Bokeh, business.industry, Resolution (electron density), Cosmic ray, Star (graph theory), business
Published
2016
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22. Bokeh mirror alignment for Cherenkov telescopes

Author

A. Shukla, Michael Blank, Dominik Neise, Dorothee Hildebrand, Sabrina Einecke, Jens Buss, Christina Hempfling, J. Adam, K. Bruegge, Max Ludwig Ahnen, Daniela Dorner, Andrii Neronov, Thomas Bretz, Fabian Temme, Wolfgang Rhode, Anton Dmytriiev, Matteo Balbo, Adrian Biland, Karl Mannheim, Aleksander Paravac, Julia Thaele, Lena Linhoff, Roland Walter, Dominik Baack, Maximilian Noethe, Matthias Bergmann, Felicitas Pauss, Sebastian Achim Mueller, and G. Hughes

Subjects
Physics, Measurement method, Reflector (photography), Bokeh, 010308 nuclear & particles physics, business.industry, IACT, Cherenkov Telescope Array, 01 natural sciences, Optics, 0103 physical sciences, business, 010303 astronomy & astrophysics, Cherenkov radiation
Abstract

Segmented imaging reflectors are a great choice for Imaging Atmospheric Cherenkov Telescopes (IACTs). However, the alignment of the individual mirror facets is challenging. We align a segmented reflector by observing and optimizing its Bokeh function. Bokeh alignment can already be done with very little resources and little preparation time. Further, Bokeh alignment can be done anytime, even during the day. We present a first usage of Bokeh alignment on FACT, a 4m IACT on Canary Island La Palma, Spain and further a first Bokeh alignment test on the CTA MST IACT prototype in Brelin Adlershof.

Published
2016
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23. Bokeh Mirror Alignment for Cherenkov Telescopes

Author

Julia Thaele, Patrick Vogler, Dominik Neise, Michael Blank, Felicitas Pauss, Matteo Balbo, Max Ludwig Ahnen, K. Bruegge, A. Shukla, Daniela Dorner, Matthias Bergmann, G. Hughes, Aylin Wilbert, Sebastian Achim Mueller, Adrian Biland, Dorothee Hildebrand, Christina Hempfling, M. Domke, Simona Toscano, Andrii Neronov, A.-K. Overkemping, Thomas Bretz, Wolfgang Rhode, Werner Lustermann, Roland Walter, Dominik Baack, Maximilian Noethe, Sabrina Einecke, Jens Buss, Karl Mannheim, Fabian Temme, and Aleksander Paravac

Subjects
Point spread function, Bokeh, Aperture, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, 01 natural sciences, law.invention, Telescope, Optics, law, 0103 physical sciences, Focal length, Image sensor, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Cherenkov radiation, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Computer Science::Computer Vision and Pattern Recognition, Focus (optics), business, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures and high image intensities to map the faint Cherenkov light emitted from cosmic ray air showers onto their image sensors. Segmented reflectors fulfill these needs, and composed from mass production mirror facets they are inexpensive and lightweight. However, as the overall image is a superposition of the individual facet images, alignment remains a challenge. Here we present a simple, yet extendable method, to align a segmented reflector using its Bokeh. Bokeh alignment does not need a star or good weather nights but can be done even during daytime. Bokeh alignment optimizes the facet orientations by comparing the segmented reflectors Bokeh to a predefined template. The optimal Bokeh template is highly constricted by the reflector's aperture and is easy accessible. The Bokeh is observed using the out of focus image of a near by point like light source in a distance of about 10 focal lengths. We introduce Bokeh alignment on segmented reflectors and demonstrate it on the First Geiger-mode Avalanche Cherenkov Telescope (FACT) on La Palma, Spain., Comment: accepted for publication in Astroparticle Physics

Published
2016
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24. FACT - Calibration of Imaging Atmospheric Cerenkov Telescopes with Muon Rings

Author

Adrian Biland, Wolfgang Rhode, A.-K. Overkemping, Jens Buss, Felicitas Pauss, Werner Lustermann, Christina Hempfling, Fabian Temme, Daniela Dorner, Aylin Wilbert, Aleksander Paravac, Max Ludwig Ahnen, Andrii Neronov, Dominik Neise, Sabrina Einecke, Karl Mannheim, Patrick Vogler, Matteo Balbo, Maximilian Noethe, Gareth Hughes, Sebastian Achim Mueller, Simona Toscano, Roland Walter, Christian Bockermann, J. Freiwald, Kai Brügge, K. Meier, Katharina Morik, Matthias Bergmann, Dorothee Hildebrand, Julia Thaele, and Thomas Bretz

Subjects
Nuclear physics, Physics, Muon, Calibration, Time resolution, Astrophysics
Abstract

The 34th International Cosmic Ray Conference : ICRC2015 : 30 July- 6 August, 2015, The Hague, The Netherlands / IUPAP The 34th International Cosmic Ray Conference, ICRC2015, The Hague, Netherlands, 30 Jul 2015 - 6 Aug 2015; Trieste, Italy : Sissa Medialab srl, Proceedings of science 236, 733 pp. (2016). doi:10.22323/1.236.0733, Published by Sissa Medialab srl, Trieste, Italy

Published
2016
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25. Normalized and Asynchronous Mirror Alignment for Cherenkov Telescopes

Author

Aylin Wilbert, A. Shukla, Werner Lustermann, Dominik Neise, Adrian Biland, Patrick Vogler, Jens Buss, G. Hughes, Andrii Neronov, Fabian Temme, K. Bruegge, Max Ludwig Ahnen, Simona Toscano, Sebastian Achim Mueller, Roland Walter, Karl Mannheim, A.-K. Overkemping, Matthias Bergmann, Michael Blank, Sabrina Einecke, Dominik Baack, Christina Hempfling, M. Domke, Maximilian Noethe, Thomas Bretz, Matteo Balbo, Daniela Dorner, Wolfgang Rhode, Felicitas Pauss, Dorothee Hildebrand, Aleksander Paravac, and Julia Thaele

Subjects
Point spread function, Facet (geometry), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Tracking (particle physics), 01 natural sciences, law.invention, Telescope, Optics, law, 0103 physical sciences, Image sensor, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Cherenkov radiation, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Beam diameter, 010308 nuclear & particles physics, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Reflection (physics), business, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures and high image intensities to map the faint Cherenkov light emitted from cosmic ray air showers onto their image sensors. Segmented reflectors fulfill these needs, and as they are composed from mass production mirror facets they are inexpensive and lightweight. However, as the overall image is a superposition of the individual facet images, alignment is a challenge. Here we present a computer vision based star tracking alignment method, which also works for limited or changing star light visibility. Our method normalizes the mirror facet reflection intensities to become independent of the reference star's intensity or the cloud coverage. Using two CCD cameras, our method records the mirror facet orientations asynchronously of the telescope drive system, and thus makes the method easy to integrate into existing telescopes. It can be combined with remote facet actuation, but does not require one to work. Furthermore, it can reconstruct all individual mirror facet point spread functions without moving any mirror. We present alignment results on the 4 meter First Geiger-mode Avalanche Cherenkov Telescope (FACT)., Comment: accepted for publication in Astroparticle Physics

Published
2016
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26. FACT - Influence of SiPM Crosstalk on the Performance of an Operating Cherenkov Telescope

Author

Katharina Morik, Andrii Neronov, Adrian Biland, Dorothee Hildebrand, Sabrina Einecke, Felicitas Pauss, Maximilian Noethe, Julia Thaele, Jens Buss, Simona Toscano, Roland Walter, Thomas Bretz, Kai Brügge, K. Meier, Daniela Dorner, Aleksander Paravac, Fabian Temme, Wolfgang Rhode, G. Hughes, Werner Lustermann, Dominik Neise, Patrick Vogler, Sebastian Achim Mueller, Christina Hempfling, Aylin Wilbert, Max Ludwig Ahnen, Matteo Balbo, A.-K. Overkemping, J. Freiwald, Christian Bockermann, and Karl Mannheim

Subjects
Crosstalk, Physics, Telescope, Silicon photomultiplier, Optics, business.industry, law, Optoelectronics, business, Cherenkov radiation, law.invention
Abstract

The 34th International Cosmic Ray Conference : ICRC2015 : 30 July- 6 August, 2015, The Hague, The Netherlands / IUPAP The 34th International Cosmic Ray Conference, ICRC2015, The Hague, Netherlands, 30 Jul 2015 - 6 Aug 2015; Trieste, Italy : Sissa Medialab srl, Proceedings of science 236, 863 pp. (2016). doi:10.22323/1.236.0863, Published by Sissa Medialab srl, Trieste, Italy

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27. FACT - TeV flare alerts triggering multi-wavelength observations

Author

A.-K. Overkemping, Simona Toscano, Adrian Biland, Werner Lustermann, Dominik Neise, Fabian Temme, Kai Brügge, K. Meier, Aylin Wilbert, Dorothee Hildebrand, Andrii Neronov, Daniela Dorner, Matteo Balbo, Felicitas Pauss, Maximilian Noethe, Sabrina Einecke, Jens Buss, Sebastian Achim Mueller, Karl Mannheim, G. Hughes, Aleksander Paravac, Julia Thaele, Max Ludwig Ahnen, J. Freiwald, Roland Walter, Matthias Bergmann, Thomas Bretz, Wolfgang Rhode, Patrick Vogler, and Christina Hempfling

Subjects
Physics, law, Gamma ray detectors, Astronomy, Multi wavelength, Flare, law.invention
Abstract

The 34th International Cosmic Ray Conference : ICRC2015 : 30 July- 6 August, 2015, The Hague, The Netherlands / IUPAP The 34th International Cosmic Ray Conference, ICRC2015, The Hague, Netherlands, 30 Jul 2015 - 6 Aug 2015; Trieste, Italy : Sissa Medialab srl, Proceedings of science 236, 704 pp. (2016). doi:10.22323/1.236.0704, Published by Sissa Medialab srl, Trieste, Italy

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