M. I. Martínez, V. Neustroev, Francesco Longo, Maria-Isabel Bernardos, Alessandro Marchini, Alicia Fattorini, Tomohiko Oka, Katsuaki Asano, U. Barres de Almeida, Damir Lelas, Adrian Biland, D. Hadasch, D. Miceli, Sanae Inoue, Giacomo D'Amico, Yating Chai, Stefan Cikota, Pawel Gliwny, I. Vovk, David A. Green, R. J. García López, Narek Sahakyan, Stefano Covino, Lea Heckmann, Francesco Gabriele Saturni, J. Becerra González, Armin Nabizadeh, F. D'Ammando, J. Rico, M. Vazquez Acosta, Nicola Giglietto, Alexander Hahn, Nikola Godinovic, Dorota Sobczyńska, G. Ferrara, G. Busetto, E. Molina, Satoshi Fukami, Shunsuke Sakurai, Jarred Gershon Green, Elisabetta Bissaldi, C. Perennes, D. Strom, Yusuke Suda, E. Colombo, Lab Saha, Alice Donini, Kazuma Ishio, Massimo Persic, L. A. Antonelli, Martin Makariev, Dominik Baack, P. G. Prada Moroni, J. Kushida, Ivica Puljak, Victor Moreno, Oscar Blanch, S. Ventura, C. Nigro, Carlo Vigorito, F. Leone, D. Dominis Prester, Alessandra Lamastra, J. A. Barrio, John Hoang, V. Verguilov, Tomoki Saito, J. M. Paredes, Antonio Stamerra, Giovanni Ceribella, Rodolfo Carosi, I. Jiménez, V. D'Elia, Pratik Majumdar, M. V. Fonseca, Daniel Morcuende, Jose Luis Contreras, Jenni Jormanainen, Vincenzo Vitale, T. Schweizer, A. Arbet Engels, S. Loporchio, A. Rugliancich, Marina Manganaro, A. De Angelis, M. Karjalainen, Sargis Gasparyan, Stefano Menchiari, Y. Kajiwara, Fabrizio Tavecchio, M. Palatiello, Manuela Mallamaci, Masahiro Teshima, S. Paiano, Luca Tosti, I. Snidaric, Mosè Mariotti, Martin Will, M. Orienti, S. Mićanović, Ashot Chilingarian, Wolfgang Rhode, Lluis Font, B. Machado de Oliveira Fraga, Tihomir Surić, Manuel Artero, Juan Cortina, Toshiaki Inada, Yuki Iwamura, Stefano Truzzi, D. Zarić, Saverio Lombardi, Francesco Dazzi, Simone Mender, E. Do Souto Espiñeira, Tomislav Terzić, Dario Hrupec, Pablo Peñil, Konstancja Satalecka, L. Maraschi, Giacomo Bonnoli, Sidika Merve Colak, Elina Lindfors, Marcos López-Moya, G. Maneva, Karl Mannheim, Wlodek Bednarek, L. Di Venere, Mitsunari Takahashi, Michele Doro, J. van Scherpenberg, Stefano Ansoldi, Daniel Mazin, Riccardo Paoletti, Christian Fruck, Ivana Batković, E. Prandini, Wrijupan Bhattacharyya, Julian Sitarek, Santiago Ubach, Y. Kobayashi, F. Di Pierro, Jürgen Besenrieder, Lorenzo Bellizzi, Francesco Giordano, Antonio Tutone, J. Otero-Santos, K. Nishijima, Jose Miguel Miranda, Kai Phillip Schmidt, A. Berti, Yoshiki Ohtani, Tjark Miener, David Paneque, D. Elsaesser, Jordi Delgado, Ž. Bošnjak, Matteo Cerruti, Chiara Righi, V. Fallah Ramazani, V. A. Acciari, P. Temnikov, P. Da Vela, Manuel Delfino, Lovro Pavletić, Moritz Hütten, Chaitanya Priyadarshi, Carolin Wunderlich, Ana Babić, C. Delgado Mendez, M. Strzys, Kari Nilsson, Camilla Maggio, Daniela Dorner, Gaia Vanzo, M. Gaug, J. Herrera, Koji Noda, Elisa Bernardini, Alessia Spolon, Léa Jouvin, A. López-Oramas, S. Cutini, Daniel Kerszberg, Marc Ribó, B. De Lotto, S. Nozaki, Andrés Baquero, Hidetoshi Kubo, Abelardo Moralejo, E. Moretti, D. Depaoli, Bernd Schleicher, M. Minev, R. Mirzoyan, Ciro Bigongiari, M. Garczarczyk, R. López-Coto, German Research Foundation, Swiss National Science Foundation, Ministerio de Ciencia, Innovación y Universidades (España), Department of Atomic Energy (India), Institute for Cosmic Ray Research (Japan), University of Tokyo, Japan Society for the Promotion of Science, Ministry of Education, Culture, Sports, Science and Technology (Japan), Ministry of Education and Research (Romania), Academy of Finland, La Caixa, Croatian Science Foundation, University of Rijeka, Polish National Agency for Academic Exchange, European Commission, Ministerio de Economía y Competitividad (España), Istituto Nazionale di Astrofisica, Acciari, Va, Ansoldi, S, Antonelli, La, Engels, Aa, Artero, M, Asano, K, Baack, D, Babic, A, Baquero, A, de Almeida, Ub, Barrio, Ja, Batkovic, I, Gonzalez, Jb, Bednarek, W, Bellizzi, L, Bernardini, E, Bernardos, M, Berti, A, Besenrieder, J, Bhattacharyya, W, Bigongiari, C, Biland, A, Blanch, O, Bosnjak, Z, Busetto, G, Carosi, R, Ceribell, G, Cerruti, M, Chai, Y, Chilingarian, A, Cikota, S, Colak, Sm, Colombo, E, Contreras, Jl, Cortina, J, Covino, S, D'Amico, G, D'Elia, V, Da Vela, P, Dazzi, F, De Angelis, A, De Lotto, B, Delfino, M, Delgado, J, Mendez, Cd, Depaoli, D, Di Pierro, F, Di Venere, L, Espineira, Ed, Prester, Dd, Donini, A, Dorner, D, Doro, M, Elsaesser, D, Ramazani, Vf, Fattorini, A, Ferrara, G, Fonseca, Mv, Font, L, Fruck, C, Fukami, S, Lopez, Rjg, Garczarczyk, M, Gasparyan, S, Gaug, M, Giglietto, N, Giordano, F, Gliwny, P, Godinovic, N, Green, Jg, Green, D, Hadasch, D, Hahn, A, Heckmann, L, Herrera, J, Hoang, J, Hrupec, D, Hutten, M, Inada, T, Inoue, S, Ishio, K, Iwamura, Y, Jimenez, I, Jormanainen, J, Jouvin, L, Kajiwara, Y, Karjalainen, M, Kerszberg, D, Kobayashi, Y, Kubo, H, Kushida, J, Lamastra, A, Lelas, D, Leone, F, Lindfors, E, Lombardi, S, Longo, F, Lopez-Coto, R, Lopez-Moya, M, Lopez-Oramas, A, Loporchio, S, Fraga, Bmd, Maggio, C, Majumdar, P, Makariev, M, Mallamaci, M, Maneva, G, Manganaro, M, Mannheim, K, Maraschi, L, Mariotti, M, Martinez, M, Mazin, D, Menchiari, S, Mender, S, Micanovic, S, Miceli, D, Miener, T, Minev, M, Miranda, Jm, Mirzoyan, R, Molina, E, Moralejo, A, Morcuende, D, Moreno, V, Moretti, E, Neustroev, V, Nigro, C, Nilsson, K, Nishijima, K, Noda, K, Nozaki, S, Ohtani, Y, Oka, T, Otero-Santos, J, Paiano, S, Palatiello, M, Paneque, D, Paoletti, R, Paredes, Jm, Pavletic, L, Penil, P, Perennes, C, Moroni, Pgp, Prandini, E, Priyadarshi, C, Puljak, I, Rhode, W, Ribo, M, Rico, J, Righi, C, Rugliancich, A, Saha, L, Sahakyan, N, Saito, T, Sakurai, S, Satalecka, K, Saturni, Fg, Schleicher, B, Schmidt, K, Schweizer, T, Sitarek, J, Snidaric, I, Sobczynska, D, Spolon, A, Stamerra, A, Strom, D, Strzys, M, Suda, Y, Suric, T, Takahashi, M, Tavecchio, F, Temnikov, P, Terzic, T, Teshima, M, Tosti, L, Truzzi, S, Tutone, A, Ubach, S, Vanscherpenberg, J, Vanzo, G, Acosta, Mv, Ventura, S, Verguilov, V, Vigorito, Cf, Vitale, V, Vovk, I, Will, M, Wunderlich, C, Zaric, D, Bissaldi, E, Bonnoli, G, Cutini, S, D'Ammando, F, Nabizadeh, A, Marchini, A, and Orienti, M
Full list of authors: Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels, A. ; Artero, M.; Asano, K.; Baack, D.; Babić, A.; Baquero, A.; Barres de Almeida, U.; Barrio, J. A.; Batković, I.; Becerra González, J.; Bednarek, W.; Bellizzi, L.; Bernardini, E.; Bernardos, M.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch, O.; Bošnjak, Ž.; Busetto, G.; Carosi, R.; Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.; Cikota, S.; Colak, S. M.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Amico, G.; D'Elia, V.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.; Delfino, M.; Delgado, J.; Delgado Mendez, C.; Depaoli, D.; Pierro, F. Di; Venere, L. Di; Do Souto Espiñeira, E.; Dominis Prester, D.; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Fallah Ramazani, V.; Fattorini, A.; Ferrara, G.; Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.; García López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović, N.; Green, J. G.; Green, D.; Hadasch, D.; Hahn, A.; Heckmann, L.; Herrera, J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada, T.; Inoue, S.; Ishio, K.; Iwamura, Y.; Jiménez, I.; Jormanainen, J.; Jouvin, L.; Kajiwara, Y.; Karjalainen, M.; Kerszberg, D.; Kobayashi, Y.; Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.; Lombardi, S.; Longo, F.; López-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio, S.; Machado de Oliveira Fraga, B.; Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menchiari, S.; Mender, S.; Mićanović, S.; Miceli, D.; Miener, T.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti, E.; Neustroev, V.; Nigro, C.; Nilsson, K.; Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.; Oka, T.; Otero-Santos, J.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Pavletić, L.; Peñil, P.; Perennes, C.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Priyadarshi, C.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.; Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.; Saturni, F. G.; Schleicher, B.; Schmidt, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Spolon, A.; Stamerra, A.; Strom, D.; Strzys, M.; Suda, Y.; Surić, T.; Takahashi, M.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone, A.; Ubach, S.; van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.; Ventura, S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.; Vovk, I.; Will, M.; Wunderlich, C.; Zarić, D.; Bissaldi, E.; Bonnoli, G.; Cutini, S.; D'Ammando, F.; Nabizadeh, A.; Marchini, A.; Orienti, M.; MAGIC Collaboration., We report here on the first multiwavelength (MWL) campaign on the blazar TXS 1515-273, undertaken in 2019 and extending from radio to very-high-energy gamma-rays (VHE). Up until now, this blazar had not been the subject of any detailed MWL observations. It has a rather hard photon index at GeV energies and was considered a candidate extreme high-synchrotron-peaked source. MAGIC observations resulted in the first-time detection of the source in VHE with a statistical significance of 7.6σ. The average integral VHE flux of the source is 6 ± 1 per cent of the Crab nebula flux above 400 GeV. X-ray coverage was provided by Swift-XRT, XMM-Newton, and NuSTAR. The long continuous X-ray observations were separated by ∼9 h, both showing clear hour scale flares. In the XMM-Newton data, both the rise and decay time-scales are longer in the soft X-ray than in the hard X-ray band, indicating the presence of a particle cooling regime. The X-ray variability time-scales were used to constrain the size of the emission region and the strength of the magnetic field. The data allowed us to determine the synchrotron peak frequency and classify the source as a flaring high, but not extreme synchrotron-peaked object. Considering the constraints and variability patterns from the X-ray data, we model the broad-band spectral energy distribution. We applied a simple one-zone model, which could not reproduce the radio emission and the shape of the optical emission, and a two-component leptonic model with two interacting components, enabling us to reproduce the emission from radio to VHE band. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society., The financial support of the German BMBF, MPG, and HGF; the Italian INFN and INAF; the Swiss National Fund SNF; the ERDF under the Spanish Ministerio de Ciencia e Innovacion (MICINN) (FPA201787859-P, FPA2017-85668-P, FPA2017-82729-C6-5-R, FPA201790566-REDC, PID2019-104114RB-C31, PID2019-104114RB-C32, PID2019-105510GB-C31, PID2019-107847RB-C41, PID2019107847RB-C42, PID2019-107847RB-C44, PID2019-107988GBC22); the Indian Department of Atomic Energy; the Japanese ICRR, the University of Tokyo, JSPS, and MEXT; the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1268/16.12.2019 and the Academy of Finland grant nr. 317637 and 320045 are gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia `Severo Ochoa' SEV-20160588, SEV-2017-0709 and CEX2019-000920-S, and `Maria de Maeztu' CEX2019-000918-M, the Unidad de Excelencia `Maria de Maeztu' MDM-2015-0509-18-2 and the `la Caixa' Foundation (fellowshipLCF/BQ/PI18/11630012), by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382 and by the Brazilian MCTIC, CNPq, and FAPERJ. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, theCommissariat à l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucleaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase from the following agencies is also gratefully acknowledged: the Istituto Nazionale di Astrofisica in Italy and the Centre National d'Etudes Spatiales in France.