A1 Refereed original research article in a scientific journal
Detection of the Geminga pulsar at energies down to 20 GeV with the LST-1 of CTAO
Authors: Abe, K.; Abe, S.; Abhishek, A.; Acero, F.; Aguasca-Cabot, A.; Agudo, I.; Alispach, C.; Ambrosino, D.; Ambrosino, F.; Antonelli, L. A.; Aramo, C.; Arbet-Engels, A.; Arcaro, C.; Arnesen, T. T. H.; Asano, K.; Aubert, P.; Baktash, A.; Balbo, M.; Bamba, A.; Baquero Larriva, A.; Barres de Almeida, U.; Barrio, J. A.; Barrios Jiménez, L.; Batkovic, I.; Baxter, J.; Becerra González, J.; Bernardini, E.; Bernete, J.; Berti, A.; Bezshyiko, I.; Bigongiari, C.; Bissaldi, E.; Blanch, O.; Bonnoli, G.; Bordas, P.; Borkowski, G.; Brunelli, G.; Bulgarelli, A.; Bunse, M.; Burelli, I.; Burmistrov, L.; Cardillo, M.; Caroff, S.; Carosi, A.; Carraro, R.; Carrasco, M. S.; Cassol, F.; Castrejón, N.; Cerasole, D.; Ceribella, G.; Cerviño Cortínez, A.; Chai, Y.; Cheng, K.; Chiavassa, A.; Chikawa, M.; Chon, G.; Chytka, L.; Cicciari, G. M.; Cifuentes, A.; Contreras, J. L.; Cortina, J.; Costantini, H.; Dalchenko, M.; Da Vela, P.; Dazzi, F.; De Angelis, A.; de Bony de Lavergne, M.; Del Burgo, R.; Delgado, C.; Delgado Mengual, J.; Dellaiera, M.; della Volpe, D.; De Lotto, B.; Del Peral, L.; de Menezes, R.; De Palma, G.; Díaz, C.; Di Piano, A.; Di Pierro, F.; Di Tria, R.; Di Venere, L.; Dominik, R. M.; Dominis Prester, D.; Donini, A.; Dore, D.; Dorner, D.; Doro, M.; Eisenberger, L.; Elsässer, D.; Emery, G.; Escudero, J.; Fallah Ramazani, V.; Ferrarotto, F.; Fiasson, A.; Foffano, L.; Fröse, S.; Fukazawa, Y.; Gallozzi, S.; Garcia López, R.; Garcia Soto, S.; Gasbarra, C.; Gasparrini, D.; Geyer, D.; Giesbrecht Paiva, J.; Giglietto, N.; Giordano, F.; Godinovic, N.; Gradetzke, T.; Grau, R.; Green, D.; Green, J.; Gunji, S.; Günther, P.; Hackfeld, J.; Hadasch, D.; Hahn, A.; Hashizume, M.; Hassan, T.; Hayashi, K.; Heckmann, L.; Heller, M.; Herrera Llorente, J.; Hirotani, K.; Hoffmann, D.; Horns, D.; Houles, J.; Hrabovsky, M.; Hrupec, D.; Hui, D.; Iarlori, M.; Imazawa, R.; Inada, T.; Inome, Y.; Inoue, S.; Ioka, K.; Iori, M.; Itokawa, T.; Iuliano, A.; Jahanvi, J.; Jimenez Martinez, I.; Jimenez Quiles, J.; Jorge Rodrigo, I.; Jurysek, J.; Kagaya, M.; Kalashev, O.; Karas, V.; Katagiri, H.; Kerszberg, D.; Kiyomot, T.; Kobayashi, Y.; Kohri, K.; Kong, A.; Kornecki, P.; Kubo, H.; Kushida, J.; Lacave, B.; Lainez, M.; Lamanna, G.; Lamastra, A.; Lemoigne, L.; Linhoff, M.; Lombardi, S.; Longo, F.; López-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio, S.; Lorini, A.; Lozano Bahilo, J.; Lucarelli, F.; Luciani, H.; Luque-Escamilla, P. L.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Mandat, D.; Manganaro, M.; Maniadakis, D. K.; Manicò, G.; Mannheim, K.; Marchesi, S.; Marini, F.; Mariotti, M.; Marquez, P.; Marsella, G.; Martí, J.; Martinez, O.; Martínez, G.; Martínez, M.; Mas-Aguilar, A.; Massa, M.; Maurin, G.; Mazin, D.; Méndez-Gallego, J.; Menon, S.; Mestre Guillen, E.; Micanovic, S.; Miceli, D.; Miener, T.; Miranda, J. M.; Mirzoyan, R.; Mizote, M.; Mizuno, T.; Molero Gonzalez, M.; Molina, E.; Montaruli, T.; Moralejo, A.; Morcuende, D.; Moreno Ramos, A.; Morselli, A.; Moya, V.; Muraishi, H.; Nagataki, S.; Nakamori, T.; Neronov, A.; Nieto Castaño, D.; Nievas Rosillo, M.; Nikolic, L.; Nishijima, K.; Noda, K.; Nosek, D.; Novotny, V.; Nozaki, S.; Ohishi, M.; Ohtani, Y.; Oka, T.; Okumura, A.; Orito, R.; Orsini, L.; Otero-Santos, J.; Ottanelli, P.; Palatiello, M.; Panebianco, G.; Paneque, D.; Pantaleo, F. R.; Paoletti, R.; Paredes, J. M.; Pech, M.; Pecimotika, M.; Peresano, M.; Pfeifle, F.; Pietropaolo, E.; Pihet, M.; Pirola, G.; Plard, C.; Podobnik, F.; Polo, M.; Prandini, E.; Prouza, M.; Rainò, S.; Rando, R.; Rhode, W.; Ribó, M.; Rizi, V.; Rodriguez Fernandez, G.; Rodríguez Frías, M. D.; Romano, P.; Roy, A.; Ruina, A.; Ruiz-Velasco, E.; Saito, T.; Sakurai, S.; Sanchez, D. A.; Sano, H.; Šarić, T.; Sato, Y.; Saturni, F. G.; Savchenko, V.; Schiavone, F.; Schleicher, B.; Schmuckermaier, F.; Schubert, J. L.; Schussler, F.; Schweizer, T.; Seglar Arroyo, M.; Siegert, T.; Silvestri, G.; Simongini, A.; Sitarek, J.; Sliusar, V.; Stamerra, A.; Strišković, J.; Strzys, M.; Suda, Y.; Sunny, A.; Tajima, H.; Takahashi, M.; Takata, J.; Takeishi, R.; Tam, P. H. T.; Tanaka, S. J.; Tateishi, D.; Tavernier, T.; Temnikov, P.; Terada, Y.; Terauchi, K.; Terzic, T.; Teshima, M.; Tluczykont, M.; Tokanai, F.; Tomura, T.; Torres, D. F.; Tramonti, F.; Travnicek, P.; Tripodo, G.; Tutone, A.; Vacula, M.; van Scherpenberg, J.; Vázquez Acosta, M.; Ventura, S.; Vercellone, S.; Verna, G.; Viale, I.; Vigliano, A.; Vigorito, C. F.; Visentin, E.; Vitale, V.; Voitsekhovskyi, V.; Voutsinas, G.; Vovk, I.; Vuillaume, T.; Walter, R.; Wan, L.; Will, M.; Wójtowicz, J.; Yamamoto, T.; Yamazaki, R.; Yao, Y.; Yeung, P. K. H.; Yoshida, T.; Yoshikoshi, T.; Zhang, W.
Publisher: EDP Sciences
Publication year: 2025
Journal: Astronomy and Astrophysics
Journal name in source: Astronomy & Astrophysics
Article number: A283
Volume: 698
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202554350
Web address : https://doi.org/10.1051/0004-6361/202554350
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/499271928
Context. Geminga is the third gamma-ray pulsar firmly detected by imaging atmospheric Cherenkov telescopes (IACTs) after the Crab and the Vela pulsars. Most of its emission is expected at tens of giga-electronvolts, and, out of the planned telescopes of the upcoming Cherenkov Telescope Array Observatory (CTAO), the Large-Sized Telescopes (LSTs) are the only ones with optimised sensitivity at these energies.
Aims. We aim to characterise the gamma-ray pulse shape and spectrum of Geminga as observed by the first LST (hereafter LST-1) of the Northern Array of CTAO. Furthermore, this study confirms the great performance and the improved energy threshold of the telescope, as low as 10 GeV for pulsar analysis, with respect to current-generation Cherenkov telescopes.
Methods. We analysed 60 hours of good-quality data taken by the LST-1 between December 2022 and March 2024 at zenith angles below 50°. Additionally, a new Fermi-LAT analysis of 16.6 years of data was carried out to extend the spectral analysis down to 100 MeV. Lastly, a detailed study of the systematic effects was performed.
Results. We report the detection of Geminga in the energy range between 20 and 65 GeV. Of the two peaks of the phaseogram, the second one, P2, is detected with a significance of 12.2σ, while the first (P1) reaches a significance level of 2.6σ. The best-fit model for the spectrum of P2 was found to be a power law with a spectral index of Γ = (4.5 ± 0.4stat)−0.6sys+0.2sys, compatible with the previous results obtained by the MAGIC Collaboration. No evidence of curvature is found in the LST-1 energy range. The joint fit with Fermi-LAT data confirms a preference for a sub-exponential cut-off over a pure exponential, even though both models fail to reproduce the data above several tens of giga-electronvolts. The overall results presented in this paper prove that the LST-1 is an excellent telescope for the observation of pulsars, and improved sensitivity is expected to be achieved with the full CTAO Northern Array.
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We gratefully acknowledge financial support from the following agencies and organisations: Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Fundacao de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ), Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Fundacao de Apoio a Ciencia, Tecnologia e Inovacao do Parana - Fundacao Araucaria, Ministry of Science, Technology, Innovations and Communications (MCTIC), Brasil; Ministry of Education and Science, National RI Roadmap Project DO1-153/28.08.2018, Bulgaria; Croatian Science Foundation (HrZZ) Project IP-2022-10-4595, Rudjer Boskovic Institute, University of Osijek, University of Rijeka, University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Zagreb, Faculty of Electrical Engineering and Computing, Croatia; Ministry of Education, Youth and Sports, MEYS LM2023047, EU/MEYS CZ.02.1.01/0.0/0.0/16_013/0001403, CZ.02.1.01/0.0/0.0/18_046/0016007, CZ.02.1.01/0.0/0.0/16_019/0000754, CZ.02.01.01/00/22_008/0004632 and CZ.02.01.01/00/23_015/0008197 Czech Republic; CNRS-IN2P3, the French Programme d'investissements d'avenir and the Enigmass Labex, This work has been done thanks to the facilities offered by the Univ. Savoie Mont Blanc - CNRS/IN2P3 MUST computing center, France; Max Planck Society, German Bundesministerium fuer Bildung und Forschung (Verbundforschung / ErUM), Deutsche Forschungsgemeinschaft (SFBs 876 and 1491), Germany; Istituto Nazionale di Astrofisica (INAF), Istituto Nazionale di Fisica Nucleare (INFN), Italian Ministry for University and Research (MUR), and the financial support from the European Union - Next Generation EU under the project IR0000012 - CTA+ (CUP C53C22000430006), announcement N.3264 on 28/12/2021: Rafforzamento e creazione di IR nell'ambito del Piano Nazionale di Ripresa e Resilienza (PNRR); ICRR, University of Tokyo, JSPS, MEXT, Japan; JST SPRING - JPMJSP2108; Narodowe Centrum Nauki, grant number 2019/34/E/ST9/00224, Poland; The Spanish groups acknowledge the Spanish Ministry of Science and Innovation and the Spanish Research State Agency (AEI) through the government budget lines PGE2022/28.06.000X.711.04, 28.06.000X.411.01 and 28.06.000X.711.04 of PGE 2023, 2024 and 2025, and grants PID2019-104114RB-C31, PID2019-107847RB-C44, PID2019-104114RB-C32, PID2019-105510GB-C31, PID2019-104114RB-C33, PID2019-107847RB-C43, PID2019-107847RB-C42, PID2019-107988GB-C22, PID2021-124581OB-I00, PID2021-125331NB-I00, PID2022-136828NB-C41, PID2022-137810NB-C22, PID2022-138172NB-C41, PID2022-138172NB-C42, PID2022-138172NB-C43, PID2022-139117NB-C41, PID2022-139117NB-C42, PID2022-139117NB-C43, PID2022-139117NB-C44, PID2022-136828NB-C42, PDC2023-145839-I00 funded by the Spanish MCIN/AEI/10.13039/501100011033 and and by ERDF/EU and NextGenerationEU PRTR; the Centro de Excelencia Severo Ochoa program through grants no. CEX2019-000920-S, CEX2020-001007-S, CEX2021-001131-S; the Unidad de Excelencia Maria de Maeztu program through grants no. CEX2019-000918-M, CEX2020-001058-M; the Ramon y Cajal program through grants RYC2021-032991-I funded by MICIN/AEI/10.13039/501100011033 and the European Union NextGenerationEU/PRTR and RYC2020-028639-I; the Juan de la Cierva-Incorporacion program through grant no. IJC2019-040315-I and Juan de la Cierva-formacion through grant JDC2022-049705-I. They also acknowledge the Atraccion de Talento program of Comunidad de Madrid through grant no. 2019-T2/TIC-12900; the project Tecnologias avanzadas para la exploracion del universo y sus componentes (PR47/21 TAU), funded by Comunidad de Madrid, by the Recovery, Transformation and Resilience Plan from the Spanish State, and by NextGenerationEU from the European Union through the Recovery and Resilience Facility; MAD4SPACE: Desarrollo de tecnologias habilitadoras para estudios del espacio en la Comunidad de Madrid (TEC-2024/TEC-182) project funded by Comunidad de Madrid; the La Caixa Banking Foundation, grant no. LCF/BQ/PI21/11830030; Junta de Andalucia under Plan Complementario de I+D+I (Ref. AST22_0001) and Plan Andaluz de Investigacion, Desarrollo e Innovacion as research group FQM-322; Project ref. AST22_00001_9 with funding from NextGenerationEU funds; the Ministerio de Ciencia, Innovacion y Universidades and its Plan de Recuperacion, Transformacion y Resiliencia; Consejeria de Universidad, Investigacion e Innovacion of the regional government of Andalucia and Consejo Superior de Investigaciones Cientificas, Grant CNS2023-144504 funded by MICIU/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR, the European Union's Recovery and Resilience Facility-Next Generation, in the framework of the General Invitation of the Spanish Government's public business entity Red.es to participate in talent attraction and retention programmes within Investment 4 of Component 19 of the Recovery, Transformation and Resilience Plan; Junta de Andalucia under Plan Complementario de I+D+I (Ref. AST22_00001), Plan Andaluz de Investigacion, Desarrollo e Innovacion (Ref. FQM-322). Programa Operativo de Crecimiento Inteligente FEDER 2014-2020 (Ref. ESFRI-2017-IAC-12), Ministerio de Ciencia e Innovacion, 15% co-financed by Consejeria de Economia, Industria, Comercio y Conocimiento del Gobierno de Canarias; the CERCA program and the grants 2021SGR00426 and 2021SGR00679, all funded by the Generalitat de Catalunya; and the European Union's NextGenerationEU (PRTR-C17.I1). This research used the computing and storage resources provided by the Port d'Informacio Cientifica (PIC) data center. State Secretariat for Education, Research and Innovation (SERI) and Swiss National Science Foundation (SNSF), Switzerland; The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreements No 262053 and No 317446; This project is receiving funding from the European Union's Horizon 2020 research and innovation programs under agreement No 676134; ESCAPE - The European Science Cluster of Astronomy & Particle Physics ESFRI Research Infrastructures has received funding from the European Union's Horizon 2020 research and innovation programme under Grant Agreement no. 824064.Author contribution: G. Brunelli: project coordination, LST-1 pulsar analysis (phaseogram and SED), Fermi-LAT phaseograms, joint fit of LST-1 and Fermi-LAT, systematic error estimation, results discussion. A. Mas-Aguilar: analysis coordination, cross-check on LST-1 pulsar analysis (phaseogram and SED), cross-check on joint fit of LST-1 and Fermi-LAT, systematic error estimation, results discussion. G. Ceribella: Fermi-LAT analysis, ephemeris production, results discussion. P. K. H. Yeung: cross-check on LST-1 pulsar analysis (phaseogram and SED), cross-check of the Fermi-LAT phaseogram, results discussion. R. Lopez-Coto: PI of the observations, project and analysis coordination, results discussion. M. Lopez-Moya: Fermi-LAT analysis, results discussion. All corresponding authors have participated in the paper drafting and edition. The rest of the authors have contributed in one or several of the following ways: design, construction, maintenance and operation of the instrument(s) used to acquire the data; preparation and/or evaluation of the observation proposals; data acquisition, processing, calibration and/or reduction; production of analysis tools and/or related Monte Carlo simulations; discussion and approval of the contents of the draft.
