Papers - OKUMURA Akira

Multiwavelength study of the galactic PeVatron candidate LHAASO J2108+5157

Abe, S; Aguasca-Cabot, A; Agudo, I; Crespo, NA; Antonelli, LA; Aramo, C; Arbet-Engels, A; Artero, M; Asano, K; Aubert, P; Baktash, A; Bamba, A; Larriva, AB; Baroncelli, L; de Almeida, UB; Barrio, JA; Batkovic, I; Baxter, J; González, JB; Bernardini, E; Bernardos, MI; Medrano, JB; Berti, A; Bhattacharjee, P; Biederbeck, N; Bigongiari, C; Bissaldi, E; Blanch, O; Bordas, P; Buisson, C; Bulgarelli, A; Burelli, I; Buscemi, M; Cardillo, M; Caroff, S; Carosi, A; Cassol, F; Cauz, D; Ceribella, G; Chai, Y; Cheng, K; Chiavassa, A; Chikawa, M; Chytka, L; Cifuentes, A; Contreras, JL; Cortina, J; Costantini, H; D'Amico, G; Dalchenko, M; De Angelis, A; de Lavergne, MD; De Lotto, B; de Menezes, R; Deleglise, G; Delgado, C; Mengual, JD; della Volpe, D; Dellaiera, M; Di Piano, A; Di Pierro, F; Di Tria, R; Di Venere, L; Díaz, C; Dominik, RM; Prester, DD; Donini, A; Dorner, D; Doro, M; Elsässer, D; Emery, G; Escudero, J; Ramazani, VF; Ferrara, G; Fiasson, A; Coromina, LF; Fröse, S; Fukami, S; Fukazawa, Y; Garcia, E; López, RG; Gasparrini, D; Geyer, D; Paiva, JG; Giglietto, N; Giordano, F; Giro, E; Gliwny, P; Godinovic, N; Grau, R; Green, D; Green, J; Gunji, S; Hackfeld, J; Hadasch, D; Hahn, A; Hashiyama, K; Hassan, T; Hayashi, K; Heckmann, L; Heller, M; Llorente, JH; Hirotani, K; Hoffmann, D; Horns, D; Houles, J; Hrabovsky, M; Hrupec, D; Hui, D; Hütten, M; Imazawa, R; Inada, T; Inome, Y; Ioka, K; Iori, M; Ishio, K; Iwamura, Y; Jacquemont, M; Martinez, IJ; Jurysek, J; Kagaya, M; Karas, V; Katagiri, H; Kataoka, J; Kerszberg, D; Kobayashi, Y; Kong, A; Kubo, H; Kushida, J; Lainez, M; Lamanna, G; Lamastra, A; Le Flour, T; Linhoff, M; Longo, F; López-Coto, R; López-Moya, M; López-Oramas, A; Loporchio, S; Lorini, A; Luque-Escamilla, PL; Majumdar, P; Makariev, M; Mandat, D; Manganaro, M; Manicò, G; Mannheim, K; Mariotti, M; Marquez, P; Marsella, G; Martí, J; Martinez, O; Martínez, G; Martínez, M; Marusevec, P; Mas-Aguilar, A; Maurin, G; Mazin, D; Guillen, EM; Micanovic, S; Miceli, D; Miener, T; Miranda, JM; Mirzoyan, R; Mizuno, T; Gonzalez, MM; Molina, E; Montaruli, T; Monteiro, I; Moralejo, A; Morcuende, D; Morselli, A; Mrakovcic, K; Murase, K; Nagai, A; Nakamori, T; Nickel, L; Nievas, M; Nishijima, K; Noda, K; Nosek, D; Nozaki, S; Ohishi, M; Ohtani, Y; Okazaki, N; Okumura, A; Orito, R; Otero-Santos, J; Palatiello, M; Paneque, D; Pantaleo, FR; Paoletti, R; Paredes, JM; Pavletic, L; Pech, M; Pecimotika, M; Pietropaolo, E; Pirola, G; Podobnik, F; Poireau, V; Polo, M; Pons, E; Prandini, E; Prast, J; Priyadarshi, C; Prouza, M; Rando, R; Rhode, W; Ribó, M; Rizi, V; Fernandez, GR; Saito, T; Sakurai, S; Sanchez, DA; Saric, T; Saturni, FG; Scherpenberg, J; Schleicher, B; Schmuckermaier, F; Schubert, JL; Schussler, F; Schweizer, T; Arroyo, MS; Sitarek, J; Sliusar, V; Spolon, A; Striskovic, J; Strzys, M; Suda, Y; Sunada, Y; Tajima, H; Takahashi, M; Takahashi, H; Takata, J; Takeishi, R; Tam, PHT; Tanaka, SJ; Tateishi, D; Temnikov, P; Terada, Y; Terauchi, K; Terzic, T; Teshima, M; Tluczykont, M; Tokanai, F; Torres, DF; Travnicek, P; Truzzi, S; Tutone, A; Uhlrich, G; Vacula, M; Acosta, MV; Verguilov, V; Viale, I; Vigliano, A; Vigorito, CF; Vitale, V; Voutsinas, G; Vovk, I; Vuillaume, T; Walter, R; Will, M; Yamamoto, T; Yamazaki, R; Yoshida, T; Yoshikoshi, T; Zywucka, N; Balbo, M; Eckert, D; Tramacere, A

ASTRONOMY & ASTROPHYSICS   Vol. 673   2023.5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Astronomy and Astrophysics  

Context. Several new ultrahigh-energy (UHE) γ-ray sources have recently been discovered by the Large High Altitude Air Shower Observatory (LHAASO) collaboration. These represent a step forward in the search for the so-called Galactic PeVatrons, the enigmatic sources of the Galactic cosmic rays up to PeV energies. However, it has been shown that multi-TeV γ-ray emission does not necessarily prove the existence of a hadronic accelerator in the source; indeed this emission could also be explained as inverse Compton scattering from electrons in a radiation-dominated environment. A clear distinction between the two major emission mechanisms would only be made possible by taking into account multi-wavelength data and detailed morphology of the source. Aims. We aim to understand the nature of the unidentified source LHAASO J2108+5157, which is one of the few known UHE sources with no very high-energy (VHE) counterpart. Methods. We observed LHAASO J2108+5157 in the X-ray band with XMM-Newton in 2021 for a total of 3.8 hours and at TeV energies with the Large-Sized Telescope prototype (LST-1), yielding 49 hours of good-quality data. In addition, we analyzed 12 years of Fermi-LAT data, to better constrain emission of its high-energy (HE) counterpart 4FGL J2108.0+5155. We used naima and jetset software packages to examine the leptonic and hadronic scenario of the multi-wavelength emission of the source. Results. We found an excess (3.7σ) in the LST-1 data at energies E > 3 TeV. Further analysis of the whole LST-1 energy range, assuming a point-like source, resulted in a hint (2.2σ) of hard emission, which can be described with a single power law with a photon index of Σ = 1.6 ± 0.2 the range of 0.3 - 100 TeV. We did not find any significant extended emission that could be related to a supernova remnant (SNR) or pulsar wind nebula (PWN) in the XMM-Newton data, which puts strong constraints on possible synchrotron emission of relativistic electrons. We revealed a new potential hard source in Fermi-LAT data with a significance of 4σ and a photon index of Σ = 1.9 ± 0.2, which is not spatially correlated with LHAASO J2108+5157, but including it in the source model we were able to improve spectral representation of the HE counterpart 4FGL J2108.0+5155. Conclusions. The LST-1 and LHAASO observations can be explained as inverse Compton-dominated leptonic emission of relativistic electrons with a cutoff energy of 100-30+70 TeV. The low magnetic field in the source imposed by the X-ray upper limits on synchrotron emission is compatible with a hypothesis of a PWN or a TeV halo. Furthermore, the spectral properties of the HE counterpart are consistent with a Geminga-like pulsar, which would be able to power the VHE-UHE emission. Nevertheless, the lack of a pulsar in the neighborhood of the UHE source is a challenge to the PWN/TeV-halo scenario. The UHE γ rays can also be explained as π0 decay-dominated hadronic emission due to interaction of relativistic protons with one of the two known molecular clouds in the direction of the source. Indeed, the hard spectrum in the LST-1 band is compatible with protons escaping a shock around a middle-aged SNR because of their high low-energy cut-off, but the origin of the HE γ-ray emission remains an open question.

DOI： 10.1051/0004-6361/202245086

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MAGIC observations provide compelling evidence of hadronic multi-TeV emission from the putative PeVatron SNR G106.3+2.7

Abe H., Abe S., Acciari V.A., Agudo I., Aniello T., Ansoldi S., Antonelli L.A., Arbet Engels A., Arcaro C., Artero M., Asano K., Baack D., Babić A., Baquero A., Barres De Almeida U., Barrio J.A., Batković I., Baxter J., Becerra González J., Bednarek W., Bernardini E., Bernardos M., Berti A., Besenrieder J., Bhattacharyya W., Bigongiari C., Biland A., Blanch O., Bonnoli G., Bošnjak , Burelli I., Busetto G., Carosi R., Carretero-Castrillo M., Castro-Tirado A.J., Ceribella G., Chai Y., Chilingarian A., Cikota S., 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., Del Popolo A., Delfino M., Delgado J., Delgado Mendez C., Depaoli D., Di Pierro F., Di Venere L., Do Souto Espiñeira E., Dominis Prester D., Donini A., Dorner D., Doro M., Elsaesser D., Emery G., Escudero J., Fallah Ramazani V., Fariña L., Fattorini A., Font L., Fruck C., Fukami S., Fukazawa Y., García López R.J., Garczarczyk M., Gasparyan S., Gaug M., Giesbrecht Paiva J.G., Giglietto N., Giordano F., Gliwny P., Godinović N., Grau R., Green D., Green J.G., Hadasch D., Hahn A., Hassan T., Heckmann L., Herrera J., Hrupec D., Hütten M., Imazawa R., Inada T., Iotov R., Ishio K., Jiménez Martínez I., Jormanainen J., Kerszberg D., Kobayashi Y., Kubo H., Kushida J.

Astronomy and Astrophysics   Vol. 671   2023.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Astronomy and Astrophysics  

Context. Certain types of supernova remnants (SNRs) in our Galaxy are assumed to be PeVatrons, capable of accelerating cosmic rays (CRs) to ∼ PeV energies. However, conclusive observational evidence for this has not yet been found. The SNR G106.3+2.7, detected at 1- 100 TeV energies by different γ-ray facilities, is one of the most promising PeVatron candidates. This SNR has a cometary shape, which can be divided into a head and a tail region with different physical conditions. However, in which region the 100 TeV emission is produced has not yet been identified because of the limited position accuracy and/or angular resolution of existing observational data. Additionally, it remains unclear as to whether the origin of the γ-ray emission is leptonic or hadronic. Aims. With the better angular resolution provided by new MAGIC data compared to earlier γ-ray datasets, we aim to reveal the acceleration site of PeV particles and the emission mechanism by resolving the SNR G106.3+2.7 with 0.1 resolution at TeV energies. Methods. We observed the SNR G106.3+2.7 using the MAGIC telescopes for 121.7 h in total - after quality cuts - between May 2017 and August 2019. The analysis energy threshold is ∼0.2 TeV, and the angular resolution is 0.07-0.1. We examined the γ-ray spectra of different parts of the emission, whilst benefitting from the unprecedented statistics and angular resolution at these energies provided by our new data. We also used measurements at other wavelengths such as radio, X-rays, GeV γ-rays, and 10 TeV γ-rays to model the emission mechanism precisely. Results. We detect extended γ-ray emission spatially coincident with the radio continuum emission at the head and tail of SNR G106.3+2.7. The fact that we detect a significant γ-ray emission with energies above 6.0 TeV from only the tail region suggests that the emissions above 10 TeV detected with air shower experiments (Milagro, HAWC, Tibet ASγ and LHAASO) are emitted only from the SNR tail. Under this assumption, the multi-wavelength spectrum of the head region can be explained with either hadronic or leptonic models, while the leptonic model for the tail region is in contradiction with the emission above 10 TeV and X-rays. In contrast, the hadronic model could reproduce the observed spectrum at the tail by assuming a proton spectrum with a cutoff energy of ∼1 PeV for that region. Such high-energy emission in this middle-aged SNR (4-10 kyr) can be explained by considering a scenario where protons escaping from the SNR in the past interact with surrounding dense gases at present. Conclusions. The γ-ray emission region detected with the MAGIC telescopes in the SNR G106.3+2.7 is extended and spatially coincident with the radio continuum morphology. The multi-wavelength spectrum of the emission from the tail region suggests proton acceleration up to ∼PeV, while the emission mechanism of the head region could either be hadronic or leptonic.

DOI： 10.1051/0004-6361/202244931

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Gamma-ray observations of MAXI J1820+070 during the 2018 outburst

Abe H., Abe S., Acciari V. A., Aniello T., Ansoldi S., Antonelli L. A., Engels A. Arbet, Arcaro C., Artero M., Asano K., Baack D., Babic A., Baquero A., de Almeida U. Barres, Barrio J. A., Batkovic I, Baxter J., Gonzalez J. Becerra, Bednarek W., Bernardini E., Bernardos M., Berti A., Besenrieder J., Bhattacharyya W., Bigongiari C., Biland A., Blanch O., Bonnoli G., Bosnjak Z., Burelli I, Busetto G., Carosi R., Carretero-Castrillo M., Ceribella G., Chai Y., Chilingarian A., Cikota S., 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., Del Popolo A., Delfino M., Delgado J., Mendez C. Delgado, Depaoli D., Di Pierro F., Di Venere L., Prester D. Dominis, Donini A., Dorner D., Doro M., Elsaesser D., Emery G., Ramazani V. Fallah, Farina L., Fattorini A., Font L., Fruck C., Fukami S., Fukazawa Y., Lopez R. J. Garcia, Garczarczyk M., Gasparyan S., Gaug M., Paiva J. G. Giesbrecht, Giglietto N., Giordano F., Gliwny P., Godinovic N., Grau R., Green D., Green J. G., Hadasch D., Hahn A., Hassan T., Heckmann L., Herrera J., Hoang J., Hrupec D., Hutten M., Imazawa R., Inada T., Iotov R., Ishio K., Martinez I. Jimenez, Jormanainen J., Kerszberg D., Kobayashi Y., Kubo H., Kushida J., Lamastra A., Lelas D., Leone F., Lindfors E., Linhoff L., Lombardi S., Longo F., Lopez-Coto R., Lopez-Moya M., Lopez-Oramas A., Loporchio S., Lorini A., Lyard E., Fraga B. Machado de Oliveira, Majumdar P., Makariev M., Maneva G., Mang N., Manganaro M., Mangano S., Mannheim K., Mariotti M., Martinez M., Aguilar A. Mas, Mazin D., Menchiari S., Mender S., Micanovic S., Miceli D., Miener T., Miranda J. M., Mirzoyan R., Molina E., Mondal H. A., Moralejo A., Morcuende D., Moreno V, Nakamori T., Nanci C., Nava L., Neustroev V, Rosillo M. Nievas, Nigro C., Nilsson K., Nishijima K., Ekoume T. Njoh, Noda K., Nozaki S., Ohtani Y., Oka T., Okumura A., Otero-Santos J., Paiano S., Palatiello M., Paneque D., Paoletti R., Paredes J. M., Pavletic L., Persic M., Pihet M., Pirola G., Podobnik F., Moroni P. G. Prada, Prandini E., Principe G., Priyadarshi C., Puljak I, Rhode W., Ribo M., Rico J., Righi C., Rugliancich A., Sahakyan N., Saito T., Sakurai S., Satalecka K., Saturni F. G., Schleicher B., Schmidt K., Schmuckermaier F., Schubert J. L., Schweizer T., Sitarek J., Sliusar V, Sobczynska D., Spolon A., Stamerra A., Striskovic J., Strom D., Strzys M., Suda Y., Suric T., Tajima H., Takahashi M., Takeishi R., Tavecchio F., Temnikov P., Terauchi K., Terzic T., Teshima M., Tosti L., Truzzi S., Tutone A., Ubach S., van Scherpenberg J., Acosta M. Vazquez, Ventura S., Verguilov V., Viale I, Vigorito C. F., Vitale V., Vovk I, Walter R., Will M., Wunderlich C., Yamamoto T., Zaric D., Abdalla H., Aharonian F., Benkhali F. Ait, Anguner E. O., Ashkar H., Backes M., Baghmanyan V, Martins V. Barbosa, Batzofin R., Becherini Y., Berge D., Bernloehr K., Bottcher M., Boisson C., Bolmont J., de Lavergne M. de Bony, Bradascio F., Breuhaus M., Brose R., Brun F., Bulik T., Bylund T., Cangemi F., Caroff S., Casanova S., Cerruti M., Chand T., Chandra S., Chen A., Chibueze O. U., Cotter G., Cristofari P., Mbarubucyeye J. Damascene, Devin J., Djannati-Atai A., Dmytriiev A., Egberts K., Ernenwein J-P, Fiasson A., de Clairfontaine G. Fichet, Fontaine G., Fuessling M., Funk S., Gabici S., Ghafourizadeh S., Giavitto G., Glawion D., Glicenstein J. F., Goswami P., Grolleron G., Hinton J. A., Horbe M., Hoischen C., Holch T. L., Holler M., Horns D., Huang Zhiqiu, Jamrozy M., Jankowsky F., Joshi V, Jung-Richardt I, Kasai E., Katarzynski K., Katz U., Khelifi B., Kluzniak W., Komin Nu, Kosack K., Kostunin D., Lang R. G., Le Stum S., Lemiere A., Lemoine-Goumard M., Lenain J-P, Leuschner F., Lohse T., Luashvili A., Lypova I, Mackey J., Majumdar J., Malyshev D., Malyshev D., Marandon V, Marchegiani P., Marti-Devesa G., Marx R., Maurin G., Meyer M., Mitchell A., Moderski R., Mohrmann L., Montanari A., Moulin E., Muller J., Murach T., Nakashima K., de Naurois M., Nayerhoda A., Niemiec J., Noel A. Pniyana, O'Brien P., Ohm S., Olivera-Nieto L., Wilhelmi E. de Ona, Ostrowski M., Panny S., Panter M., Parsons R. D., Poireau V, Prokhorov D. A., Prokoph H., Puehlhofer G., Punch M., Quirrenbach A., Reichherzer P., Reimer A., Reimer O., Renaud M., Rieger F., Rowell G., Rudak B., Ricarte H. Rueda, Ruiz-Velasco E., Sahakian V, Salzmann H., Santangelo A., Sasaki M., Schaefer J., Schussler F., Schutte H. M., Schwanke U., Shapopi J. N. S., Sol H., Specovius A., Spencer S., Stawarz L., Steenkamp R., Steinmassl S., Steppa C., Sushch I, Suzuki H., Takahashi T., Tanaka T., Thorpe-Morgan C., Tluczykont M., Tomankova L., Tsuji N., Uchiyama Y., van Eldik C., van Soelen B., Vecchi M., Veh J., Venter C., Vink J., Wagner S. J., White R., Wierzcholska A., Wong Yu Wun, Yusafzai A., Zacharias M., Zanin R., Zargaryan D., Zdziarski A. A., Zech A., Zhu S. J., Zouari S., Zywucka N., Acharyya A., Adams C. B., Batista P., Benbow W., Capasso M., Christiansen J. L., Chromey A. J., Errando M., Falcone A., Feng Q., Finley J. P., Foote G. M., Fortson L., Furniss A., Gent A., Hanlon W. E., Hervet O., Holder J., Hona B., Humensky T. B., Jin W., Kaaret P., Kertzman M., Kherlakian M., Kleiner T. K., Kumar S., Lang M. J., Lundy M., Maier G., McGrath C. E., Millis J., Moriarty P., Mukherjee R., O'Brien S., Ong R. A., Park N., Patel S. R., Pfrang K., Pohl M., Pueschel E., Quinn J., Ragan K., Reynolds P. T., Ribeiro D., Roache E., Ryan J. L., Sadeh I, Saha L., Santander M., Sembroski G. H., Shang R., Splettstoesser M., Tak D., Tucci J. V, Weinstein A., Williams D. A., Williamson T. J., Bosch-Ramon V, Celma C., Linares M., Russell D. M., Sala G.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   Vol. 517 ( 4 ) page： 4736 - 4751   2022.12

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Monthly Notices of the Royal Astronomical Society  

MAXI J1820+070 is a low-mass X-ray binary with a black hole (BH) as a compact object. This binary underwent an exceptionally bright X-ray outburst from 2018 March to October, showing evidence of a non-thermal particle population through its radio emission during this whole period. The combined results of 59.5 h of observations of the MAXI J1820+070 outburst with the H.E.S.S., MAGIC and VERITAS experiments at energies above 200 GeV are presented, together with Fermi-LAT data between 0.1 and 500 GeV, and multiwavelength observations from radio to X-rays. Gamma-ray emission is not detected from MAXI J1820+070, but the obtained upper limits and the multiwavelength data allow us to put meaningful constraints on the source properties under reasonable assumptions regarding the non-thermal particle population and the jet synchrotron spectrum. In particular, it is possible to show that, if a high-energy (HE) gamma-ray emitting region is present during the hard state of the source, its predicted flux should be at most a factor of 20 below the obtained Fermi-LAT upper limits, and closer to them for magnetic fields significantly below equipartition. During the state transitions, under the plausible assumption that electrons are accelerated up to ∼500 GeV, the multiwavelength data and the gamma-ray upper limits lead consistently to the conclusion that a potential HE and very-HE gamma-ray emitting region should be located at a distance from the BH ranging between 1011 and 1013 cm. Similar outbursts from low-mass X-ray binaries might be detectable in the near future with upcoming instruments such as CTA.

DOI： 10.1093/mnras/stac2686

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Active Galactic Nuclei population studies with the Cherenkov Telescope Array

Abdalla H., Abe H., Abe S., Abusleme A., Acero F., Acharyya A., Acín Portella V., Ackley K., Adam R., Adams C., Adhikari S.S., Aguado-Ruesga I., Agudo I., Aguilera R., Aguirre-Santaella A., Aharonian F., Alberdi A., Alfaro R., Alfaro J., Alispach C., Aloisio R., Alves Batista R., Amans J.P., Amati L., Amato E., Ambrogi L., Ambrosi G., Ambrosio M., Ammendola R., Anderson J., Anduze M., Angüner E.O., Antonelli L.A., Antonuccio V., Antoranz P., Anutarawiramkul R., Aragunde Gutierrez J., Aramo C., Araudo A., Araya M., Arbet-Engels A., Arcaro C., Arendt V., Armand C., Armstrong T., Arqueros F., Arrabito L., Arsioli B., Artero M., Asano K., Ascasíbar Y., Aschersleben J., Ashley M., Attinà P., Aubert P., Singh C.B., Baack D., Babic A., Backes M., Baena V., Bajtlik S., Baktash A., Balazs C., Balbo M., Ballester O., Ballet J., Balmaverde B., Bamba A., Bandiera R., Baquero Larriva A., Barai P., Barbier C., Barbosa Martins V., Barcelo M., Barkov M., Barnard M., Baroncelli L., Barres de Almeida U., Barrio J.A., Bastieri D., Batista P.I., Batkovic I., Bauer C., Bautista-González R., Baxter J., Becciani U., Becerra González J., Becherini Y., Beck G., Becker Tjus J., Bednarek W., Belfiore A., Bellizzi L., Belmont R., Benbow W., Berge D., Bernardini E., Bernardos M.I., Bernlöhr K., Berti A.

Proceedings of Science   Vol. 395   2022.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings of Science  

The Cherenkov Telescope Array (CTA) observatory is the next generation of ground-based imaging atmospheric Cherenkov telescopes (IACTs). Building on the strengths of current IACTs, CTA is designed to achieve an order of magnitude improvement in sensitivity, with unprecedented angular and energy resolution. CTA will also increase the energy reach of IACTs, observing photons in the energy range from 20 GeV to beyond 100 TeV. These advances in performance will see CTA heralding in a new era for high-energy astrophysics, with the emphasis shifting from source discovery, to population studies and precision measurements. In this talk we discuss CTA’s ability to conduct source population studies of γ-ray bright active galactic nuclei and how this ability will enhance our understanding on the redshift evolution of this dominant γ-ray source class.

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The Small-Sized Telescopes for the Southern Site of the Cherenkov Telescope Array

Amans J.P., Berge D., Bonanno G., Bose R.B., Brown A.M., Buckley J.H., Chadwick P.M., Conte F., Cotter G., De Frondat F., De Simone N., Dournaux J.L., Duffy C.A., Einecke S., Fasola G., Funk S., Giavitto G., Hinton J.A., Huet J.M., La Palombara N., Lapington J.S., Laporte P., Leach S.A., Leto G., Lloyd S., Lombardi S., Nayak A., Okumura A., Pareschi G., Prokoph H., Rébert E., Ross D., Rowell G., Scuderi S., Sol H., Spencer S., Tajima H., Trois A., Vercellone S., Vink J., Watson J.J., White R., Zech A.

Proceedings of Science   Vol. 395   2022.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings of Science  

The Cherenkov Telescope Array (CTA) will use three telescope sizes to efficiently detect cosmic gamma rays in the energy range from several tens of GeV to hundreds of TeV. The Small-Sized Telescopes (SSTs) will form the largest section of the array, covering an area of many square kilometres on the CTA southern site in Paranal, Chile. Up to 70 SSTs will be implemented by an international consortium of institutes and teams as an in-kind contribution to the CTA Observatory. The SSTs will provide unprecedented sensitivity to gamma rays above 1 TeV and the highest angular resolution of any instrument above the hard X-ray band. CTA has recently finalised the technology that will be used for the SSTs: the telescopes will be a dual-reflector design with a primary reflector of 4 m diameter, equipped with an SiPM-based camera with full waveform readout from ∼2000 channels covering a ∼9° field of view. The Schwarzschild-Couder optical configuration leads to a small plate-scale, and consequently a compact, cost-efficient camera. In this contribution, we describe the experience gained operating telescope and camera prototypes during the CTA preparatory phase, and the development of the final SST design.

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The Cherenkov Telescope Array: layout, design and performance

Abdalla H., Abe H., Abe S., Abusleme A., Acero F., Acharyya A., Acín Portella V., Ackley K., Adam R., Adams C., Adhikari S.S., Aguado-Ruesga I., Agudo I., Aguilera R., Aguirre-Santaella A., Aharonian F., Alberdi A., Alfaro R., Alfaro J., Alispach C., Aloisio R., Alves Batista R., Amans J.P., Amati L., Amato E., Ambrogi L., Ambrosi G., Ambrosio M., Ammendola R., Anderson J., Anduze M., Angüner E.O., Antonelli L.A., Antonuccio V., Antoranz P., Anutarawiramkul R., Aragunde Gutierrez J., Aramo C., Araudo A., Araya M., Arbet-Engels A., Arcaro C., Arendt V., Armand C., Armstrong T., Arqueros F., Arrabito L., Arsioli B., Artero M., Asano K., Ascasíbar Y., Aschersleben J., Ashley M., Attinà P., Aubert P., Singh C.B., Baack D., Babic A., Backes M., Baena V., Bajtlik S., Baktash A., Balazs C., Balbo M., Ballester O., Ballet J., Balmaverde B., Bamba A., Bandiera R., Baquero Larriva A., Barai P., Barbier C., Barbosa Martins V., Barcelo M., Barkov M., Barnard M., Baroncelli L., Barres de Almeida U., Barrio J.A., Bastieri D., Batista P.I., Batkovic I., Bauer C., Bautista-González R., Baxter J., Becciani U., Becerra González J., Becherini Y., Beck G., Becker Tjus J., Bednarek W., Belfiore A., Bellizzi L., Belmont R., Benbow W., Berge D., Bernardini E., Bernardos M.I., Bernlöhr K., Berti A.

Proceedings of Science   Vol. 395   2022.3

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The Cherenkov Telescope Array (CTA) will be the next generation very-high-energy gamma-ray observatory. CTA is expected to provide substantial improvement in accuracy and sensitivity with respect to existing instruments thanks to a tenfold increase in the number of telescopes and their state-of-the-art design. Detailed Monte Carlo simulations are used to further optimise the number of telescopes and the array layout, and to estimate the observatory performance using updated models of the selected telescope designs. These studies are presented in this contribution for the two CTA stations located on the island of La Palma (Spain) and near Paranal (Chile) and for different operation and observation conditions.

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The Cherenkov Telescope Array transient and multi-messenger program

Carosi A., López-Oramas A., Longo F., Abdalla H., Abe H., Abe S., Abusleme A., Acero F., Acharyya A., Acín Portella V., Ackley K., Adam R., Adams C., Adhikari S.S., Aguado-Ruesga I., Agudo I., Aguilera R., Aguirre-Santaella A., Aharonian F., Alberdi A., Alfaro R., Alfaro J., Alispach C., Aloisio R., Alves Batista R., Amans J.P., Amati L., Amato E., Ambrogi L., Ambrosi G., Ambrosio M., Ammendola R., Anderson J., Anduze M., Angüner E.O., Antonelli L.A., Antonuccio V., Antoranz P., Anutarawiramkul R., Aragunde Gutierrez J., Aramo C., Araudo A., Araya M., Arbet-Engels A., Arcaro C., Arendt V., Armand C., Armstrong T., Arqueros F., Arrabito L., Arsioli B., Artero M., Asano K., Ascasíbar Y., Aschersleben J., Ashley M., Attinà P., Aubert P., Singh C.B., Baack D., Babic A., Backes M., Baena V., Bajtlik S., Baktash A., Balazs C., Balbo M., Ballester O., Ballet J., Balmaverde B., Bamba A., Bandiera R., Baquero Larriva A., Barai P., Barbier C., Barbosa Martins V., Barcelo M., Barkov M., Barnard M., Baroncelli L., Barres de Almeida U., Barrio J.A., Bastieri D., Batista P.I., Batkovic I., Bauer C., Bautista-González R., Baxter J., Becciani U., Becerra González J., Becherini Y., Beck G., Becker Tjus J., Bednarek W., Belfiore A., Bellizzi L., Belmont R., Benbow W., Berge D., Bernardini E.

Proceedings of Science   Vol. 395   2022.3

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The Cherenkov Telescope Array (CTA) is a next generation ground-based very-high-energy gamma-ray observatory that will allow for observations in the >10 GeV range with unprecedented photon statistics and sensitivity. This will enable the investigation of the yet-marginally explored physics of short-time-scale transient events. CTA will thus become an invaluable instrument for the study of the physics of the most extreme and violent objects and their interactions with the surrounding environment. The CTA Transient program includes follow-up observations of a wide range of multi-wavelength and multi-messenger alerts, ranging from compact galactic binary systems to extragalactic events such as gamma-ray bursts (GRBs), core-collapse supernovae and bright AGN flares. In recent years, the first firm detection of GRBs by current Cherenkov telescope collaborations, the proven connection between gravitational waves and short GRBs, as well as the possible neutrino-blazar association with TXS 0506+056 have shown the importance of coordinated follow-up observations triggered by these different cosmic signals in the framework of the birth of multi-messenger astrophysics. In the next years, CTA will play a major role in these types of observations by taking advantage of its fast slewing (especially for the CTA Large Size Telescopes), large effective area and good sensitivity, opening new opportunities for time-domain astrophysics in an energy range not affected by selective absorption processes typical of other wavelengths. In this contribution we highlight the common approach adopted by the CTA Transients physics working group to perform the study of transient sources in the very-high-energy regime.

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Status and results of the prototype LST of CTA

Mazin D., Abe H., Aguasca A., Agudo I., Antonelli L.A., Aramo C., Armstrong T., Artero M., Asano K., Ashkar H., Aubert P., Baktash A., Bamba A., Baquero Larriva A., Baroncelli L., Barres de Almeida U., Barrio J.A., Batkovic I., Becerra González J., Bernardos M.I., Berti A., Biederbeck N., Bigongiari C., Blanch O., Bonnoli G., Bordas P., Bose D., Bulgarelli A., Burelli I., Buscemi M., Cardillo M., Caroff S., Carosi A., Cassol F., Cerruti M., Chai Y., Cheng K., Chikawa M., Chytka L., Contreras J.L., Cortina J., Costantini H., Dalchenko M., De Angelis A., de Bony de Lavergne M., Deleglise G., Delgado C., Delgado Mengual J., della Volpe D., Depaoli D., Di Pierro F., Di Venere L., Díaz C., Dominik R.M., Dominis Prester D., Donini A., Dorner D., Doro M., Elsässer D., Emery G., Escudero J., Fiasson A., Foffano L., Fonseca M.V., Freixas Coromina L., Fukami S., Fukazawa Y., Garcia E., Garcia López R., Giglietto N., Giordano F., Gliwny P., Godinovic N., Green D., Grespan P., Gunji S., Hackfeld J., Hadasch D., Hahn A., 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., Hütten M., Inada T., Inome Y., Iori M., Ishio K., Iwamura Y., Jacquemont M., Jimenez Martinez I., Jouvin L.

Proceedings of Science   Vol. 395   2022.3

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The Large-Sized Telescopes (LSTs) of Cherenkov Telescope Array (CTA) are designed for gamma-ray studies focusing on low energy threshold, high flux sensitivity, rapid telescope repositioning speed and a large field of view. Once the CTA array is complete, the LSTs will be dominating the CTA performance between 20 GeV and 150 GeV. During most of the CTA Observatory construction phase, however, the LSTs will be dominating the array performance until several TeVs. In this presentation we will report on the status of the LST-1 telescope inaugurated in La Palma, Canary islands, Spain in 2018. We will show the progress of the telescope commissioning, compare the expectations with the achieved performance, and give a glance of the first physics results.

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Southern African Large Telescope Spectroscopy of BL Lacs for the CTA project

Abdalla H., Abe H., Abe S., Abusleme A., Acero F., Acharyya A., Acín Portella V., Ackley K., Adam R., Adams C., Adhikari S.S., Aguado-Ruesga I., Agudo I., Aguilera R., Aguirre-Santaella A., Aharonian F., Alberdi A., Alfaro R., Alfaro J., Alispach C., Aloisio R., Alves Batista R., Amans J.P., Amati L., Amato E., Ambrogi L., Ambrosi G., Ambrosio M., Ammendola R., Anderson J., Anduze M., Angüner E.O., Antonelli L.A., Antonuccio V., Antoranz P., Anutarawiramkul R., Aragunde Gutierrez J., Aramo C., Araudo A., Araya M., Arbet-Engels A., Arcaro C., Arendt V., Armand C., Armstrong T., Arqueros F., Arrabito L., Arsioli B., Artero M., Asano K., Ascasíbar Y., Aschersleben J., Ashley M., Attinà P., Aubert P., Singh C.B., Baack D., Babic A., Backes M., Baena V., Bajtlik S., Baktash A., Balazs C., Balbo M., Ballester O., Ballet J., Balmaverde B., Bamba A., Bandiera R., Baquero Larriva A., Barai P., Barbier C., Barbosa Martins V., Barcelo M., Barkov M., Barnard M., Baroncelli L., Barres de Almeida U., Barrio J.A., Bastieri D., Batista P.I., Batkovic I., Bauer C., Bautista-González R., Baxter J., Becciani U., Becerra González J., Becherini Y., Beck G., Becker Tjus J., Bednarek W., Belfiore A., Bellizzi L., Belmont R., Benbow W., Berge D., Bernardini E., Bernardos M.I., Bernlöhr K., Berti A.

Proceedings of Science   Vol. 395   2022.3

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In the last two decades, very-high-energy gamma-ray astronomy has reached maturity: over 200 sources have been detected, both Galactic and extragalactic, by ground-based experiments. At present, Active Galactic Nuclei (AGN) make up about 40% of the more than 200 sources detected at very high energies with ground-based telescopes, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth and three quarters of which are classified as high-frequency peaked BL Lac objects. One challenge to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGN to be detected with the future Cherenkov Telescope Array (CTA) observatory will have no spectroscopic redshifts, compromising the reliability of BL Lac population studies, particularly of their cosmic evolution. We started an effort in 2019 to measure the redshifts of a large fraction of the AGN that are likely to be detected with CTA, using the Southern African Large Telescope (SALT). In this contribution, we present two results from an on-going SALT program focused on the determination of BL Lac object redshifts that will be relevant for the CTA observatory.

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Sensitivity of the Cherenkov Telescope Array to emission from the gamma-ray counterparts of neutrino events

Sergijenko O., Brown A.M., Fiorillo D.F.G., de León A.R., Satalecka K., Tung C.F., Reimann R., Glauch T., Taboada I., Abdalla H., Abe H., Abe S., Abusleme A., Acero F., Acharyya A., Acín Portella V., Ackley K., Adam R., Adams C., Adhikari S.S., Aguado-Ruesga I., Agudo I., Aguilera R., Aguirre-Santaella A., Aharonian F., Alberdi A., Alfaro R., Alfaro J., Alispach C., Aloisio R., Alves Batista R., Amans J.P., Amati L., Amato E., Ambrogi L., Ambrosi G., Ambrosio M., Ammendola R., Anderson J., Anduze M., Angüner E.O., Antonelli L.A., Antonuccio V., Antoranz P., Anutarawiramkul R., Aragunde Gutierrez J., Aramo C., Araudo A., Araya M., Arbet-Engels A., Arcaro C., Arendt V., Armand C., Armstrong T., Arqueros F., Arrabito L., Arsioli B., Artero M., Asano K., Ascasíbar Y., Aschersleben J., Ashley M., Attinà P., Aubert P., Singh C.B., Baack D., Babic A., Backes M., Baena V., Bajtlik S., Baktash A., Balazs C., Balbo M., Ballester O., Ballet J., Balmaverde B., Bamba A., Bandiera R., Baquero Larriva A., Barai P., Barbier C., Barbosa Martins V., Barcelo M., Barkov M., Barnard M., Baroncelli L., Barres de Almeida U., Barrio J.A., Bastieri D., Batista P.I., Batkovic I., Bauer C., Bautista-González R., Baxter J., Becciani U., Becerra González J., Becherini Y., Beck G., Becker Tjus J., Bednarek W.

Proceedings of Science   Vol. 395   2022.3

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We investigate the possibility of detection of the VHE gamma-ray counterparts to the neutrino astrophysical sources within the Neutrino Target of Opportunity (NToO) program of CTA using the populations simulated by the FIRESONG software to resemble the diffuse astrophysical neutrino flux measured by IceCube. We derive the detection probability for different zenith angles and geomagnetic field configurations. The difference in detectability of sources between CTA-North and CTA-South for the average geomagnetic field is not substantial. We investigate the effect of a higher night-sky background and the preliminary CTA Alpha layout on the detection probability.

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Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre

Abdalla H., Abe H., Abe S., Abusleme A., Acero F., Acharyya A., Acín Portella V., Ackley K., Adam R., Adams C., Adhikari S.S., Aguado-Ruesga I., Agudo I., Aguilera R., Aguirre-Santaella A., Aharonian F., Alberdi A., Alfaro R., Alfaro J., Alispach C., Aloisio R., Alves Batista R., Amans J.P., Amati L., Amato E., Ambrogi L., Ambrosi G., Ambrosio M., Ammendola R., Anderson J., Anduze M., Angüner E.O., Antonelli L.A., Antonuccio V., Antoranz P., Anutarawiramkul R., Aragunde Gutierrez J., Aramo C., Araudo A., Araya M., Arbet-Engels A., Arcaro C., Arendt V., Armand C., Armstrong T., Arqueros F., Arrabito L., Arsioli B., Artero M., Asano K., Ascasíbar Y., Aschersleben J., Ashley M., Attinà P., Aubert P., Singh C.B., Baack D., Babic A., Backes M., Baena V., Bajtlik S., Baktash A., Balazs C., Balbo M., Ballester O., Ballet J., Balmaverde B., Bamba A., Bandiera R., Baquero Larriva A., Barai P., Barbier C., Barbosa Martins V., Barcelo M., Barkov M., Barnard M., Baroncelli L., Barres de Almeida U., Barrio J.A., Bastieri D., Batista P.I., Batkovic I., Bauer C., Bautista-González R., Baxter J., Becciani U., Becerra González J., Becherini Y., Beck G., Becker Tjus J., Bednarek W., Belfiore A., Bellizzi L., Belmont R., Benbow W., Berge D., Bernardini E., Bernardos M.I., Bernlöhr K., Berti A.

Proceedings of Science   Vol. 395   2022.3

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High-energy gamma rays are promising tools to constrain or reveal the nature of dark matter, in particular Weakly Interacting Massive Particles. Being well into its pre-construction phase, the Cherenkov Telescope Array (CTA) will soon probe the sky in the 20 GeV - 300 TeV energy range. Thanks to its improved energy and angular resolutions as well as significantly larger effective area when compared to the current generation of Cherenkov telescopes, CTA is expected to probe heavier dark matter, with unprecedented sensitivity, reaching the thermal annihilation cross-section at 1 TeV. This talk will summarise the planned dark matter search strategies with CTA, focusing on the signal from the Galactic centre. As observed with the Fermi LAT at lower energies, this region is rather complex and CTA will be the first ground-based observatory sensitive to the large scale diffuse astrophysical emission from that region. We report on the collaboration effort to study the impact of such extended astrophysical backgrounds on the dark matter search, based on Fermi-LAT data in order to guide our observational strategies, taking into account various sources of systematic uncertainty.

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Sensitivity of CTA to gamma-ray emission from the Perseus galaxy cluster

Abdalla H., Abe H., Abe S., Abusleme A., Acero F., Acharyya A., Acín Portella V., Ackley K., Adam R., Adams C., Adhikari S.S., Aguado-Ruesga I., Agudo I., Aguilera R., Aguirre-Santaella A., Aharonian F., Alberdi A., Alfaro R., Alfaro J., Alispach C., Aloisio R., Alves Batista R., Amans J.P., Amati L., Amato E., Ambrogi L., Ambrosi G., Ambrosio M., Ammendola R., Anderson J., Anduze M., Angüner E.O., Antonelli L.A., Antonuccio V., Antoranz P., Anutarawiramkul R., Aragunde Gutierrez J., Aramo C., Araudo A., Araya M., Arbet-Engels A., Arcaro C., Arendt V., Armand C., Armstrong T., Arqueros F., Arrabito L., Arsioli B., Artero M., Asano K., Ascasíbar Y., Aschersleben J., Ashley M., Attinà P., Aubert P., Singh C.B., Baack D., Babic A., Backes M., Baena V., Bajtlik S., Baktash A., Balazs C., Balbo M., Ballester O., Ballet J., Balmaverde B., Bamba A., Bandiera R., Baquero Larriva A., Barai P., Barbier C., Barbosa Martins V., Barcelo M., Barkov M., Barnard M., Baroncelli L., Barres de Almeida U., Barrio J.A., Bastieri D., Batista P.I., Batkovic I., Bauer C., Bautista-González R., Baxter J., Becciani U., Becerra González J., Becherini Y., Beck G., Becker Tjus J., Bednarek W., Belfiore A., Bellizzi L., Belmont R., Benbow W., Berge D., Bernardini E., Bernardos M.I., Bernlöhr K., Berti A.

Proceedings of Science   Vol. 395   2022.3

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In these proceedings we summarize the current status of the study of the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse gamma-ray emission from the Perseus galaxy cluster. Gamma-ray emission is expected in galaxy clusters both from interactions of cosmic rays (CR) with the intra-cluster medium, or as a product of annihilation or decay of dark matter (DM) particles in case they are weakly interactive massive particles (WIMPs). The observation of Perseus constitutes one of the Key Science Projects to be carried out by the CTA Consortium. In this contribution, we focus on the DM-induced component of the flux. Our DM modelling includes the substructures we expect in the main halo which will boost the annihilation signal significantly. We adopt an ON/OFF observation strategy and simulate the expected gamma-ray signals. Finally we compute the expected CTA sensitivity using a likelihood maximization analysis including the most recent CTA instrument response functions. In absence of signal, we show that CTA will allow us to provide stringent and competitive constraints on TeV DM, especially for the case of DM decay.

Scopus

Searching for very-high-energy electromagnetic counterparts to gravitational-wave events with the Cherenkov Telescope Array

Patricelli B., Carosi A., Nava L., Seglar-Arroyo M., Schüssler F., Stamerra A., Adelfio A., Ashkar H., Bulgarelli A., Di Girolamo T., Di Piano A., Gasparetto T., Green J., Longo F., Agudo I., Berti A., Bissaldi E., Cella G., Circiello A., Covino S., Ghirlanda G., Humensky B., Inoue S., Lefaucheur J., Filipovic M., Razzano M., Ribeiro D., Sergijenko O., Stratta G., Vergani S., Abdalla H., Abe H., Abe S., Abusleme A., Acero F., Acharyya A., Acín Portella V., Ackley K., Adam R., Adams C., Adhikari S.S., Aguado-Ruesga I., Agudo I., Aguilera R., Aguirre-Santaella A., Aharonian F., Alberdi A., Alfaro R., Alfaro J., Alispach C., Aloisio R., Alves Batista R., Amans J.P., Amati L., Amato E., Ambrogi L., Ambrosi G., Ambrosio M., Ammendola R., Anderson J., Anduze M., Angüner E.O., Antonelli L.A., Antonuccio V., Antoranz P., Anutarawiramkul R., Aragunde Gutierrez J., Aramo C., Araudo A., Araya M., Arbet-Engels A., Arcaro C., Arendt V., Armand C., Armstrong T., Arqueros F., Arrabito L., Arsioli B., Artero M., Asano K., Ascasíbar Y., Aschersleben J., Ashley M., Attinà P., Aubert P., Singh C.B., Baack D., Babic A., Backes M., Baena V., Bajtlik S., Baktash A., Balazs C., Balbo M., Ballester O., Ballet J., Balmaverde B., Bamba A., Bandiera R., Baquero Larriva A.

Proceedings of Science   Vol. 395   2022.3

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The detection of electromagnetic (EM) emission following the gravitational wave (GW) event GW170817 opened the era of multi-messenger astronomy with GWs and provided the first direct evidence that at least a fraction of binary neutron star (BNS) mergers are progenitors of short Gamma-Ray Bursts (GRBs). GRBs are also expected to emit very-high energy (VHE, > 100 GeV) photons, as proven by the recent MAGIC and H.E.S.S. observations. One of the challenges for future multi-messenger observations will be the detection of such VHE emission from GRBs in association with GWs. In the next years, the Cherenkov Telescope Array (CTA) will be a key instrument for the EM follow-up of GW events in the VHE range, owing to its unprecedented sensitivity, rapid response, and capability to monitor a large sky area via scan-mode operation. We present the CTA GW follow-up program, with a focus on the searches for short GRBs possibly associated with BNS mergers. We investigate the possible observational strategies and we outline the prospects for the detection of VHE EM counterparts to transient GW events.

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ROBAST 3

Okumura A.

Proceedings of Science   Vol. 395   2022.3

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The ROOT-based simulator for ray tracing (ROBAST) is an open-source C++ library to simulate various types of cosmic-ray (CR) and gamma-ray telescopes. It is used in multiple purposes in all the different telescope designs of the Cherenkov Telescope Array and is a promising tool for use in other future projects in optics simulations. We have released ROBAST 3 that supports interference calculations in multilayer coating in addition to geometrical optics. Here, we present its new functionality and several recent applications in future CR telescopes.

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Reconstruction of stereoscopic CTA events using deep learning with CTLearn

Miener T., Nieto D., Brill A., Spencer S., Contreras J.L., Abdalla H., Abe H., Abe S., Abusleme A., Acero F., Acharyya A., Acín Portella V., Ackley K., Adam R., Adams C., Adhikari S.S., Aguado-Ruesga I., Agudo I., Aguilera R., Aguirre-Santaella A., Aharonian F., Alberdi A., Alfaro R., Alfaro J., Alispach C., Aloisio R., Alves Batista R., Amans J.P., Amati L., Amato E., Ambrogi L., Ambrosi G., Ambrosio M., Ammendola R., Anderson J., Anduze M., Angüner E.O., Antonelli L.A., Antonuccio V., Antoranz P., Anutarawiramkul R., Aragunde Gutierrez J., Aramo C., Araudo A., Araya M., Arbet-Engels A., Arcaro C., Arendt V., Armand C., Armstrong T., Arqueros F., Arrabito L., Arsioli B., Artero M., Asano K., Ascasíbar Y., Aschersleben J., Ashley M., Attinà P., Aubert P., Singh C.B., Baack D., Babic A., Backes M., Baena V., Bajtlik S., Baktash A., Balazs C., Balbo M., Ballester O., Ballet J., Balmaverde B., Bamba A., Bandiera R., Baquero Larriva A., Barai P., Barbier C., Barbosa Martins V., Barcelo M., Barkov M., Barnard M., Baroncelli L., Barres de Almeida U., Barrio J.A., Bastieri D., Batista P.I., Batkovic I., Bauer C., Bautista-González R., Baxter J., Becciani U., Becerra González J., Becherini Y., Beck G., Becker Tjus J., Bednarek W., Belfiore A., Bellizzi L., Belmont R., Benbow W.

Proceedings of Science   Vol. 395   2022.3

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The Cherenkov Telescope Array (CTA), conceived as an array of tens of imaging atmospheric Cherenkov telescopes (IACTs), is an international project for a next-generation ground-based gamma-ray observatory, aiming to improve on the sensitivity of current-generation instruments a factor of five to ten and provide energy coverage from 20 GeV to more than 300 TeV. Arrays of IACTs probe the very-high-energy gamma-ray sky. Their working principle consists of the simultaneous observation of air showers initiated by the interaction of very-high-energy gamma rays and cosmic rays with the atmosphere. Cherenkov photons induced by a given shower are focused onto the camera plane of the telescopes in the array, producing a multi-stereoscopic record of the event. This image contains the longitudinal development of the air shower, together with its spatial, temporal, and calorimetric information. The properties of the originating very-high-energy particle (type, energy, and incoming direction) can be inferred from those images by reconstructing the full event using machine learning techniques. In this contribution, we present a purely deep-learning driven, full-event reconstruction of simulated, stereoscopic IACT events using CTLearn. CTLearn is a package that includes modules for loading and manipulating IACT data and for running deep learning models, using pixel-wise camera data as input.

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Reconstruction of extensive air shower images of the first Large Size Telescope prototype of CTA using a novel likelihood technique

Emery G., Alispach C., Dalchenko M., Foffano L., Heller M., Montaruli T., Abe H., Aguasca A., Agudo I., Antonelli L.A., Aramo C., Armstrong T., Artero M., Asano K., Ashkar H., Aubert P., Baktash A., Bamba A., Baquero Larriva A., Baroncelli L., Barres de Almeida U., Barrio J.A., Batkovic I., Becerra González J., Bernardos M.I., Berti A., Biederbeck N., Bigongiari C., Blanch O., Bonnoli G., Bordas P., Bose D., Bulgarelli A., Burelli I., Buscemi M., Cardillo M., Caroff S., Carosi A., Cassol F., Cerruti M., Chai Y., Cheng K., Chikawa M., Chytka L., Contreras J.L., Cortina J., Costantini H., De Angelis A., de Bony de Lavergne M., Deleglise G., Delgado C., Delgado Mengual J., della Volpe D., Depaoli D., Di Pierro F., Di Venere L., Díaz C., Dominik R.M., Dominis Prester D., Donini A., Dorner D., Doro M., Elsässer D., Escudero J., Fiasson A., Fonseca M.V., Freixas Coromina L., Fukami S., Fukazawa Y., Garcia E., Garcia López R., Giglietto N., Giordano F., Gliwny P., Godinovic N., Green D., Grespan P., Gunji S., Hackfeld J., Hadasch D., Hahn A., Hassan T., Hayashi K., Heckmann L., Herrera Llorente J., Hirotani K., Hoffmann D., Horns D., Houles J., Hrabovsky M., Hrupec D., Hui D., Hütten M., Inada T., Inome Y., Iori M., Ishio K., Iwamura Y., Jacquemont M., Jimenez Martinez I.

Proceedings of Science   Vol. 395   2022.3

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Ground-based gamma-ray astronomy aims at reconstructing the energy and direction of gamma rays from the extensive air showers they initiate in the atmosphere. Imaging Atmospheric Cherenkov Telescopes (IACT) collect the Cherenkov light induced by secondary charged particles in extensive air showers (EAS), creating an image of the shower in a camera positioned in the focal plane of optical systems. This image is used to evaluate the type, energy and arrival direction of the primary particle that initiated the shower. This contribution shows the results of a novel reconstruction method based on likelihood maximization. The novelty with respect to previous likelihood reconstruction methods lies in the definition of a likelihood per single camera pixel, accounting not only for the total measured charge, but also for its development over time. This leads to more precise reconstruction of shower images. The method is applied to observations of the Crab Nebula acquired with the Large Size Telescope prototype (LST-1) deployed at the northern site of the Cherenkov Telescope Array.

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Prototype Schwarzschild-Couder Telescope for the Cherenkov Telescope Array: Commissioning the Optical System

Ribeiro D., Adams C.B., Ambrosi G., Ambrosio M., Aramo C., Batista P.I., Benbow W., Bertucci B., Bissaldi E., Bitossi M., Boiano A., Bonavolontà C., Bose R., Brill A., Buckley J.H., Cameron R.A., Canestrari R., Capasso M., Caprai M., Covault C.E., Depaoli D., Di Venere L., Errando M., Fegan S., Feng Q., Fiandrini E., Furniss A., Gent A., Giglietto N., Giordano F., Giro E., Halliday R., Hervet O., Humensky T.B., Incardona S., Ionica M., Jin W., Kieda D., Licciulli F., Loporchio S., Marsella G., Masone V., Meagher K., Meures T., Mode B.A.W., Mognet S.A.I., Mukherjee R., Nieto D., Okumura A., Otte N., Pantaleo F.R., Paoletti R., Pareschi G., Di Pierro F., Pueschel E., Riitano L., Roache E., Rousselle J., Rugliancich A., Santander M., Shang R., Stiaccini L., Taylor L.P., Tosti L., Tovmassian G., Tripodo G., Vagelli V., Valentino M., Vandenbroucke J., Vassiliev V.V., Williams D.A., Yu P.

Proceedings of Science   Vol. 395   2022.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings of Science  

A prototype Schwarzschild-Couder Telescope (pSCT) has been constructed at the Fred Lawrence Whipple Observatory as a candidate for the medium-sized telescopes of the Cherenkov Telescope Array Observatory (CTAO). CTAO is currently entering early construction phase of the project and once completed it will vastly improve very high energy gamma-ray detection component in multiwavelength and multi-messenger observations due to significantly improved sensitivity, angular resolution and field of view comparing to the current generation of the ground-based gamma-ray observatories H.E.S.S., MAGIC and VERITAS. The pSCT uses a dual aspheric mirror design with a 9.7 m primary mirror and 5.4 m secondary mirror, both of which are segmented. The Schwarzschild-Couder (SC) optical system (OS) selected for the prototype telescope achieves wide field of view of 8 degrees and simultaneously reduces the focal plane plate scale allowing an unprecedented compact (0.78m diameter) implementation of the high-resolution camera (6mm/0.067deg per imaging pixel with 11, 328 pixels) based on the silicon photo-multipliers (SiPMs). The OS of the telescope is designed to eliminate spherical and comatic aberrations and minimize astigmatism to radically improve off-axis imaging and consequently angular resolution across all the field of view with respect to the conventional single-mirror telescopes. Fast and high imaging resolution OS of the pSCT comes with the challenging submillimeter-precision custom alignment system, which was successfully demonstrated with an on-axis point spread function (PSF) of 2.9 arcmin prior to the first-light detection of the Crab Nebula in 2020. Ongoing commissioning activities aim to meet the on-axis PSF design goal of 2.6 arcmin, verify the off-axis performance of the pSCT OS, and develop techniques to maintain alignment stability over telescope structural deformations from pointing and temperature variations. In this contribution, we report on the commissioning status, the optical alignment procedures adopted for segmented OS, and alignment progress to verify and validate design requirements.

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Prototype Open Event Reconstruction Pipeline for the Cherenkov Telescope Array

Nöthe M., Kosack K., Nickel L., Peresano M., Abdalla H., Abe H., Abe S., Abusleme A., Acero F., Acharyya A., Acín Portella V., Ackley K., Adam R., Adams C., Adhikari S.S., Aguado-Ruesga I., Agudo I., Aguilera R., Aguirre-Santaella A., Aharonian F., Alberdi A., Alfaro R., Alfaro J., Alispach C., Aloisio R., Alves Batista R., Amans J.P., Amati L., Amato E., Ambrogi L., Ambrosi G., Ambrosio M., Ammendola R., Anderson J., Anduze M., Angüner E.O., Antonelli L.A., Antonuccio V., Antoranz P., Anutarawiramkul R., Aragunde Gutierrez J., Aramo C., Araudo A., Araya M., Arbet-Engels A., Arcaro C., Arendt V., Armand C., Armstrong T., Arqueros F., Arrabito L., Arsioli B., Artero M., Asano K., Ascasíbar Y., Aschersleben J., Ashley M., Attinà P., Aubert P., Singh C.B., Baack D., Babic A., Backes M., Baena V., Bajtlik S., Baktash A., Balazs C., Balbo M., Ballester O., Ballet J., Balmaverde B., Bamba A., Bandiera R., Baquero Larriva A., Barai P., Barbier C., Barbosa Martins V., Barcelo M., Barkov M., Barnard M., Baroncelli L., Barres de Almeida U., Barrio J.A., Bastieri D., Batista P.I., Batkovic I., Bauer C., Bautista-González R., Baxter J., Becciani U., Becerra González J., Becherini Y., Beck G., Becker Tjus J., Bednarek W., Belfiore A., Bellizzi L., Belmont R., Benbow W., Berge D.

Proceedings of Science   Vol. 395   2022.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings of Science  

The Cherenkov Telescope Array (CTA) is the next-generation gamma-ray observatory currently under construction. It will improve over the current generation of imaging atmospheric Cherenkov telescopes (IACTs) by a factor of five to ten in sensitivity and it will be able to observe the whole sky from a combination of two sites: a northern site in La Palma, Spain, and a southern one in Paranal, Chile. CTA will also be the first open gamma-ray observatory. Accordingly, the data analysis pipeline is developed as open-source software. The event reconstruction pipeline accepts raw data of the telescopes and processes it to produce suitable input for the higher-level science tools. Its primary tasks include reconstructing the physical properties of each recorded shower and providing the corresponding instrument response functions. ctapipe is a framework providing algorithms and tools to facilitate raw data calibration, image extraction, image parameterization and event reconstruction. Its main focus is currently the analysis of simulated data but it has also been successfully applied for the analysis of data obtained with the first CTA prototype telescopes, such as the Large-Sized Telescope 1 (LST-1). pyirf is a library to calculate IACT instrument response functions, needed to obtain physics results like spectra and light curves, from the reconstructed event lists. Building on these two, protopipe is a prototype for the event reconstruction pipeline for CTA. Recent developments in these software packages will be presented.

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Prospects for Galactic transient sources detection with the Cherenkov Telescope Array

López-Oramas A., Bulgarelli A., Chaty S., Chernyakova M., Gnatyk R., Hnatyk B., Kantzas D., Markoff S., McKeague S., Mereghetti S., Mestre E., di Piano A., Romano P., Sadeh I., Sergijenko O., Sidoli L., Spolon A., de Ona Wilhelmi E., Piano G., Zampieri L., Abdalla H., Abe H., Abe S., Abusleme A., Acero F., Acharyya A., Acín Portella V., Ackley K., Adam R., Adams C., Adhikari S.S., Aguado-Ruesga I., Agudo I., Aguilera R., Aguirre-Santaella A., Aharonian F., Alberdi A., Alfaro R., Alfaro J., Alispach C., Aloisio R., Alves Batista R., Amans J.P., Amati L., Amato E., Ambrogi L., Ambrosi G., Ambrosio M., Ammendola R., Anderson J., Anduze M., Angüner E.O., Antonelli L.A., Antonuccio V., Antoranz P., Anutarawiramkul R., Aragunde Gutierrez J., Aramo C., Araudo A., Araya M., Arbet-Engels A., Arcaro C., Arendt V., Armand C., Armstrong T., Arqueros F., Arrabito L., Arsioli B., Artero M., Asano K., Ascasíbar Y., Aschersleben J., Ashley M., Attinà P., Aubert P., Singh C.B., Baack D., Babic A., Backes M., Baena V., Bajtlik S., Baktash A., Balazs C., Balbo M., Ballester O., Ballet J., Balmaverde B., Bamba A., Bandiera R., Baquero Larriva A., Barai P., Barbier C., Barbosa Martins V., Barcelo M., Barkov M., Barnard M., Baroncelli L., Barres de Almeida U., Barrio J.A., Bastieri D.

Proceedings of Science   Vol. 395   2022.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings of Science  

Several types of Galactic sources, like magnetars, microquasars, novae or pulsar wind nebulae flares, display transient emission in the X-ray band. Some of these sources have also shown emission at MeV-GeV energies. However, none of these Galactic transients have ever been detected in the very-high-energy (VHE; E>100 GeV) regime by any Imaging Air Cherenkov Telescope (IACT). The Galactic Transient task force is a part of the Transient Working group of the Cherenkov Telescope Array (CTA) Consortium. The task force investigates the prospects of detecting the VHE counterpart of such sources, as well as their study following Target of Opportunity (ToO) observations. In this contribution, we will show some of the results of exploring the capabilities of CTA to detect and observe Galactic transients; we assume different array configurations and observing strategies.

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Physics Performance of the Large-Sized Telescope prototype of the Cherenkov Telescope Array

Abe H., Aguasca A., Agudo I., Antonelli L.A., Aramo C., Armstrong T., Artero M., Asano K., Ashkar H., Aubert P., Baktash A., Bamba A., Baquero Larriva A., Baroncelli L., Barres de Almeida U., Barrio J.A., Batkovic I., Becerra González J., Bernardos M.I., Berti A., Biederbeck N., Bigongiari C., Blanch O., Bonnoli G., Bordas P., Bose D., Bulgarelli A., Burelli I., Buscemi M., Cardillo M., Caroff S., Carosi A., Cassol F., Cerruti M., Chai Y., Cheng K., Chikawa M., Chytka L., Contreras J.L., Cortina J., Costantini H., Dalchenko M., De Angelis A., de Bony de Lavergne M., Deleglise G., Delgado C., Delgado Mengual J., della Volpe D., Depaoli D., Di Pierro F., Di Venere L., Díaz C., Dominik R.M., Dominis Prester D., Donini A., Dorner D., Doro M., Elsässer D., Emery G., Escudero J., Fiasson A., Foffano L., Fonseca M.V., Freixas Coromina L., Fukami S., Fukazawa Y., Garcia E., Garcia López R., Giglietto N., Giordano F., Gliwny P., Godinovic N., Green D., Grespan P., Gunji S., Hackfeld J., Hadasch D., Hahn A., 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., Hütten M., Inada T., Inome Y., Iori M., Ishio K., Iwamura Y., Jacquemont M., Jimenez Martinez I., Jouvin L., Jurysek J.

Proceedings of Science   Vol. 395   2022.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Proceedings of Science  

The Large-Sized Telescope (LST) prototype of the future Cherenkov Telescope Array (CTA) is located at the Northern site of CTA, on the Canary Island of La Palma. It is designed to provide optimal performance in the lowest part of the energy range covered by CTA, observing gamma rays down to energies of tens of GeV. The LST prototype started performing astronomical observations in November 2019 during the commissioning of the telescope and it has been taking data since then. In this contribution, we will present the tuning of the characteristics of the telescope in the Monte Carlo (MC) simulations to describe the data obtained, the estimation of its angular and energy resolution, and an evaluation of its sensitivity, both with simulations and with observations of the Crab Nebula.

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