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CTAO LST–1 observations of magnetar SGR 1935+2154: Deep limits on sub-second bursts and persistent tera-electronvolt emission

Context. The Galactic magnetar SGR 1935+2154 has exhibited prolific high-energy (HE) bursting activity in recent years. Aims. Investigating its potential tera-electronvolt counterpart could provide insights into the underlying mechanisms of magnetar emission and very high-energy (VHE) processes in extreme astrophysical environments. We aim to search for a possible tera-electronvolt counterpart to both its persistent and sub-second-scale burst emission. Methods. We analysed over 25 hour of observations from the Large-Sized Telescope prototype (LST−1) of the Cherenkov Telescope Array Observatory (CTAO) during periods of HE activity from SGR 1935+2154 in 2021 and 2022 to search for persistent emission. For bursting emission, we selected and analysed nine 0.1 s time windows centred around known short X-ray bursts, targeting potential sub-second-scale tera-electronvolt counterparts in a low-photon-statistics regime. Results. While no persistent or bursting emission was detected in our search, we establish upper limits for the tera-electronvolt emission of a short magnetar burst simultaneous to its soft gamma-ray flux. Specifically, for the brightest burst in our sample, the ratio between tera-electronvolt and X-ray flux is ≲10−3. Conclusions. The non-detection of either persistent or bursting tera-electronvolt emission from SGR 1935+2154 suggests that if such components exist, they may occur under specific conditions not covered by our observations. This aligns with theoretical predictions of VHE components in magnetar-powered fast radio bursts and the detection of MeV–GeV emission in giant magnetar flares. These findings underscore the potential of magnetars, fast radio bursts, and other fast transients as promising candidates for future observations in the low-photon-statistics regime with Imaging Atmospheric Cherenkov Telescopes, particularly with the CTAO.

Abe, K.Abe, S.Abhishek, A.Acero, F.Aguasca-Cabot, A.Agudo, I.Alispach, C.Ambrosino, D.Ambrosino, F.Aramo, C.Arbet-Engels, A.Arcaro, C.Asano, K.Aubert, P.Baktash, A.Balbo, M.Bamba, A.Baquero Larriva, A.Barres de Almeida, U.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.Cassol, F.Castrejón, N.Cerasole, D.Ceribella, G.Cerviño Cortínez, A.Chai, Y.Cheng, K.Chiavassa, A.Chikawa, M.Chon, G.Chytka, L.Cifuentes, A.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.Dominis Prester, D.Donini, A.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.Majumdar, P.Makariev, M.Mallamaci, M.Mandat, D.Manganaro, M.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.Mirzoyan, R.Mizuno, T.Molero Gonzalez, M.Molina, E.Montaruli, T.Moralejo, A.Morcuende, D.Morselli, A.Moya, V.Muraishi, H.Nagataki, S.Nakamori, T.Neronov, A.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.Otero-Santos, J.Palatiello, M.Paneque, D.Paoletti, R.Pech, M.Pecimotika, M.Peresano, M.Pietropaolo, E.Pirola, G.Podobnik, F.Frías García-Lago, F.Mizote, M.Antonelli, L. A.Arnesen, T. T. H.Barrio, J. A.Carrasco, M. S.Cicciari, G. M.Contreras, J. L.Dominik, R. M.Luque-Escamilla, P. L.Maniadakis, D. K.Miranda, J. M.Moreno Ramos, A.Nieto Castaño, D.Orsini, L.Ottanelli, P.Panebianco, G.Pantaleo, F. R.Paredes, J. M.Pfeifle, F.Pihet, M.Plard, C.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.(the CTAO-LST collaboration), Mereghetti, S.Parmiggiani, N.Vignali, C.Zanin, R.
No keywords available
Date:
February 2026
Volume:
706
Journal:
Astronomy & Astrophysics
DOI:
10.1051/0004-6361/202555431
Citation Key:
refId0
Publication Repository

VHE gamma-ray observations of bright BL Lacs with the Large-Sized Telescope prototype (LST-1) of the CTAO

Cherenkov Telescope Array Observatory (CTAO) is the next-generation ground-based γ-ray observatory operating in the energy range from 20 GeV up to 300 TeV, with two sites in La Palma (Spain) and Paranal (Chile). It will consist of telescopes of three sizes, covering different parts of the large energy range. We report on the performance of Large-Sized Telescope prototype (LST-1) in the detection and characterization of extragalactic γ-ray sources, with a focus on the reconstructed γ-ray spectra and variability of classical bright BL Lacertae objects, which were observed during the early commissioning phase of the instrument. LST-1 data from known bright γ-ray blazars-Markarian 421, Markarian 501, 1ES 1959+650, 1ES 0647+250, and PG 1553+113-were collected between July 10, 2020, and May 23, 2022, covering a zenith angle range of 4○ to 57○. The reconstructed light curves were analyzed using a Bayesian block algorithm to distinguish the different activity phases of each blazar. Simultaneous Fermi-LAT data were utilized to reconstruct the broadband γ-ray spectra for the sources during each activity phase. High-level reconstructed data in a format compatible with gammapy are provided together with measured light curves and spectral energy distributions (SEDs) for several bright blazars and an interpretation of the observed variability in long and short timescales. Simulations of historical flares are generated to evaluate the sensitivity of LST-1. This work represents the first milestone in monitoring bright BL Lacertae objects with a CTAO telescope.

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.Cerasole, D.Ceribella, G.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.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.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.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.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.Miceli, D.Miener, T.Miranda, J.~M.Mirzoyan, R.Frías García-Lago, F.Cortínez, A. Cerviñode Lavergne, M. de BonyDi Marco, G.Kiyomoto, T.Bahilo, J. LozanoGuillen, E. Mestre
High Energy Astrophysical Phenomena
Date:
Oct 2025
Journal:
mnras
DOI:
10.1093/mnras/staf1728
Eprint:
2510.03702
Citation Key:
2025MNRAS.tmp.1621A
Publication Repository

Constraining the TeV gamma-ray emission of SN 2024bch, a possible type IIn-L from a red supergiant progenitor: Multiwavelength observations and analysis of the progenitor

We present very high-energy optical photometry and spectroscopic observations of SN 2024bch in the nearby galaxy NGC 3206 (∼20 Mpc). We used gamma-ray observations performed with the first Large-Sized Telescope (LST-1) of the Cherenkov Telescope Array Observatory (CTAO) and optical observations with the Liverpool Telescope (LT) combined with data from public repositories to evaluate the general properties of the event and the progenitor star. No significant emission above the LST-1 energy threshold for this observation (∼100 GeV) was detected in the direction of SN 2024bch, and we computed an integral upper limit on the photon flux of Fγ(> 100 GeV)≤3.61 × 10‑12 cm‑2 s‑1 based on six nonconsecutive nights of observations with the LST-1, between 16 and 38 days after the explosion. Employing a general model for the gamma-ray flux emission, we found an upper limit on the mass-loss-rate to wind-velocity ratio of Ṁ/uw ≤ 10‑4 M⊙/ yr s/km M ˙ / u w ≤ 10 ‑ 4 M ⊙ yr s km , although gamma-gamma absorption could potentially have skewed this estimation, effectively weakening our constraint. From spectro-photometric observations we found progenitor parameters of Mpr = 11 – 20 M⊙ and Rpr = 531 ± 125 R⊙. Finally, using archival images from the Hubble Space Telescope, we constrained the luminosity of the progenitor star to log (Lpr/L⊙) ≤ 4.82 and its effective temperature to Tpr ≤ 4000 K. Our results suggest that SN 2024bch is a type IIn-L supernova that originated from a progenitor star consistent with a red supergiant. We show how the correct estimation of the mass-loss history of a supernova will play a major role in future multiwavelength observations.

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.Frías García-Lago, F.
gamma rays: generalsupernovae: generalsupernovae: individual: SN 2024bch
Date:
Oct 2025
Volume:
702
Journal:
aap
DOI:
10.1051/0004-6361/202554721
Citation Key:
2025A&A...702A.125A
Publication Repository

Detection of RS Oph with LST-1 and modelling of its HE/VHE gamma-ray emission

Context. The recurrent nova RS Ophiuchi (RS Oph) underwent a thermonuclear eruption in August 2021. In this event, RS Oph was detected by the High Energy Stereoscopic System (H.E.S.S.), the Major Atmospheric Gamma Imaging Cherenkov (MAGIC), and the first Large-Sized Telescope (LST-1) of the future Cherenkov Telescope Array Observatory (CTAO) at very-high gamma-ray energies above 100 GeV. This means that novae are a new class of very-high-energy (VHE) gamma-ray emitters. Aims. We report the analysis of the RS Oph observations with LST-1. We constrain the particle population that causes the observed emission in hadronic and leptonic scenarios. Additionally, we study the prospects of detecting further novae using LST-1 and the upcoming LST array of CTAO-North. Methods. We conducted target-of-opportunity observations with LST-1 from the first day of this nova event. The data were analysed in the framework of cta-lstchain and Gammapy, the official CTAO-LST reconstruction and analysis packages. One-zone hadronic and leptonic models were considered to model the gamma-ray emission of RS Oph using the spectral information from Fermi-LAT and LST-1, together with public data from the MAGIC and H.E.S.S. telescopes. Results. RS Oph was detected at 6.6σ with LST-1 in the first 6.35 hours of observations following the eruption. The hadronic scenario is preferred over the leptonic scenario considering a proton energy spectrum with a power-law model with an exponential cutoff whose position increases from (0.26 ± 0.08) TeV on day 1 up to (1.6 ± 0.6) TeV on day 4 after the eruption. The deep sensitivity and low energy threshold of the LST-1/LST array will allow us to detect faint novae and increase their discovery rate.

Abe, K.Abe, S.Abhishek, A.Acero, F.Aguasca-Cabot, A.Agudo, I.Alispach, C.Ambrosino, D.Antonelli, L.~A.Aramo, C.Arbet-Engels, A.Arcaro, C.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.Carrasco, M.~S.Cassol, F.Castrejón, N.Cerasole, D.Ceribella, G.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.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.Garcia López, R.Gasbarra, C.Gasparrini, D.Geyer, D.Giesbrecht Paiva, J.Giglietto, N.Giordano, F.Godinovic, N.Grau, R.Green, D.Green, J.Gunji, S.Günther, P.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.Iarlori, M.Imazawa, R.Inada, T.Inome, Y.Inoue, S.Ioka, K.Iori, M.Iuliano, A.Jahanvi, J.Jimenez Martinez, I.Jimenez Quiles, J.Jurysek, J.Kagaya, M.Kalashev, O.Karas, V.Katagiri, H.Kerszberg, D.Kobayashi, Y.Kohri, K.Kong, A.Kubo, H.Kushida, J.Lacave, B.Lainez, M.Lamanna, G.Lamastra, A.Lemoigne, L.Linhoff, M.Longo, F.López-Coto, R.López-Moya, M.López-Oramas, A.Loporchio, S.Lorini, A.Lozano Bahilo, J.Luciani, H.Luque-Escamilla, P.~L.Majumdar, P.Makariev, M.Mallamaci, M.Mandat, D.Manganaro, M.Manicò, G.Mannheim, K.Marchesi, S.Mariotti, M.Marquez, P.Marsella, G.Martí, J.Martinez, O.Martínez, G.Martínez, M.Mas-Aguilar, A.Maurin, G.Mazin, D.Méndez-Gallego, J.Menon, S.Mestre Guillen, E.Micanovic, S.Miceli, D.Miener, T.Miranda, J.~M.Alvarez Crespo, N.Bhattacharjee, P.Buscemi, M.Freixas Coromina, L.Gliwny, P.Kataoka, J.Mirzoyan, R.Mizuno, T.Molero Gonzalez, M.Molina, E.Montaruli, T.Moralejo, A.Morcuende, D.Morselli, A.Moya, V.Muraishi, H.Nagataki, S.Nakamori, T.
gamma rays: starsradiation mechanisms: non-thermalbinaries: closebinaries: symbioticnovaecataclysmic variablesstars: individual: RS OphiuchiAstrophysics - High Energy Astrophysical PhenomenaAstrophysics - Solar and Stellar Astrophysics
Date:
Mar 2025
Volume:
695
Number:
152
Journal:
aap
DOI:
10.1051/0004-6361/202452447
Eprint:
2503.13283
Citation Key:
2025A&A...695A.152A
Publication Repository

Detection of the Geminga pulsar at energies down to 20 GeV with the LST-1 of CTAO

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.

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.
astroparticle physicsstars: neutronpulsars: generalpulsars: individual: Geminga pulsargamma rays: starsHigh Energy Astrophysical Phenomena
Date:
Jun 2025
Volume:
698
Number:
283
Journal:
aap
DOI:
10.1051/0004-6361/202554350
Eprint:
2505.21632
Citation Key:
2025A&A...698A.283A
Publication Repository

GRB 221009A: Observations with LST-1 of CTAO and Implications for Structured Jets in Long Gamma-Ray Bursts

GRB 221009A is the brightest gamma-ray burst (GRB) observed to date. Extensive observations of its afterglow emission across the electromagnetic spectrum were performed, providing the first strong evidence of a jet with a nontrivial angular structure in a long GRB. We carried out an extensive observation campaign in very-high-energy (VHE) gamma rays with the first Large-Sized Telescope of the future Cherenkov Telescope Array Observatory starting on 2022 October 10, about 1 day after the burst. A dedicated analysis of the GRB 221009A data is performed to account for the different moonlight conditions under which data were recorded. We find an excess of gamma-like events with a statistical significance of 4.1σ during the observations taken 1.33 days after the burst, followed by background-compatible results for the later days. The results are compared with various models of afterglows from structured jets that are consistent with the published multiwavelength data but entail significant quantitative and qualitative differences in the VHE emission after 1 day. We disfavor models that imply VHE flux at 1 day considerably above 10‑11 erg cm‑2 s‑1. Our late-time VHE observations can help disentangle the degeneracy among the models and provide valuable new insight into the structure of GRB jets.

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.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.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.Miceli, D.Miener, T.Miranda, J.~M.Mirzoyan, R.Frías García-Lago, F.Mizote, M.
High Energy Astrophysical PhenomenaGamma-ray burstsTransient sourcesNon-thermal radiation sources62918511119
Date:
Aug 2025
Volume:
988
Number:
2
Journal:
apjl
DOI:
10.3847/2041-8213/ade4cf
Eprint:
2507.03077
Citation Key:
2025ApJ...988L..42A

A detailed study of the very high-energy Crab pulsar emission with the LST-1

Context. To date, three pulsars have been firmly detected by imaging atmospheric Cherenkov telescopes (IACTs). Two of them reached the TeV energy range, challenging models of very high-energy (VHE) emission in pulsars. More precise observations are needed to better characterize pulsar emission at these energies. The LST-1 is the prototype of the large-sized telescopes, which will be part of the Cherenkov Telescope Array Observatory (CTAO). Its improved performance over previous IACTs makes it well suited for studying pulsars. Aims. In this work we study the Crab pulsar emission with the LST-1, improving upon and complementing the results from other telescopes. Crab pulsar observations can also be used to characterize the potential of the LST-1 to study other pulsars and detect new ones. Methods. We analyzed a total of ∼103 hours of gamma-ray observations of the Crab pulsar conducted with the LST-1 in the period from September 2020 to January 2023. The observations were carried out at zenith angles of less than 50 degrees. To characterize the Crab pulsar emission over a broader energy range, a new analysis of the Fermi/LAT data, including ∼14 years of observations, was also performed. Results. The Crab pulsar phaseogram, long-term light curve, and phase-resolved spectra are reconstructed with the LST-1 from 20 GeV to 450 GeV for the first peak and up to 700 GeV for the second peak The pulsed emission is detected with a significance level of 15.2σ. The two characteristic emission peaks of the Crab pulsar are clearly detected (> 10σ), as is the so-called bridge emission between them (5.7σ). We find that both peaks are described well by power laws, with spectral indices of ∼3.44 and ∼3.03, respectively. The joint analysis of Fermi/LAT and LST-1 data shows a good agreement between the two instruments in their overlapping energy range. The detailed results obtained from the first observations of the Crab pulsar with the LST-1 show the potential that CTAO will have to study this type of source.

Abe, K.Abe, S.Abhishek, A.Acero, F.Aguasca-Cabot, A.Agudo, I.Antonelli, L.~A.Aramo, C.Arbet-Engels, A.Arcaro, C.Asano, K.Aubert, P.Baktash, A.Bamba, A.Baquero Larriva, A.Barres de Almeida, U.Barrio, J.~A.Batkovic, I.Baxter, J.Bernardini, E.Berti, A.Bigongiari, C.Bissaldi, E.Blanch, O.Bonnoli, G.Bordas, P.Brunelli, G.Bulgarelli, A.Burelli, I.Burmistrov, L.Cardillo, M.Caroff, S.Carosi, A.Carrasco, M.~S.Cassol, F.Castrejón, N.Cerasole, D.Ceribella, G.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.Delgado, C.Delgado Mengual, J.Dellaiera, M.della Volpe, D.De Lotto, B.Del Peral, L.de Menezes, R.Díaz, C.Di Piano, A.Di Pierro, F.Di Tria, R.Di Venere, L.Dominik, R.~M.Dominis Prester, D.Donini, A.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.Garcia López, R.Gasbarra, C.Gasparrini, D.Geyer, D.Giesbrecht Paiva, J.Giglietto, N.Giordano, F.Godinovic, N.Grau, R.Green, D.Green, J.Gunji, S.Günther, P.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.Iarlori, M.Imazawa, R.Inada, T.Inome, Y.Ioka, K.Iori, M.Jimenez Martinez, I.Jimenez Quiles, J.Jurysek, J.Kagaya, M.Karas, V.Katagiri, H.Kerszberg, D.Kobayashi, Y.Kohri, K.Kong, A.Kubo, H.Kushida, J.Lainez, M.Lamanna, G.Lamastra, A.Lemoigne, L.Linhoff, M.Longo, F.López-Coto, R.López-Moya, M.López-Oramas, A.Loporchio, S.Lorini, A.Lozano Bahilo, J.Luque-Escamilla, P.~L.Majumdar, P.Makariev, M.Mallamaci, M.Mandat, D.Manganaro, M.Manicò, G.Mannheim, K.Marchesi, S.Mariotti, M.Marquez, P.Marsella, G.Martí, J.Martinez, O.Martínez, G.Martínez, M.Mas-Aguilar, A.Maurin, G.Mazin, D.Mestre Guillen, E.Micanovic, S.Miceli, D.Miener, T.Miranda, J.~M.Alvarez Crespo, N.Bhattacharjee, P.Buscemi, M.Freixas Coromina, L.Gliwny, P.Kataoka, J.Mirzoyan, R.Mizuno, T.Molero Gonzalez, M.Molina, E.Montaruli, T.Moralejo, A.Morcuende, D.Morselli, A.Moya, V.Muraishi, H.Nagataki, S.Nakamori, T.Artero, M.Baroncelli, L.Becerra Gonzáilez, J.Bernete Medrano, J.Cauz, D.Gavira, L.Neronov, A.Nickel, L.Nievas Rosillo, M.Nikolic, L.Nishijima, K.Noda, K.Nosek, D.Novotny, V.Nozaki, S.Ohishi, M.Ohtani, Y.Oka, T.Okumura, A.
astroparticle physicsstars: neutronpulsars: generalgamma rays: starsAstrophysics - High Energy Astrophysical Phenomenapulsars: individual: Crab pulsar
Date:
Oct 2024
Volume:
690
Number:
167
Journal:
aap
DOI:
10.1051/0004-6361/202450059
Eprint:
2407.02343
Citation Key:
2024A&A...690A.167A
Publication Repository

Observations of the Crab Nebula and Pulsar with the Large-sized Telescope Prototype of the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) is a next-generation ground-based observatory for gamma-ray astronomy at very high energies. The Large-Sized Telescope prototype (LST-1) is located at the CTA-North site, on the Canary Island of La Palma. LSTs are designed to provide optimal performance in the lowest part of the energy range covered by CTA, down to ≃20 GeV. LST-1 started performing astronomical observations in 2019 November, during its commissioning phase, and it has been taking data ever since. We present the first LST-1 observations of the Crab Nebula, the standard candle of very-high-energy gamma-ray astronomy, and use them, together with simulations, to assess the performance of the telescope. LST-1 has reached the expected performance during its commissioning period-only a minor adjustment of the preexisting simulations was needed to match the telescope's behavior. The energy threshold at trigger level is around 20 GeV, rising to ≃30 GeV after data analysis. Performance parameters depend strongly on energy, and on the strength of the gamma-ray selection cuts in the analysis: angular resolution ranges from 0.°12-0.°40, and energy resolution from 15%-50%. Flux sensitivity is around 1.1% of the Crab Nebula flux above 250 GeV for a 50 hr observation (12% for 30 minutes). The spectral energy distribution (in the 0.03-30 TeV range) and the light curve obtained for the Crab Nebula agree with previous measurements, considering statistical and systematic uncertainties. A clear periodic signal is also detected from the pulsar at the center of the Nebula.

Abe, K.Abe, S.Aguasca-Cabot, A.Agudo, I.Antonelli, L.~A.Aramo, C.Arbet-Engels, A.Arcaro, C.Asano, K.Aubert, P.Baktash, A.Bamba, A.Baquero Larriva, A.Barres de Almeida, U.Barrio, J.~A.Batkovic, I.Baxter, J.Becerra González, J.Bernardini, E.Berti, A.Bigongiari, C.Bissaldi, E.Blanch, O.Bonnoli, G.Bordas, P.Bulgarelli, A.Burelli, I.Cardillo, M.Caroff, S.Carosi, A.Cassol, F.Ceribella, G.Chai, Y.Cheng, K.Chiavassa, A.Chikawa, M.Chytka, L.Cifuentes, A.Contreras, J.~L.Cortina, J.Costantini, H.Dalchenko, M.De Angelis, A.de Bony de Lavergne, M.Delgado, C.Delgado Mengual, J.Dellaiera, M.della Volpe, D.De Lotto, B.de Menezes, R.Díaz, C.Di Piano, A.Di Pierro, F.Di Tria, R.Di Venere, L.Dominik, R.~M.Dominis Prester, D.Donini, A.Dorner, D.Doro, M.Elsässer, D.Emery, G.Escudero, J.Fallah Ramazani, V.Ferrarotto, F.Fiasson, A.Fröse, S.Fukazawa, Y.Garcia López, R.Gasbarra, C.Gasparrini, D.Giesbrecht Paiva, J.Giglietto, N.Giordano, F.Godinovic, N.Grau, R.Green, D.Green, J.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.Iarlori, M.Imazawa, R.Inada, T.Inome, Y.Ioka, K.Iori, M.Jimenez Martinez, I.Jurysek, J.Kagaya, M.Karas, V.Katagiri, H.Kerszberg, D.Kobayashi, Y.Kong, A.Kubo, H.Kushida, J.Lainez, M.Lamanna, G.Lamastra, A.Linhoff, M.Longo, F.López-Coto, R.López-Moya, M.López-Oramas, A.Loporchio, S.Lorini, A.Luque-Escamilla, P.~L.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.Mas-Aguilar, A.Maurin, G.Mazin, D.Mestre Guillen, E.Micanovic, S.Miceli, D.Miener, T.Miranda, J.~M.Alvarez Crespo, N.Bhattacharjee, P.Buscemi, M.Freixas Coromina, L.Gliwny, P.Kataoka, J.Mirzoyan, R.Mizuno, T.Molero Gonzalez, M.Molina, E.Montaruli, T.Moralejo, A.Morcuende, D.Morselli, A.Nagataki, S.Nakamori, T.Artero, M.Baroncelli, L.Bernete Medrano, J.Cauz, D.Nickel, L.Nishijima, K.Noda, K.Nosek, D.Nozaki, S.Ohishi, M.Ohtani, Y.Oka, T.Okumura, A.Abe, H.Bernardos, M.~I.Biederbeck, N.D'Amico, G.Deleglise, G.Depaoli, D.Ferrara, G.Fukami, S.Garcia, E.Hashiyama, K.Hütten, M.Ishio, K.Jacquemont, M.Le Flour, T.Giro, E.Monteiro, I.Murase, K.Nievas, M.Orito, R.Otero-Santos, J.Palatiello, M.Paneque, D.Borghese, A.Geyer, F.Iwamura, Y.Marusevec, P.Mrakovcic, K.Nagai, A.Okazaki, N.
Astrophysics - High Energy Astrophysical PhenomenaAstrophysics - Instrumentation and Methods for AstrophysicsGamma-ray astronomyGamma-ray sourcesAstronomy data analysisPulsar wind nebulaePulsars628633185822151306
Date:
Oct 2023
Volume:
956
Number:
2
Journal:
The Astrophysical Journal
DOI:
10.3847/1538-4357/ace89d
Eprint:
2306.12960
Citation Key:
2023ApJ...956...80A
Publication Repository

Star tracking for pointing determination of Imaging Atmospheric Cherenkov Telescopes. Application to the Large-Sized Telescope of the Cherenkov Telescope Array

We present a novel approach to the determination of the pointing of Imaging Atmospheric Cherenkov Telescopes (IACTs) using the trajectories of the stars in their camera's field of view. The method starts with the reconstruction of the star positions from the Cherenkov camera data, taking into account the point spread function of the telescope, to achieve a satisfying reconstruction accuracy of the pointing position. A simultaneous fit of all reconstructed star trajectories is then performed with the orthogonal distance regression (ODR) method. ODR allows us to correctly include the star position uncertainties and use the time as an independent variable. Having the time as an independent variable in the fit makes it better suitable for various star trajectories. This method can be applied to any IACT and requires neither specific hardware nor interface or special data-taking mode. In this paper, we use the Large-Sized Telescope (LST) data to validate it as a useful tool to improve the determination of the pointing direction during regular data taking. The simulation studies show that the accuracy and precision of the method are comparable with the design requirements on the pointing accuracy of the LST (≤14″). With the typical LST event acquisition rate of 10 kHz, the method can achieve up to 50 Hz pointing monitoring rate, compared to 𝒪(1) Hz achievable with standard techniques. The application of the method to the LST prototype (LST-1) commissioning data shows the stable pointing performance of the telescope.

Abe, K.Abe, S.Aguasca-Cabot, A.Agudo, I.Antonelli, L.~A.Aramo, C.Arbet-Engels, A.Asano, K.Aubert, P.Baktash, A.Bamba, A.Baquero Larriva, A.Barres de Almeida, U.Barrio, J.~A.Batkovic, I.Baxter, J.Becerra González, J.Bernardini, E.Berti, A.Bigongiari, C.Bissaldi, E.Blanch, O.Bonnoli, G.Bordas, P.Bulgarelli, A.Burelli, I.Burmistrov, L.Cardillo, M.Caroff, S.Carosi, A.Cassol, F.Ceribella, G.Chai, Y.Cheng, K.Chiavassa, A.Chikawa, M.Chytka, L.Cifuentes, A.Contreras, J.~L.Cortina, J.Costantini, H.Dalchenko, M.De Angelis, A.de Bony de Lavergne, M.Delgado, C.Delgado Mengual, J.Dellaiera, M.della Volpe, D.De Lotto, B.de Menezes, R.Díaz, C.Di Piano, A.Di Pierro, F.Di Tria, R.Di Venere, L.Dominik, R.~M.Dominis Prester, D.Donini, A.Dorner, D.Doro, M.Elsässer, D.Emery, G.Escudero, J.Fallah Ramazani, V.Ferrarotto, F.Fiasson, A.Fröse, S.Fukazawa, Y.Garcia López, R.Gasbarra, C.Gasparrini, D.Geyer, D.Giesbrecht Paiva, J.Giglietto, N.Giordano, F.Godinovic, N.Grau, R.Green, D.Green, J.Gunji, S.Günther, P.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.Iarlori, M.Imazawa, R.Inada, T.Inome, Y.Ioka, K.Iori, M.Jimenez Martinez, I.Jurysek, J.Kagaya, M.Karas, V.Katagiri, H.Kerszberg, D.Kobayashi, Y.Kohri, K.Kong, A.Kubo, H.Kushida, J.Lainez, M.Lamanna, G.Lamastra, A.Linhoff, M.Longo, F.López-Coto, R.López-Oramas, A.Loporchio, S.Lorini, A.Luque-Escamilla, P.~L.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.Mas-Aguilar, A.Maurin, G.Mazin, D.Mestre Guillen, E.Micanovic, S.Miceli, D.Miener, T.Miranda, J.~M.Alvarez Crespo, N.Bhattacharjee, P.Buscemi, M.Freixas Coromina, L.Gliwny, P.Kataoka, J.Mirzoyan, R.Mizuno, T.Molero Gonzalez, M.Molina, E.Montaruli, T.Moralejo, A.Morcuende, D.Morselli, A.Muraishi, H.Nagataki, S.Nakamori, T.Artero, M.Baroncelli, L.Bernete Medrano, J.Cauz, D.Nickel, L.Nishijima, K.Noda, K.Nosek, D.Nozaki, S.Ohishi, M.Ohtani, Y.Oka, T.Okumura, A.Bernardos, M.~I.Biederbeck, N.Cornelia, A.Deleglise, G.Ferrara, G.Fukami, S.Garcia, E.Hashiyama, K.Hütten, M.Ishio, K.Jacquemont, M.Le Flour, T.Giro, E.Monteiro, I.Murase, K.Nievas, M.Orito, R.Otero-Santos, J.Palatiello, M.Paneque, D.Pantaleo, F.~R.Paoletti, R.Paredes, J.~M.Pech, M.Pecimotika, M.Peresano, M.
astroparticle physicsmethods: data analysisinstrumentation: high angular resolutiontechniques: high angular resolutiontechniques: image processingtelescopes
Date:
Nov 2023
Volume:
679
Number:
90
Journal:
aap
DOI:
10.1051/0004-6361/202347128
Citation Key:
2023A&A...679A..90A

Multiwavelength study of the galactic PeVatron candidate LHAASO J2108+5157

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 Γ = 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 Γ = 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.

Abe, S.Aguasca-Cabot, A.Agudo, I.Antonelli, L.~A.Aramo, C.Arbet-Engels, A.Asano, K.Aubert, P.Baktash, A.Bamba, A.Baquero Larriva, A.Barres de Almeida, U.Barrio, J.~A.Batkovic, I.Baxter, J.Becerra González, J.Bernardini, E.Berti, A.Bigongiari, C.Bissaldi, E.Blanch, O.Bordas, P.Bulgarelli, A.Burelli, I.Cardillo, M.Caroff, S.Carosi, A.Cassol, F.Ceribella, G.Chai, Y.Cheng, K.Chiavassa, A.Chikawa, M.Chytka, L.Cifuentes, A.Contreras, J.~L.Cortina, J.Costantini, H.Dalchenko, M.De Angelis, A.de Bony de Lavergne, M.Delgado, C.Delgado Mengual, J.Dellaiera, M.della Volpe, D.De Lotto, B.de Menezes, R.Díaz, C.Di Piano, A.Di Pierro, F.Di Tria, R.Di Venere, L.Dominik, R.~M.Dominis Prester, D.Donini, A.Dorner, D.Doro, M.Elsässer, D.Emery, G.Escudero, J.Fallah Ramazani, V.Fiasson, A.Fröse, S.Fukazawa, Y.Garcia López, R.Gasparrini, D.Geyer, D.Giesbrecht Paiva, J.Giglietto, N.Giordano, F.Godinovic, N.Grau, R.Green, D.Green, J.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.Imazawa, R.Inada, T.Inome, Y.Ioka, K.Iori, M.Jimenez Martinez, I.Jurysek, J.Kagaya, M.Karas, V.Katagiri, H.Kerszberg, D.Kobayashi, Y.Kong, A.Kubo, H.Kushida, J.Lainez, M.Lamanna, G.Lamastra, A.Linhoff, M.Longo, F.López-Coto, R.López-Moya, M.López-Oramas, A.Loporchio, S.Lorini, A.Luque-Escamilla, P.~L.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.Mas-Aguilar, A.Maurin, G.Mazin, D.Mestre Guillen, E.Micanovic, S.Miceli, D.Miener, T.Miranda, J.~M.Alvarez Crespo, N.Bhattacharjee, P.Buscemi, M.Freixas Coromina, L.Gliwny, P.Kataoka, J.Mirzoyan, R.Mizuno, T.Molero Gonzalez, M.Molina, E.Montaruli, T.Moralejo, A.Morcuende, D.Morselli, A.Nakamori, T.Artero, M.Baroncelli, L.Bernete Medrano, J.Cauz, D.Nickel, L.Nishijima, K.Noda, K.Nosek, D.Nozaki, S.Ohishi, M.Ohtani, Y.Okumura, A.Bernardos, M.~I.Biederbeck, N.D'Amico, G.Deleglise, G.Ferrara, G.Fukami, S.Garcia, E.Hashiyama, K.Hütten, M.Ishio, K.Jacquemont, M.Le Flour, T.Giro, E.Monteiro, I.Murase, K.Nievas, M.Orito, R.Otero-Santos, J.Palatiello, M.Paneque, D.Pantaleo, F.~R.Paoletti, R.Paredes, J.~M.Pech, M.Pecimotika, M.Iwamura, Y.Marusevec, P.Mrakovcic, K.Nagai, A.Okazaki, N.Buisson, C.Pavleti\'c, L.Pietropaolo, E.Pirola, G.Podobnik, F.Poireau, V.
pulsars: generalradiation mechanisms: non-thermalAstrophysics - High Energy Astrophysical Phenomenagamma rays: generalISM: individual objects: LHAASO J2108+5157
Date:
May 2023
Volume:
673
Number:
75
Journal:
aap
DOI:
10.1051/0004-6361/202245086
Eprint:
2210.00775
Citation Key:
2023A&A...673A..75A
Publication Repository

Performance of the joint LST-1 and MAGIC observations evaluated with Crab Nebula data

Aims: Large-Sized Telescope 1 (LST-1), the prototype for the Large-Sized Telescope at the upcoming Cherenkov Telescope Array Observatory, is concluding its commissioning phase at the Observatorio del Roque de los Muchachos on the island of La Palma. The proximity of LST-1 to the two MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes makes it possible to carry out observations of the same gamma-ray events with both systems. Methods: We describe the joint LST-1+MAGIC analysis pipeline and used simultaneous Crab Nebula observations and Monte Carlo simulations to assess the performance of the three-telescope system. The addition of the LST-1 telescope allows for the recovery of events in which one of the MAGIC images is too dim to survive analysis quality cuts. Results: Thanks to the resulting increase in the collection area and stronger background rejection, we found a significant improvement in sensitivity, allowing for the detection of 30% weaker fluxes in the energy range between 200 GeV and 3 TeV. The spectrum of the Crab Nebula, reconstructed in the energy range between ~60 GeV and ~10 TeV, is in agreement with previous measurements.

Abe, K.Abe, S.Aguasca-Cabot, A.Agudo, I.Antonelli, L.~A.Aramo, C.Arbet-Engels, A.Arcaro, C.Asano, K.Aubert, P.Baktash, A.Bamba, A.Baquero Larriva, A.Barres de Almeida, U.Barrio, J.~A.Baxter, J.Becerra González, J.Bernardini, E.Berti, A.Bigongiari, C.Bissaldi, E.Blanch, O.Bonnoli, G.Bordas, P.Bulgarelli, A.Burelli, I.Burmistrov, L.Cardillo, M.Caroff, S.Carosi, A.Carrasco, M.~S.Cassol, F.Cerasole, D.Ceribella, G.Chai, Y.Cheng, K.Chiavassa, A.Chikawa, M.Chytka, L.Cifuentes, A.Contreras, J.~L.Cortina, J.Costantini, H.Dalchenko, M.Da Vela, P.Dazzi, F.De Angelis, A.de Bony de Lavergne, M.Delgado Mengual, J.Dellaiera, M.della Volpe, D.De Lotto, B.Del Peral, L.de Menezes, R.Díaz, C.Di Piano, A.Di Pierro, F.Di Tria, R.Di Venere, L.Dominik, R.~M.Dominis Prester, D.Donini, A.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.Gasbarra, C.Gasparrini, D.Geyer, D.Giglietto, N.Giordano, F.Grau, R.Green, D.Gunji, S.Günther, P.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.Iarlori, M.Imazawa, R.Inada, T.Inome, Y.Ioka, K.Iori, M.Jimenez Martinez, I.Jurysek, J.Kagaya, M.Karas, V.Katagiri, H.Kerszberg, D.Kobayashi, Y.Kohri, K.Kong, A.Kubo, H.Kushida, J.Lainez, M.Lamanna, G.Lamastra, A.Linhoff, M.Lombardi, S.Longo, F.López-Coto, R.López-Moya, M.López-Oramas, A.Loporchio, S.Lorini, A.Lozano Bahilo, J.Luque-Escamilla, P.~L.Alvarez Crespo, N.Bhattacharjee, P.Buscemi, M.Freixas Coromina, L.Gliwny, P.Kataoka, J.Artero, M.Baroncelli, L.Bernete Medrano, J.Cauz, D.Abe, H.Acciari, V.~A.Aniello, T.Ansoldi, S.Baack, D.Babi\'c, A.Batkovi\'c, I.Bednarek, W.Bernardos, M.~I.Besenrieder, J.Biederbeck, N.Biland, A.Bo\vsnjak, \vZ.Busetto, G.Campoy Ordaz, A.Carosi, R.Carretero-Castrillo, M.Castro-Tirado, A.~J.Cikota, S.Colombo, E.Cornelia, A.Covino, S.D'Amico, G.D'Elia, V.De Lucia, M.Del Popolo, A.Deleglise, G.Delfino, M.Delgado Mendez, C.Depaoli, D.Di Pilato, A.Fariña, L.Fattorini, A.Ferrara, G.Font, L.Fukami, S.Garcia López, R.~J.Garcia, E.Garczarczyk, M.Gasparyan, S.Gaug, M.Giesbrecht Paiva, J.~G.Godinovi\'c, N.Green, J.~G.Hashiyama, K.Hütten, M.Iotov, R.Ishio, K.Jacquemont, M.Jobst, E.Jormanainen, J.Kluge, G.~W.Kouch, P.~M.Le Flour, T.Leone, F.Lindfors, E.Linhoff, L.Lyard, E.Láinez Lezáun, M.Machado de Oliveira Fraga, B.
Astrophysics - High Energy Astrophysical Phenomenainstrumentation: detectorsmethods: data analysisgamma rays: generalAstrophysics - Instrumentation and Methods for Astrophysics
Date:
Dec 2023
Volume:
680
Number:
66
Journal:
aap
DOI:
10.1051/0004-6361/202346927
Eprint:
2310.01954
Citation Key:
2023A&A...680A..66A
Publication Repository