Bibcode
Abe, K.; Abe, S.; Abhishek, A.; Acero, F.; Aguasca-Cabot, A.; Agudo, I.; Alispach, C.; Alvarez Crespo, N.; 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.; Bhattacharjee, P.; Bigongiari, C.; Bissaldi, E.; Blanch, O.; Bonnoli, G.; Bordas, P.; Borkowski, G.; Brunelli, G.; Bulgarelli, A.; Bunse, M.; Burelli, I.; Burmistrov, L.; Buscemi, M.; 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.; Da Vela, P.; Dalchenko, M.; Dazzi, F.; De Angelis, A.; de Bony de Lavergne, M.; De Lotto, B.; de Menezes, R.; Del Burgo, R.; Del Peral, L.; Delgado, C.; Delgado Mengual, J.; della Volpe, D.; Dellaiera, M.; Di Piano, A.; Di Pierro, F.; Di Tria, R.; Di Venere, L.; Díaz, C.; 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.; Freixas Coromina, L.; Fröse, S.; Fukazawa, Y.; Garcia López, R.; Gasbarra, C.; Gasparrini, D.; Geyer, D. et al.
Bibliographical reference
Astronomy and Astrophysics
Advertised on:
3
2025
Journal
Citations
0
Refereed citations
0
Description
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.