Multi-wavelength study of the galactic PeVatron candidate LHAASO J2108+5157
Creators: name: Abe, S.
name: Aguasca-Cabot, A.
name: Agudo, I.
name: Crespo, N. Alvarez
name: Antonelli, L. A.
name: Aramo, C.
name: Arbet-Engels, A.
name: Artero, M.
name: Asano, K.
name: Aubert, P.
name: Baktash, A.
name: Bamba, A.
name: Larriva, A. Baquero
name: Baroncelli, L.
name: de Almeida, U. Barres
name: Barrio, J. A.
name: Batkovic, I.
name: Baxter, J.
name: González, J. Becerra
name: Bernardini, E.
name: Bernardos, M. I.
name: Medrano, J. Bernete
name: Berti, A.
name: Bhattacharjee, P.
name: Biederbeck, N.
name: Bigongiari, C.
name: Bissaldi, E.
name: Blanch, O.
name: Bordas, P.
name: Buisson, C.
name: Bulgarelli, A.
name: Burelli, I.
name: Buscemi, M.
name: Cardillo, M.
name: Caroff, S.
name: Carosi, A.
name: Cassol, F.
name: Cauz, D.
name: Ceribella, G.
name: Chai, Y.
name: Cheng, K.
name: Chiavassa, A.
name: Chikawa, M.
name: Chytka, L.
name: Cifuentes, A.
name: Contreras, J. L.
name: Cortina, J.
name: Costantini, H.
name: D'Amico, G.
name: Dalchenko, M.
name: De Angelis, A.
name: de Lavergne, M. de Bony
name: De Lotto, B.
name: de Menezes, R.
name: Deleglise, G.
name: Delgado, C.
name: Mengual, J. Delgado
name: della Volpe, D.
name: Dellaiera, M.
name: Di Piano, A.
name: Di Pierro, F.
name: Di Tria, R.
name: Di Venere, L.
name: Díaz, C.
name: Dominik, R. M.
name: Prester, D. Dominis
name: Donini, A.
name: Dorner, D.
name: Doro, M.
name: Elsässer, D.
name: Emery, G.
name: Escudero, J.
name: Ramazani, V. Fallah
name: Ferrara, G.
name: Fiasson, A.
name: Coromina, L. Freixas
name: Fröse, S.
name: Fukami, S.
name: Fukazawa, Y.
name: Garcia, E.
name: López, R. Garcia
name: Gasparrini, D.
name: Geyer, D.
name: Paiva, J. Giesbrecht
name: Giglietto, N.
name: Giordano, F.
name: Giro, E.
name: Gliwny, P.
name: Godinovic, N.
name: Grau, R.
name: Green, D.
name: Green, J.
name: Gunji, S.
name: Hackfeld, J.
name: Hadasch, D.
name: Hahn, A.
name: Hashiyama, K.
name: Hassan, T.
name: Hayashi, K.
name: Heckmann, L.
name: Heller, M.
name: Llorente, J. Herrera
name: Hirotani, K.
name: Hoffmann, D.
name: Horns, D.
name: Houles, J.
name: Hrabovsky, M.
name: Hrupec, D.
name: Hui, D.
name: Hütten, M.
name: Imazawa, R.
name: Inada, T.
name: Inome, Y.
name: Ioka, K.
name: Iori, M.
name: Ishio, K.
name: Iwamura, Y.
name: Jacquemont, M.
name: Martinez, I. Jimenez
name: Jurysek, J.
name: Kagaya, M.
name: Karas, V.
name: Katagiri, H.
name: Kataoka, J.
name: Kerszberg, D.
name: Kobayashi, Y.
name: Kong, A.
name: Kubo, H.
name: Kushida, J.
name: Lainez, M.
name: Lamanna, G.
name: Lamastra, A.
name: Flour, T. Le
name: Linhoff, M.
name: Longo, F.
name: López-Coto, R.
name: López-Moya, M.
name: López-Oramas, A.
name: Loporchio, S.
name: Lorini, A.
name: Luque-Escamilla, P. L.
name: Majumdar, P.
name: Makariev, M.
name: Mandat, D.
name: Manganaro, M.
name: Manicò, G.
name: Mannheim, K.
name: Mariotti, M.
name: Marquez, P.
name: Marsella, G.
name: Martí, J.
name: Martinez, O.
name: Martínez, G.
name: Martínez, M.
name: Marusevec, P.
name: Mas-Aguilar, A.
name: Maurin, G.
name: Mazin, D.
name: Guillen, E. Mestre
name: Micanovic, S.
name: Miceli, D.
name: Miener, T.
name: Miranda, J. M.
name: Mirzoyan, R.
name: Mizuno, T.
name: Gonzalez, M. Molero
name: Molina, E.
name: Montaruli, T.
name: Monteiro, I.
name: Moralejo, A.
name: Morcuende, D.
name: Morselli, A.
name: Mrakovcic, K.
name: Murase, K.
name: Nagai, A.
name: Nakamori, T.
name: Nickel, L.
name: Nievas, M.
name: Nishijima, K.
name: Noda, K.
name: Nosek, D.
name: Nozaki, S.
name: Ohishi, M.
name: Ohtani, Y.
name: Okazaki, N.
name: Okumura, A.
name: Orito, R.
name: Otero-Santos, J.
name: Palatiello, M.
name: Paneque, D.
name: Pantaleo, F. R.
name: Paoletti, R.
name: Paredes, J. M.
name: Pavletić, L.
name: Pech, M.
name: Pecimotika, M.
name: Pietropaolo, E.
name: Pirola, G.
name: Podobnik, F.
name: Poireau, V.
name: Polo, M.
name: Pons, E.
name: Prandini, E.
name: Prast, J.
name: Priyadarshi, C.
name: Prouza, M.
name: Rando, R.
name: Rhode, W.
name: Ribó, M.
name: Rizi, V.
name: Fernandez, G. Rodriguez
name: Saito, T.
name: Sakurai, S.
name: Sanchez, D. A.
name: Šarić, T.
name: Saturni, F. G.
name: Scherpenberg, J.
name: Schleicher, B.
name: Schmuckermaier, F.
name: Schubert, J. L.
name: Schussler, F.
name: Schweizer, T.
name: Arroyo, M. Seglar
name: Sitarek, J.
name: Sliusar, V.
name: Spolon, A.
name: Strišković, J.
name: Strzys, M.
name: Suda, Y.
name: Sunada, Y.
name: Tajima, H.
name: Takahashi, M.
name: Takahashi, H.
name: Takata, J.
name: Takeishi, R.
name: Tam, P. H. T.
name: Tanaka, S. J.
name: Tateishi, D.
name: Temnikov, P.
name: Terada, Y.
name: Terauchi, K.
name: Terzic, T.
name: Teshima, M.
name: Tluczykont, M.
name: Tokanai, F.
name: Torres, D. F.
name: Travnicek, P.
name: Truzzi, S.
name: Tutone, A.
name: Uhlrich, G.
name: Vacula, M.
name: Acosta, M. Vázquez
name: Verguilov, V.
name: Viale, I.
name: Vigliano, A.
name: Vigorito, C. F.
name: Vitale, V.
name: Voutsinas, G.
name: Vovk, I.
name: Vuillaume, T.
name: Walter, R.
name: Will, M.
name: Yamamoto, T.
name: Yamazaki, R.
name: Yoshida, T.
name: Yoshikoshi, T.
name: Zywucka, N.
name: Balbo, M.
name: Eckert, D.
name: Tramacere, A.
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: LHAASO J2108+5157 is one of the few known unidentified Ultra-High-Energy (UHE) gamma-ray sources with no Very-High-Energy (VHE) counterpart, recently discovered by the LHAASO collaboration. 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 found an excess (3.7 sigma) in the LST-1 data at energies E &gt; 3 TeV. Further analysis in the whole LST-1 energy range assuming a point-like source, resulted in a hint (2.2 sigma) of hard emission which can be described with a single power law with photon index Gamma = 1.6 +- 0.2 between 0.3 - 100 TeV. We did not find any significant extended emission which 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. The LST-1 and LHAASO observations can be explained as inverse Compton-dominated leptonic emission of relativistic electrons with a cutoff energy of $100^{+70}_{-30}$ 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. The lack of a pulsar in the neighborhood of the UHE source is a challenge to the PWN/TeV-halo scenario. The UHE gamma rays can also be explained as $π^0$ decay-dominated hadronic emission due to interaction of relativistic protons with one of the two known molecular clouds in the direction of the source. 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.
description: 26 pages, 9 figures, 5 tables; Astronomy and Astrophysics (accepted on 6 March 2023)