Naslov
Multiwavelength study of the galactic PeVatron candidate LHAASO J2108+5157

Autori
Abe, S. ; Aguasca-Cabot, A. ; Agudo, I. ; Alvarez Crespo, N. ; Antonelli, L. A. ; Aramo, C. ; Arbet- Engels, A. ; Artero, M. ; Asano, K. ; Aubert, P. ; Baktash, A. ; Bamba, A. ; Baquero Larriva, A. ; Baroncelli, L. ; Barres de Almeida, U. ; Barrio, J. A. ; Batkovic, I. ; Baxter, J. ; Becerra González, J. ; Bernardini, E. ; Bernardos, M. I. ; Bernete Medrano, J. ; 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, J. L. ; Cortina, J. ; Costantini, H. ; D’Amico, G. ; Dalchenko, M. ; De Angelis, A. ; de Bony de Lavergne, M. ; De Lotto, B. ; de Menezes, R. ; Deleglise, G. ; 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. ; Dorner, D. ; Doro, M. ; Elsässer, D. ; Emery, G. ; Escudero, J. ; Fallah Ramazani, V. ; Ferrara, G. ; Fiasson, A. ; Freixas Coromina, L. ; Fröse, S. ; Fukami, S. ; Fukazawa, Y. ; Garcia, E. ; Garcia López, R. ; Gasparrini, D. ; Geyer, D. ; Giesbrecht Paiva, J. ; 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. ; Herrera Llorente, J. ; 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. ; Jimenez Martinez, I. ; 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, 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. ; Marusevec, P. ; Mas-Aguilar, A. ; Maurin, G. ; Mazin, D. ; Mestre Guillen, E. ; Micanovic, S. ; Miceli, D. ; Miener, T. ; Miranda, J. M. ; Mirzoyan, R. ; Mizuno, T. ; Molero Gonzalez, M. ; 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, F. R. ; Paoletti, R. ; Paredes, J. M. ; Pavletić, 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. ; Rodriguez Fernandez, G. ; Saito, T. ; Sakurai, S. ; Sanchez, D. A. ; Šarić, T. ; Saturni, F. G. ; Scherpenberg, J. ; Schleicher, B. ; Schmuckermaier, F. ; Schubert, J. L. ; Schussler, F. ; Schweizer, T. ; Seglar Arroyo, M. ; Sitarek, J. ; Sliusar, V. ; Spolon, A. ; Strišković, J. ; Strzys, M. ; Suda, Y. ; Sunada, Y. ; Tajima, H. ; Takahashi, M. ; Takahashi, H. ; Takata, J. ; Takeishi, R. ; Tam, P. H. T. ; Tanaka, S. J. ; Tateishi, D. ; Temnikov, P. ; Terada, Y. ; Terauchi, K. ; Terzic, T. ; Teshima, M. ; Tluczykont, M. ; Tokanai, F. ; Torres, D. F. ; Travnicek, P. ; Truzzi, S. ; Tutone, A. ; Uhlrich, G. ; Vacula, M. ; Vázquez Acosta, M. ; Verguilov, V. ; Viale, I. ; Vigliano, A. ; Vigorito, C. F. ; Vitale, V. ; Voutsinas, G. ; Vovk, I. ; Vuillaume, T. ; Walter, R. ; Will, M. ; Yamamoto, T. ; Yamazaki, R. ; Yoshida, T. ; Yoshikoshi, T. ; Zywucka (CTA-LST Project), N. ; Balbo, M. ; Eckert, D. ; Tramacere, A.

Kolaboracija
Large-Sized Telescope Collaboration

Izvornik
Astronomy & astrophysics (0004-6361) 673 (2023); A75, 16

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Large-Sized Telescope ; LHAASO J2108+5157

Sažetak
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+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. 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 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. 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.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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