Multi-wavelength study of the galactic PeVatron candidate LHAASO J2108+5157
Abstract
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 > 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 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 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.
Keywords
Cite
@article{arxiv.2210.00775,
title = {Multi-wavelength study of the galactic PeVatron candidate LHAASO J2108+5157},
author = {S. Abe and A. Aguasca-Cabot and I. Agudo and N. Alvarez Crespo and L. A. Antonelli and C. Aramo and A. Arbet-Engels and M. Artero and K. Asano and P. Aubert and A. Baktash and A. Bamba and A. Baquero Larriva and L. Baroncelli and U. Barres de Almeida and J. A. Barrio and I. Batkovic and J. Baxter and J. Becerra González and E. Bernardini and M. I. Bernardos and J. Bernete Medrano and A. Berti and P. Bhattacharjee and N. Biederbeck and C. Bigongiari and E. Bissaldi and O. Blanch and P. Bordas and C. Buisson and A. Bulgarelli and I. Burelli and M. Buscemi and M. Cardillo and S. Caroff and A. Carosi and F. Cassol and D. Cauz and G. Ceribella and Y. Chai and K. Cheng and A. Chiavassa and M. Chikawa and L. Chytka and A. Cifuentes and J. L. Contreras and J. Cortina and H. Costantini and G. D'Amico and M. Dalchenko and A. De Angelis and M. de Bony de Lavergne and B. De Lotto and R. de Menezes and G. Deleglise and C. Delgado and J. Delgado Mengual and D. della Volpe and M. Dellaiera and A. Di Piano and F. Di Pierro and R. Di Tria and L. Di Venere and C. Díaz and R. M. Dominik and D. Dominis Prester and A. Donini and D. Dorner and M. Doro and D. Elsässer and G. Emery and J. Escudero and V. Fallah Ramazani and G. Ferrara and A. Fiasson and L. Freixas Coromina and S. Fröse and S. Fukami and Y. Fukazawa and E. Garcia and R. Garcia López and D. Gasparrini and D. Geyer and J. Giesbrecht Paiva and N. Giglietto and F. Giordano and E. Giro and P. Gliwny and N. Godinovic and R. Grau and D. Green and J. Green and S. Gunji and J. Hackfeld and D. Hadasch and A. Hahn and K. Hashiyama and T. Hassan and K. Hayashi and L. Heckmann and M. Heller and J. Herrera Llorente and K. Hirotani and D. Hoffmann and D. Horns and J. Houles and M. Hrabovsky and D. Hrupec and D. Hui and M. Hütten and R. Imazawa and T. Inada and Y. Inome and K. Ioka and M. Iori and K. Ishio and Y. Iwamura and M. Jacquemont and I. Jimenez Martinez and J. Jurysek and M. Kagaya and V. Karas and H. Katagiri and J. Kataoka and D. Kerszberg and Y. Kobayashi and A. Kong and H. Kubo and J. Kushida and M. Lainez and G. Lamanna and A. Lamastra and T. Le Flour and M. Linhoff and F. Longo and R. López-Coto and M. López-Moya and A. López-Oramas and S. Loporchio and A. Lorini and P. L. Luque-Escamilla and P. Majumdar and M. Makariev and D. Mandat and M. Manganaro and G. Manicò and K. Mannheim and M. Mariotti and P. Marquez and G. Marsella and J. Martí and O. Martinez and G. Martínez and M. Martínez and P. Marusevec and A. Mas-Aguilar and G. Maurin and D. Mazin and E. Mestre Guillen and S. Micanovic and D. Miceli and T. Miener and J. M. Miranda and R. Mirzoyan and T. Mizuno and M. Molero Gonzalez and E. Molina and T. Montaruli and I. Monteiro and A. Moralejo and D. Morcuende and A. Morselli and K. Mrakovcic and K. Murase and A. Nagai and T. Nakamori and L. Nickel and M. Nievas and K. Nishijima and K. Noda and D. Nosek and S. Nozaki and M. Ohishi and Y. Ohtani and N. Okazaki and A. Okumura and R. Orito and J. Otero-Santos and M. Palatiello and D. Paneque and F. R. Pantaleo and R. Paoletti and J. M. Paredes and L. Pavletić and M. Pech and M. Pecimotika and E. Pietropaolo and G. Pirola and F. Podobnik and V. Poireau and M. Polo and E. Pons and E. Prandini and J. Prast and C. Priyadarshi and M. Prouza and R. Rando and W. Rhode and M. Ribó and V. Rizi and G. Rodriguez Fernandez and T. Saito and S. Sakurai and D. A. Sanchez and T. Šarić and F. G. Saturni and J. Scherpenberg and B. Schleicher and F. Schmuckermaier and J. L. Schubert and F. Schussler and T. Schweizer and M. Seglar Arroyo and J. Sitarek and V. Sliusar and A. Spolon and J. Strišković and M. Strzys and Y. Suda and Y. Sunada and H. Tajima and M. Takahashi and H. Takahashi and J. Takata and R. Takeishi and P. H. T. Tam and S. J. Tanaka and D. Tateishi and P. Temnikov and Y. Terada and K. Terauchi and T. Terzic and M. Teshima and M. Tluczykont and F. Tokanai and D. F. Torres and P. Travnicek and S. Truzzi and A. Tutone and G. Uhlrich and M. Vacula and M. Vázquez Acosta and V. Verguilov and I. Viale and A. Vigliano and C. F. Vigorito and V. Vitale and G. Voutsinas and I. Vovk and T. Vuillaume and R. Walter and M. Will and T. Yamamoto and R. Yamazaki and T. Yoshida and T. Yoshikoshi and N. Zywucka and M. Balbo and D. Eckert and A. Tramacere},
journal= {arXiv preprint arXiv:2210.00775},
year = {2023}
}
Comments
26 pages, 9 figures, 5 tables; Astronomy and Astrophysics (accepted on 6 March 2023)