Multi-year characterisation of the broad-band emission from the intermittent extreme BL Lac 1ES~2344+514
Creators: name: Abe, H.
name: Abe, S.
name: Acciari, V. A.
name: Agudo, I.
name: Aniello, T.
name: Ansoldi, S.
name: Antonelli, L. A.
name: Engels, A. Arbet
name: Arcaro, C.
name: Artero, M.
name: Asano, K.
name: Baack, D.
name: Babić, A.
name: Baquero, A.
name: de Almeida, U. Barres
name: Batković, I.
name: Baxter, J.
name: González, J. Becerra
name: Bernardini, E.
name: Bernete, J.
name: Berti, A.
name: Besenrieder, J.
name: Bigongiari, C.
name: Biland, A.
name: Blanch, O.
name: Bonnoli, G.
name: Bošjak, Ž
name: Burelli, I.
name: Busetto, G.
name: Campoy-Ordaz, A.
name: Carosi, A.
name: Carosi, R.
name: Carretero-Castrillo, M.
name: Castro-Tirado, A. J.
name: Chai, Y.
name: Cifuentes, A.
name: Cikota, S.
name: Colombo, E.
name: Contreras, J. L.
name: Cortina, J.
name: Covino, S.
name: D'Amico, G.
name: D'Ammando, F.
name: D'Elia, V.
name: Da Vela, P.
name: Dazzi, F.
name: De Angelis, A.
name: De Lotto, B.
name: Del Popolo, A.
name: Delfino, M.
name: Delgado, J.
name: Mendez, C. Delgado
name: Depaoli, D.
name: Di Pierro, F.
name: Di Venere, L.
name: Prester, D. Dominis
name: Dorner, D.
name: Doro, M.
name: Elsaesser, D.
name: Emery, G.
name: Escudero, J.
name: Fariña, L.
name: Fattorini, A.
name: Foffano, L.
name: Font, L.
name: Fukami, S.
name: Fukazawa, Y.
name: López, R. J. García
name: Gasparyan, S.
name: Gaug, M.
name: Paiva, J. G. Giesbrecht
name: Giglietto, N.
name: Giordano, F.
name: Gliwny, P.
name: Grau, R.
name: Green, J. G.
name: Hadasch, D.
name: Hahn, A.
name: Heckmann, L.
name: Herrera, J.
name: Hrupec, D.
name: Hütten, M.
name: Imazawa, R.
name: Inada, T.
name: Iotov, R.
name: Ishio, K.
name: Martínez, I. Jiménez
name: Jormanainen, J.
name: Kerszberg, D.
name: Kluge, G. W.
name: Kobayashi, Y.
name: Kouch, P. M.
name: Kubo, H.
name: Kushida, J.
name: Lezáun, M. Láinez
name: Lamastra, A.
name: Leone, F.
name: Lindfors, E.
name: Linhoff, L.
name: Lombardi, S.
name: Longo, F.
name: López-Moya, M.
name: López-Oramas, A.
name: Loporchio, S.
name: Lorini, A.
name: Fraga, B. Machado de Oliveira
name: Majumdar, P.
name: Makariev, M.
name: Maneva, G.
name: Mang, N.
name: Manganaro, M.
name: Mariotti, M.
name: Martínez, M.
name: Martínez-Chicharro, M.
name: Mas-Aguilar, A.
name: Mazin, D.
name: Menchiari, S.
name: Mender, S.
name: Miceli, D.
name: Miener, T.
name: Miranda, J. M.
name: Mirzoyan, R.
name: González, M. Molero
name: Molina, E.
name: Mondal, H. A.
name: Moralejo, A.
name: Morcuende, D.
name: Nakamori, T.
name: Nanci, C.
name: Neustroev, V.
name: Nigro, C.
name: Nikolić, L.
name: Nishijima, K.
name: Ekoume, T. Njoh
name: Noda, K.
name: Nozaki, S.
name: Ohtani, Y.
name: Okumura, A.
name: Otero-Santos, J.
name: Paiano, S.
name: Palatiello, M.
name: Paneque, D.
name: Paoletti, R.
name: Paredes, J. M.
name: Pavlović, D.
name: Persic, M.
name: Pihet, M.
name: Pirola, G.
name: Podobnik, F.
name: Moroni, P. G. Prada
name: Prandini, E.
name: Principe, G.
name: Priyadarshi, C.
name: Rhode, W.
name: Ribó, M.
name: Rico, J.
name: Righi, C.
name: Sahakyan, N.
name: Saito, T.
name: Satalecka, K.
name: Saturni, F. G.
name: Schleicher, B.
name: Schmidt, K.
name: Schmuckermaier, F.
name: Schubert, J. L.
name: Schweizer, T.
name: Sciaccaluga, A.
name: Sitarek, J.
name: Spolon, A.
name: Stamerra, A.
name: Strišović, J.
name: Strom, D.
name: Suda, Y.
name: Tajima, H.
name: Takeishi, R.
name: Tavecchio, F.
name: Temnikov, P.
name: Terauchi, K.
name: Terzić, T.
name: Teshima, M.
name: Tosti, L.
name: Truzzi, S.
name: Tutone, A.
name: Ubach, S.
name: van Scherpenberg, J.
name: Ventura, S.
name: Verguilov, V.
name: Viale, I.
name: Vigorito, C. F.
name: Vitale, V.
name: Walter, R.
name: Wunderlich, C.
name: Leto, T. Yamamoto M. Perri F. Verrecchia C.
name: Das, S.
name: Chatterjee, R.
name: Raiteri, C. M.
name: Villata, M.
name: Semkov, E.
name: Ibryamov, S.
name: Bachev, R.
name: Strigachev, A.
name: Damljanovic, G.
name: Vince, O.
name: Jovanovic, M. D.
name: Stojanovic, M.
name: Larionov, V. M.
name: Grishina, T. S.
name: Kopatskaya, E. N.
name: Larionova, E. G.
name: Morozova, D. A.
name: Savchenko, S. S.
name: Troitskiy, I. S.
name: Troitskaya, Y. V.
name: Vasilyev, A. A.
name: Chen, W. P.
name: Hou, W. J.
name: Lin, C. S.
name: Tsai, A.
name: Jorstad, S. G.
name: Weaver, Z. R.
name: Acosta-Pulido, J. A.
name: Carnerero, M. I.
name: Carosati, D.
name: Kurtanidze, S. O.
name: Kurtanidze, O. M.
name: Jordan, B.
name: Ivanidze, R. Z.
name: Gazeas, K.
name: Vrontaki, K.
name: Hovatta, T.
name: Liodakis, I.
name: Readhead, A. C. S.
name: Kiehlmann, S.
name: Zheng, W.
name: Filippenko, A. V.
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: The BL Lac 1ES 2344+514 is known for temporary extreme properties (e.g., a shift of the synchrotron SED peak energy $ν_{synch,p}$ above 1keV). While those extreme states were so far observed only during high flux levels, additional multi-year observing campaigns are required to achieve a coherent picture. Here, we report the longest investigation of the source from radio to VHE performed so far, focusing on a systematic characterisation of the intermittent extreme states. While our results confirm that 1ES 2344+514 typically exhibits $ν_{synch,p}&gt;$1keV during elevated flux periods, we also find periods where the extreme state coincides with low flux activity. A strong spectral variability thus happens in the quiescent state, and is likely caused by an increase of the electron acceleration efficiency without a change in the electron injection luminosity. We also report a strong X-ray flare (among the brightest for 1ES 2344+514) without a significant shift of $ν_{synch,p}$. During this particular flare, the X-ray spectrum is among the softest of the campaign. It unveils complexity in the spectral evolution, where the common harder-when-brighter trend observed in BL Lacs is violated. During a low and hard X-ray state, we find an excess of the UV flux with respect to an extrapolation of the X-ray spectrum to lower energies. This UV excess implies that at least two regions contribute significantly to the infrared/optical/ultraviolet/X-ray emission. Using the simultaneous MAGIC, XMM-Newton, NuSTAR, and AstroSat observations, we argue that a region possibly associated with the 10 GHz radio core may explain such an excess. Finally, we investigate a VHE flare, showing an absence of simultaneous variability in the 0.3-2keV band. Using a time-dependent leptonic modelling, we show that this behaviour, in contradiction to single-zone scenarios, can instead be explained by a two-component model.
description: Accepted for publication in Astronomy &amp; Astrophysics