Multi-year characterisation of the broad-band emission from the intermittent extreme BL Lac 1ES 2344+514
: Abe, H.; Abe, S.; Acciari, V.; Agudo, I.; Aniello, T.; Ansoldi, S.; Antonelli, L.; Arbet Engels, A.; Arcaro, C.; Artero, M.; Asano, K.; Baack, D.; Babić, A.; Baquero, A.; Barres De Almeida, U.; Batković, I.; Baxter, J.; Becerra González, J.; Bernardini, E.; Bernete, J.; Berti, A.; Besenrieder, J.; Bigongiari, C.; Biland, A.; Blanch, O.; Bonnoli, G.; Bošnjak, Ž.; Burelli, I.; Busetto, G.; Campoy-Ordaz, A.; Carosi, A.; Carosi, R.; Carretero-Castrillo, M.; Castro-Tirado, A.; Chai, Y.; Cifuentes, A.; Cikota, S.; Colombo, E.; Contreras, J.; Cortina, J.; Covino, S.; D'Amico, G.; D'Ammando, F.; D'Elia, V.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Del Popolo, A.; Delfino, M.; Delgado, J.; Delgado Mendez, C.; Depaoli, D.; Di Pierro, F.; Di Venere, L.; Dominis Prester, D.; Dorner, D.; Doro, M.; Elsaesser, D.; Emery, G.; Escudero, J.; Fariña, L.; Fattorini, A.; Foffano, L.; Font, L.; Fukami, S.; Fukazawa, Y.; García López, R.; Gasparyan, S.; Gaug, M.; Giesbrecht Paiva, J.; Giglietto, N.; Giordano, F.; Gliwny, P.; Grau, R.; Green, J.; Hadasch, D.; Hahn, A.; Heckmann, L.; Herrera, J.; Hrupec, D.; Hütten, M.; Imazawa, R.; Inada, T.; Iotov, R.; Ishio, K.; Jiménez Martínez, I.; Jormanainen, J.; Kerszberg, D.; Kluge, G.; Kobayashi, Y.; Kouch, P.; Kubo, H.; Kushida, J.; Láinez Lezáun, M.; Lamastra, A.; Leone, F.; Lindfors, E.; Linhoff, L.; Lombardi, S.; Longo, F.; López-Moya, M.; López-Oramas, A.; Loporchio, S.; Lorini, A.; MacHado De Oliveira Fraga, B.; Majumdar, P.; Makariev, M.; Maneva, G.; Mang, N.; Manganaro, M.; Mariotti, M.; Martínez, M.; Martínez-Chicharro, M.; Mas-Aguilar, A.; Mazin, D.; Menchiari, S.; Mender, S.; Miceli, D.; Miener, T.; Miranda, J.; Mirzoyan, R.; Molero González, M.; Molina, E.; Mondal, H.; Moralejo, A.; Morcuende, D.; Nakamori, T.; Nanci, C.; Neustroev, V.; Nigro, C.; Nikolić, L.; Nishijima, K.; Njoh Ekoume, T.; Noda, K.; Nozaki, S.; Ohtani, Y.; Okumura, A.; Otero-Santos, J.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J.; Pavlović, D.; Persic, M.; Pihet, M.; Pirola, G.; Podobnik, F.; Prada Moroni, P.; Prandini, E.; Principe, G.; Priyadarshi, C.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Sahakyan, N.; Saito, T.; Satalecka, K.; Saturni, F.; Schleicher, B.; Schmidt, K.; Schmuckermaier, F.; Schubert, J.; Schweizer, T.; Sciaccaluga, A.; Sitarek, J.; Spolon, A.; Stamerra, A.; Strišković, J.; Strom, D.; Suda, Y.; Tajima, H.; Takeishi, R.; Tavecchio, F.; Temnikov, P.; Terauchi, K.; Terzić, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone, A.; Ubach, S.; Van Scherpenberg, J.; Ventura, S.; Verguilov, V.; Viale, I.; Vigorito, C.; Vitale, V.; Walter, R.; Wunderlich, C.; Yamamoto, T.; Perri, M.; Verrecchia, F.; Leto, C.; Das, S.; Chatterjee, R.; Raiteri, C.; Villata, M.; Semkov, E.; Ibryamov, S.; Bachev, R.; Strigachev, A.; Damljanovic, G.; Vince, O.; Jovanovic, M.; Stojanovic, M.; Larionov, V.; Grishina, T.; Kopatskaya, E.; Larionova, E.; Morozova, D.; Savchenko, S.; Troitskiy, I.; Troitskaya, Y.; Vasilyev, A.; Chen, W.; Hou, W.; Lin, C.; Tsai, A.; Jorstad, S.; Weaver, Z.; Acosta-Pulido, J.; Carnerero, M.; Carosati, D.; Kurtanidze, S.; Kurtanidze, O.; Jordan, B.; Ivanidze, R.; Gazeas, K.; Vrontaki, K.; Hovatta, T.; Liodakis, I.; Readhead, A.; Kiehlmann, S.; Zheng, W.; Filippenko, A.; Fallah Ramazani, V.
Publisher: EDP Sciences
: 2024
Astronomy and Astrophysics
: Astronomy and Astrophysics
: A114
: 682
: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202347845
: https://www.aanda.org/articles/aa/full_html/2024/02/aa47845-23/aa47845-23.html
: https://research.utu.fi/converis/portal/detail/Publication/387309370
: https://arxiv.org/abs/2310.03922
Aims.
The BL Lac 1ES 2344+514 is known for temporary extreme properties characterised by a shift of the synchrotron spectral energy distribution (SED) peak energy νsynch,p above 1 keV. While those extreme states have only been observed during high flux levels thus far, additional multi-year observing campaigns are required to achieve a coherent picture. Here, we report the longest investigation of the source from radio to very high energy (VHE) performed so far, focussing on a systematic characterisation of the intermittent extreme states.
Methods.
We organised a monitoring campaign covering a 3-year period from 2019 to 2021. More than ten instruments participated in the observations in order to cover the emission from radio to VHE. In particular, sensitive X-ray measurements by XMM-Newton, NuSTAR, and AstroSat took place simultaneously with multi-hour MAGIC observations, providing an unprecedented constraint of the two SED components for this blazar.
Results.
While our results confirm that 1ES 2344+514 typically exhibits νsynch,p > 1 keV 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 in the electron acceleration efficiency without a change in the electron injection luminosity. On the other hand, we also report a strong X-ray flare (among the brightest for 1ES 2344+514) without a significant shift of νsynch,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. By combining Swift-XRT and Swift-UVOT measurements 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 significantly contribute 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 0.3-2 keV band. Using time-dependent leptonic modelling, we show that this behaviour, in contradiction to single-zone scenarios, can instead be explained by a two-component model. © The Authors 2024.
