Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Articles Article Faculty Publications -Articles Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Extreme photometric and polarimetric variability of blazar S4 0954+65 at its maximum optical and ?-ray brightness levels Subject The topic of the resource BL Lacertae objects: general; BL Lacertae objects: individual: S4 0954+65; galaxies: active; galaxies: jets Description An account of the resource In 2022 the BL Lac object S4 0954+65 underwent a major variability phase, reaching its historical maximum brightness in the optical and ?-ray bands. We present optical photometric and polarimetric data acquired by the Whole Earth Blazar Telescope (WEBT) Collaboration from 2022 April 6 to July 6. Many episodes of unprecedented fast variability were detected, implying an upper limit to the size of the emitting region as low as parsec. The WEBT data show rapid variability in both the degree and angle of polarization. We analyse different models to explain the polarization behaviour in the framework of a twisting jet model, which assumes that the long-term trend of the flux is produced by variations in the emitting region viewing angle. All the models can reproduce the average trend of the polarization degree, and can account for its general anticorrelation with the flux, but the dispersion of the data requires the presence of intrinsic mechanisms, such as turbulence, shocks, or magnetic reconnection. The WEBT optical data are compared to ?-ray data from the Fermi satellite. These are analysed with both fixed and adaptive binning procedures. We show that the strong correlation between optical and ?-ray data without measurable delay assumes different slopes in faint and high brightness states, and this is compatible with a scenario where in faint states we mainly see the imprint of the geometrical effects, while in bright states the synchrotron self-Compton process dominates. 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. Creator An entity primarily responsible for making the resource Raiteri C.M.; Villata M.; Carnerero M.I.; Savchenko S.S.; Kurtanidze S.O.; Vlasyuk V.V.; Marchini A.; Matsumoto K.; Lorey C.; Joner M.D.; Gazeas K.; Carosati D.; Mirzaqulov D.O.; Acosta Pulido J.A.; Agudo I.; Bachev R.; Benez E.; Borman G.A.; Calcidese P.; Chen W.P.; Damljanovic G.; Ehgamberdiev S.A.; Elsser D.; Feige M.; Frasca A.; Gaur H.; Grishina T.S.; Gupta A.C.; Hiriart D.; Holland M.; Horst B.; Ibryamov S.; Ivanidze R.Z.; Jensen J.; Jithesh V.; Jovanovic M.D.; Kiehlmann S.; Kimeridze G.N.; Kishore S.; Kopatskaya E.N.; Kurtanidze O.M.; Larionova E.G.; Lin H.C.; Mannheim K.; Marinelli C.; Moreira Reyes J.; Morozova D.A.; Nikolashvili M.G.; Reinhart D.; Romanov F.D.; Semkov E.; Seufert J.; Shishkina E.V.; Sigua L.A.; Skalidis R.; Spiridonova O.I.; Stojanovic M.; Strigachev A.; Troitskaya Y.V.; Troitskiy I.S.; Tsai A.; Vasilyev A.A.; Vince O.; Vrontaki K.; Wani K.; Watts D.; Zhovtan A.V. Source A related resource from which the described resource is derived Monthly Notices of the Royal Astronomical Society, Vol-526, No. 3, pp. 4502-4513. Publisher An entity responsible for making the resource available Oxford University Press Date A point or period of time associated with an event in the lifecycle of the resource 2023-01-01 Identifier An unambiguous reference to the resource within a given context <a href="https://doi.org/10.1093/mnras/stad3064" target="_blank" rel="noreferrer noopener">https://doi.org/10.1093/mnras/stad3064</a> <br /><br /><a href="https://www.scopus.com/inward/record.uri?eid=2-s2.0-85175616458&amp;doi=10.1093%2Fmnras%2Fstad3064&amp;partnerID=40&amp;md5=ff3a5f13eeb265cc3a2cf7e87ce41868" target="_blank" rel="noreferrer noopener">https://www.scopus.com/inward/record.uri?eid=2-s2.0-85175616458&amp;doi=10.1093%2fmnras%2fstad3064&amp;partnerID=40&amp;md5=ff3a5f13eeb265cc3a2cf7e87ce41868</a> Rights Information about rights held in and over the resource All Open Access; Green Open Access; Hybrid Gold Open Access Relation A related resource ISSN: 358711; CODEN: MNRAA Format The file format, physical medium, or dimensions of the resource Online Language A language of the resource English Type The nature or genre of the resource Article Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Raiteri C.M., Inaf, Osservatorio Astrofisico di Torino, via Osservatorio 20, Pino Torinese, I-10025, Italy; Villata M., Inaf, Osservatorio Astrofisico di Torino, via Osservatorio 20, Pino Torinese, I-10025, Italy; Carnerero M.I., Inaf, Osservatorio Astrofisico di Torino, via Osservatorio 20, Pino Torinese, I-10025, Italy; Savchenko S.S., Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russian Federation, Special Astrophysical Observatory of Russian Academy of Sciences, Nyzhnij Arkhyz,Circassia,Karachai, 369167, Russian Federation, Pulkovo Observatory, St. Petersburg, 196140, Russian Federation; Kurtanidze S.O., Abastumani Observatory, Mt. Kanobili, Abastumani, 0301, Georgia; Vlasyuk V.V., Special Astrophysical Observatory of Russian Academy of Sciences, Nyzhnij Arkhyz,Circassia,Karachai, 369167, Russian Federation; Marchini A., Astronomical Observatory, University of Siena, Siena, I-53100, Italy; Matsumoto K., Astronomical Institute, Osaka Kyoiku University, Osaka, 582-8582, Japan; Lorey C., Hans-Haffner-Sternwarte (Hettstadt), Naturwissenschaftliches Labor f Scher, Friedrich-Koenig-Gymnasium, Wzburg, D-97082, Germany; Joner M.D., Department of Physics and Astronomy, N283 Esc, Brigham Young University, Provo, 84602, UT, United States; Gazeas K., Section of Astrophysics, Astronomy and Mechanics, Department of Physics, National and Kapodistrian University of Athens, Zografos, Athens, GR-15784, Greece; Carosati D., Ept Observatories, Tijarafe, La Palma, E-38780, Spain, Inaf, Tng Fundaci Galileo Galilei, La Palma, E-38712, Spain; Mirzaqulov D.O., Ulugh Beg Astronomical Institute, Astronomy Street 33, Tashkent, 100052, Uzbekistan; Acosta Pulido J.A., Instituto de Astrofica de Canarias (IAC), Tenerife, La Laguna, E-38200, Spain, Departamento de Astrofica, Universidad de la Laguna (ULL), Tenerife, La Laguna, E-38206, Spain; Agudo I., Instituto de Astrofica de Andaluc (CSIC), Apartado 3004, Granada, E-18080, Spain; Bachev R., Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, 72 Tsarigradsko shosse Blvd., Sofia, 1784, Bulgaria; Benez E., Instituto de Astronom, Universidad Nacional Automa de Mico, AP 70-264, CDMX, 04510, Mexico; Borman G.A., Crimean Astrophysical Observatory Ras, P/O, 298409, Russian Federation; Calcidese P., Osservatorio Astronomico della Regione Autonoma Valle d'Aosta, Nus, I-11020, Italy; Chen W.P., Institute of Astronomy, National Central University, Taoyuan, 32001, Taiwan; Damljanovic G., Astronomical Observatory, Volgina 7, Belgrade, 11060, Serbia; Ehgamberdiev S.A., Ulugh Beg Astronomical Institute, Astronomy Street 33, Tashkent, 100052, Uzbekistan, National University of Uzbekistan, Tashkent, 100174, Uzbekistan; Elsser D., Hans-Haffner-Sternwarte (Hettstadt), Naturwissenschaftliches Labor f Scher, Friedrich-Koenig-Gymnasium, Wzburg, D-97082, Germany, Technische Universit Dortmund, Dortmund, D-44221, Germany; Feige M., Hans-Haffner-Sternwarte (Hettstadt), Naturwissenschaftliches Labor f Scher, Friedrich-Koenig-Gymnasium, Wzburg, D-97082, Germany; Frasca A., Inaf, Osservatorio Astrofisico di Catania, Via S. Sofia 78, Catania, I-95123, Italy; Gaur H., Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital, 263001, India; Grishina T.S., Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russian Federation; Gupta A.C., Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital, 263001, India; Hiriart D., Instituto de Astronom, Universidad Nacional Automa de Mico, AP 106, Baja California, Ensenada, 22800, Mexico; Holland M., Department of Physics and Astronomy, N283 Esc, Brigham Young University, Provo, 84602, UT, United States; Horst B., Hans-Haffner-Sternwarte (Hettstadt), Naturwissenschaftliches Labor f Scher, Friedrich-Koenig-Gymnasium, Wzburg, D-97082, Germany; Ibryamov S., Department of Physics and Astronomy, Faculty of Natural Sciences, University of Shumen, 115, Universitetska Str., Shumen, 9712, Bulgaria; Ivanidze R.Z., Abastumani Observatory, Mt. Kanobili, Abastumani, 0301, Georgia; Jensen J., Department of Physics and Astronomy, N283 Esc, Brigham Young University, Provo, 84602, UT, United States; Jithesh V., Department of Physics and Electronics, Christ (Deemed to Be University), Hosur Main Road, Bengaluru, 560029, India; Jovanovic M.D., Astronomical Observatory, Volgina 7, Belgrade, 11060, Serbia; Kiehlmann S., Institute of Astrophysics, Foundation for Research and Technology - Hellas, Vasilika Vouton, Heraklion, GR-70013, Greece, Department of Physics, University of Crete, Voutes University Campus, Heraklion, GR-70013, Greece; Kimeridze G.N., Abastumani Observatory, Mt. Kanobili, Abastumani, 0301, Georgia; Kishore S., Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital, 263001, India; Kopatskaya E.N., Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russian Federation; Kurtanidze O.M., Abastumani Observatory, Mt. Kanobili, Abastumani, 0301, Georgia, Engelhardt Astronomical Observatory, Kazan Federal University, Tatarstan, Russian Federation; Larionova E.G., Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russian Federation; Lin H.C., Institute of Astronomy, National Central University, Taoyuan, 32001, Taiwan; Mannheim K., Hans-Haffner-Sternwarte (Hettstadt), Naturwissenschaftliches Labor f Scher, Friedrich-Koenig-Gymnasium, Wzburg, D-97082, Germany, Universit Wzburg, Wzburg, D-97074, Germany; Marinelli C., Dip. di Scienze Fisiche, della Terra e Dell'Ambiente, Universitdi Siena, via Roma 56, Siena, I-53100, Italy; Moreira Reyes J., Department of Physics, Astronomy and Geophysics, Connecticut College, New London, 06320, CT, United States; Morozova D.A., Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russian Federation; Nikolashvili M.G., Abastumani Observatory, Mt. Kanobili, Abastumani, 0301, Georgia; Reinhart D., Hans-Haffner-Sternwarte (Hettstadt), Naturwissenschaftliches Labor f Scher, Friedrich-Koenig-Gymnasium, Wzburg, D-97082, Germany, Universit Wzburg, Wzburg, D-97074, Germany; Romanov F.D., Aavso Observer, Russian Federation, Remote Observer of Burke-Gaffney Observatory, Canada; Semkov E., Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, 72 Tsarigradsko shosse Blvd., Sofia, 1784, Bulgaria; Seufert J., Hans-Haffner-Sternwarte (Hettstadt), Naturwissenschaftliches Labor f Scher, Friedrich-Koenig-Gymnasium, Wzburg, D-97082, Germany; Shishkina E.V., Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russian Federation; Sigua L.A., Abastumani Observatory, Mt. Kanobili, Abastumani, 0301, Georgia; Skalidis R., Owens Valley Radio Observatory, California Institute of Technology, MC 249-17, Pasadena, 91125, CA, United States; Spiridonova O.I., Special Astrophysical Observatory of Russian Academy of Sciences, Nyzhnij Arkhyz,Circassia,Karachai, 369167, Russian Federation; Stojanovic M., Astronomical Observatory, Volgina 7, Belgrade, 11060, Serbia; Strigachev A., Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, 72 Tsarigradsko shosse Blvd., Sofia, 1784, Bulgaria; Troitskaya Y.V., Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russian Federation; Troitskiy I.S., Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russian Federation; Tsai A., Institute of Astronomy, National Central University, Taoyuan, 32001, Taiwan; Vasilyev A.A., Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russian Federation; Vince O., Astronomical Observatory, Volgina 7, Belgrade, 11060, Serbia; Vrontaki K., Section of Astrophysics, Astronomy and Mechanics, Department of Physics, National and Kapodistrian University of Athens, Zografos, Athens, GR-15784, Greece; Wani K., Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital, 263001, India; Watts D., Department of Physics and Astronomy, N283 Esc, Brigham Young University, Provo, 84602, UT, United States; Zhovtan A.V., Crimean Astrophysical Observatory Ras, P/O, 298409, Russian Federation