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Extreme photometric and polarimetric variability of blazar S4 0954+65 at its maximum optical and $γ$-ray brightness levels

C. M. RaiteriNational Institute for AstrophysicsM. VillataINAF , Osservatorio Astrofisico di Torino , via Osservatorio 20 , I-10025 Pino Torinese , ItalyM. I. CarnereroINAF , Osservatorio Astrofisico di Torino , via Osservatorio 20 , I-10025 Pino Torinese , ItalyС. С. СавченкоSofia O. KurtanidzeAbastumani Observatory , Mt. Kanobili , 0301 Abastumani , GeorgiaV. V. VlasyukSpecial Astrophysical Observatory of Russian Academy of Sci- ences , Nyzhnĳ Arkhyz , Karachai-Circassia , Russia, 369167Alessandro MarchiniUniversity of Siena , Astronomical Observatory , Siena , ItalyKatsura MatsumotoAstronomical Institute , Osaka Kyoiku University , Osaka 582-8582 , JapanC. LoreyM. D. JonerK. GazeasSection of Astrophysics, Astronomy and Mechanics , Department of Physics , National and Kapodistrian University of Athens , GR-15784 Zografos , Athens , GreeceD. CarosatiD. O. MirzaqulovUlugh Beg Astronomical Institute , Astronomy Street 33 , Tashkent 100052 , UzbekistanJ. A. Acosta‐PulidoInstituto de Astrofísica de Canarias (IAC) , E-38200 La Laguna , Tenerife , SpainI. AgudoINAF , Osservatorio Astrofisico di Torino , via Osservatorio 20 , I-10025 Pino Torinese , ItalyR. BachevInstitute of Astronomy and National Astronomical Observatory ,E. BenítezГ. А. БорманCrimean Astrophysical Observatory RAS , P/O Nauchny , 298409 , RussiaP. CalcideseOsservatorio Astronomico della Regione Autonoma Valle d'Aosta , I-11020 Nus , ItalyW. P. ChenInstitute of Astronomy , National Central University , Taoyuan 32001 , TaiwanG. DamljanovićAstronomical Observatory , Volgina 7 , 11060 Belgrade , SerbiaSh. A. EhgamberdievUlugh Beg Astronomical Institute , Astronomy Street 33 , Tashkent 100052 , UzbekistanDominik ElsässerM. FeigeA. FrascaINAF , Osservatorio Astrofisico di Catania , Via S. Sofia 78 , I-95123 Catania , ItalyHaritma GaurAryabhatta Research Institute of Observational Sciences (ARIES) , Manora Peak , Nainital 263001 , IndiaT. S. GrishinaSaint Petersburg State University , 7/9A. C. GuptaAryabhatta Research Institute of Observational Sciences (ARIES) , Manora Peak , Nainital 263001 , IndiaD. HiriartUniversidad Nacional Autónoma de México , Instituto de As- tronomía , AP 106 , Ensenada 22800 , Baja California , MexicoHolland, M.Department of Physics and Astronomy , N283 ESC , Brigham Young University , Provo , UT 84602 , USAHorst, B.S. IbryamovDepartment of Physics and Astronomy , Faculty of Natural Sciences , University of Shumen , 115 , Universitetska Str. , 9712 Shumen , BulgariaIvanidze RAbastumani Observatory , Mt. Kanobili , 0301 Abastumani , GeorgiaJ. JensenDepartment of Physics and Astronomy , N283 ESC , Brigham Young University , Provo , UT 84602 , USAJithesh, V.Department of Physics and Electronics , CHRIST (Deemed to be University) , Hosur Main Road , Bengaluru - 560029 , IndiaM. D. JovanovicS. KiehlmannDepartment of Physics , University of Crete , Voutes University Campus , GR-70013 Heraklion , GreeceG. N. KimeridzeAbastumani Observatory , Mt. Kanobili , 0301 Abastumani , GeorgiaShubham KishoreAryabhatta Research Institute of Observational Sciences (ARIES) , Manora Peak , Nainital 263001 , IndiaE. N. KopatskayaSaint Petersburg State University , 7/9O. M. KurtanidzeEngelhardt Astronomical Observatory , Kazan Federal University , Tatarstan , RussiaЕ. Г. ЛарионоваSaint Petersburg State University , 7/9Hung-Chin LinInstitute of Astronomy , National Central University , Taoyuan 32001 , TaiwanK. MannheimHans-Haffner-Sternwarte (Hettstadt) , Naturwissenschaftliches Labor für Schüler , Friedrich-Koenig-Gymnasium , 97082 Würzburg , GermanyC. MarinelliDip. di Scienze Fisiche , della Terra e dell'Ambiente , Università di Siena , via Roma 56 , 53100 , Siena , ItalyJ. Moreira ReyesDepartment of Physics, Astronomy and Geophysics, Connecticut College, New London, CT 06320, USA 36 AAVSO observer, Russia 37 Remote observer of Burke-Gaffney Observatory, Canada 38 Owens Valley Radio Observatory, California Institute of Technol- ogy, MC 249-17, Pasadena, CA 91125, USAD. A. MorozovaSaint Petersburg State University , 7/9M. G. NikolashviliAbastumani Observatory , Mt. Kanobili , 0301 Abastumani , GeorgiaD. ReinhartHans-Haffner-Sternwarte (Hettstadt) , Naturwissenschaftliches Labor für Schüler , Friedrich-Koenig-Gymnasium , 97082 Würzburg , GermanyF. D. RomanovE. SemkovInstitute of Astronomy and National Astronomical Observatory ,Jochen SeufertShishkina, E. V.Saint Petersburg State University , 7/9L. A. SiguaAbastumani Observatory , Mt. Kanobili , 0301 Abastumani , GeorgiaRaphael SkalidisO. I. SpiridonovaSpecial Astrophysical Observatory of Russian Academy of Sci- ences , Nyzhnĳ Arkhyz , Karachai-Circassia , Russia, 369167M. StojanovićAstronomical Observatory , Volgina 7 , 11060 Belgrade , SerbiaA. StrigachevInstitute of Astronomy and National Astronomical Observatory ,Yu. V. TroitskayaSaint Petersburg State University , 7/9I. S. TroitskiySaint Petersburg State University , 7/9An-Li TsaiInstitute of Astronomy , National Central University , Taoyuan 32001 , TaiwanA. A. VasilyevSaint Petersburg State University , 7/9O. VinceAstronomical Observatory , Volgina 7 , 11060 Belgrade , SerbiaK. VrontakiSection of Astrophysics, Astronomy and Mechanics , Department of Physics , National and Kapodistrian University of Athens , GR-15784 Zografos , Athens , GreeceWani, K.Aryabhatta Research Institute of Observational Sciences (ARIES) , Manora Peak , Nainital 263001 , IndiaWatts, D.Department of Physics and Astronomy , N283 ESC , Brigham Young University , Provo , UT 84602 , USAAlexey V. ZhovtanCrimean Astrophysical Observatory RAS , P/O Nauchny , 298409 , Russia

2023en

ABI

Annotatsiya

In 2022 the BL Lac object S4 0954+65 underwent a major variability phase, reaching its historical maximum brightness in the optical and $γ$-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 $10^{-4}$ 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 $γ$-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 $γ$-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.

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Identifikatorlar

DOI: 10.48550/arxiv.2310.11108

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