The complex variability of blazars: time-scales and periodicity analysis in S4 0954+65
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Accepted manuscript
Date
2021-05-21
Authors
Raiteri, C.M.
Villata, M.
Larionov, V.M.
Jorstad, S.G.
Marscher, Alan P.
Weaver, Z.R.
Acosta-Pulido, J.A.
Agudo, Ivan
Andreeva, T.S.
Arkharov, A.A.
Version
Accepted manuscript
OA Version
Citation
C.M. Raiteri, M. Villata, V.M. Larionov, S.G. Jorstad, A.P. Marscher, Z.R. Weaver, J.A. Acosta-Pulido, I. Agudo, T. Andreeva, A. Arkharov, R. Bachev, E. Benítez, M. Berton, I. Björklund, G.A. Borman, V. Bozhilov, M.I. Carnerero, D. Carosati, C. Casadio, W.P. Chen, G. Damljanovic, F. D’Ammando, J. Escudero, A. Fuentes, M. Giroletti, T.S. Grishina, A.C. Gupta, V.A. Hagen-Thorn, M. Hart, D. Hiriart, W.-.J. Hou, D. Ivanov, J.-.Y. Kim, G.N. Kimeridze, C. Konstantopoulou, E.N. Kopatskaya, O.M. Kurtanidze, S.O. Kurtanidze, A. Lähteenmäki, E.G. Larionova, L.V. Larionova, N. Marchili, G. Markovic, M. Minev, D.A. Morozova, I. Myserlis, M. Nakamura, A.A. Nikiforova, M.G. Nikolashvili, J. Otero-Santos, E. Ovcharov, T. Pursimo, I. Rahimov, S. Righini, T. Sakamoto, S.S. Savchenko, E.H. Semkov, D. Shakhovskoy, L.A. Sigua, M. Stojanovic, A. Strigachev, C. Thum, M. Tornikoski, E. Traianou, Y.V. Troitskaya, I.S. Troitskiy, A. Tsai, A. Valcheva, A.A. Vasilyev, O. Vince, E. Zaharieva. 2021. "The complex variability of blazars: time-scales and periodicity analysis in S4 0954+65." Monthly Notices of the Royal Astronomical Society, Volume 504, Issue 4, pp. 5629 - 5646. https://doi.org/10.1093/mnras/stab1268
Abstract
Among active galactic nuclei, blazars show extreme variability properties. We here investigate the case of the BL Lac object S4 0954+65 with data acquired in 2019–2020 by the Transiting Exoplanet Survey Satellite (TESS) and by the Whole Earth Blazar Telescope (WEBT) Collaboration. The 2-min cadence optical light curves provided by TESS during three observing sectors of nearly 1 month each allow us to study the fast variability in great detail. We identify several characteristic short-term time-scales, ranging from a few hours to a few days. However, these are not persistent, as they differ in the various TESS sectors. The long-term photometric and polarimetric optical and radio monitoring undertaken by the WEBT brings significant additional information, revealing that (i) in the optical, long-term flux changes are almost achromatic, while the short-term ones are strongly chromatic; (ii) the radio flux variations at 37 GHz follow those in the optical with a delay of about 3 weeks; (iii) the range of variation of the polarization degree and angle is much larger in the optical than in the radio band, but the mean polarization angles are similar; (iv) the optical long-term variability is characterized by a quasi-periodicity of about 1 month. We explain the source behaviour in terms of a rotating inhomogeneous helical jet, whose pitch angle can change in time.
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© 2020 The Authors.