Rapid quasi-periodic oscillations in the relativistic jet of BL Lacertae

Publication date: 
Main author: 
Jorstad, S. G.
IAA authors: 
Gómez, J. L.;Bonnoli, G.
Jorstad, S. G.;Marscher, A. P.;Raiteri, C. M.;Villata, M.;Weaver, Z. R.;Zhang, H.;Dong, L.;Gómez, J. L.;Perel, M. V.;Savchenko, S. S.;Larionov, V. M.;Carosati, D.;Chen, W. P.;Kurtanidze, O. M.;Marchini, A.;Matsumoto, K.;Mortari, F.;Aceti, P.;Acosta-Pulido, J. A.;Andreeva, T.;Apolonio, G.;Arena, C.;Arkharov, A.;Bachev, R.;Banfi, M.;Bonnoli, G.;Borman, G. A.;Bozhilov, V.;Carnerero, M. I.;Damljanovic, G.;Ehgamberdiev, S. A.;Elsässer, D.;Frasca, A.;Gabellini, D.;Grishina, T. S.;Gupta, A. C.;Hagen-Thorn, V. A.;Hallum, M. K.;Hart, M.;Hasuda, K.;Hemrich, F.;Hsiao, H. Y.;Ibryamov, S.;Irsmambetova, T. R.;Ivanov, D. V.;Joner, M. D.;Kimeridze, G. N.;Klimanov, S. A.;Knött, J.;Kopatskaya, E. N.;Kurtanidze, S. O.;Kurtenkov, A.;Kuutma, T.;Larionova, E. G.;Leonini, S.;Lin, H. C.;Lorey, C.;Mannheim, K.;Marino, G.;Minev, M.;Mirzaqulov, D. O.;Morozova, D. A.;Nikiforova, A. A.;Nikolashvili, M. G.;Ovcharov, E.;Papini, R.;Pursimo, T.;Rahimov, I.;Reinhart, D.;Sakamoto, T.;Salvaggio, F.;Semkov, E.;Shakhovskoy, D. N.;Sigua, L. A.;Steineke, R.;Stojanovic, M.;Strigachev, A.;Troitskaya, Y. V.;Troitskiy, I. S.;Tsai, A.;Valcheva, A.;Vasilyev, A. A.;Vince, O.;Waller, L.;Zaharieva, E.;Chatterjee, R.
Publication type: 
Blazars are active galactic nuclei (AGN) with relativistic jets whose non-thermal radiation is extremely variable on various timescales<SUP>1-3</SUP>. This variability seems mostly random, although some quasi-periodic oscillations (QPOs), implying systematic processes, have been reported in blazars and other AGN. QPOs with timescales of days or hours are especially rare<SUP>4</SUP> in AGN and their nature is highly debated, explained by emitting plasma moving helically inside the jet<SUP>5</SUP>, plasma instabilities<SUP>6,7</SUP> or orbital motion in an accretion disc<SUP>7,8</SUP>. Here we report results of intense optical and γ-ray flux monitoring of BL Lacertae (BL Lac) during a dramatic outburst in 2020 (ref. <SUP>9</SUP>). BL Lac, the prototype of a subclass of blazars<SUP>10</SUP>, is powered by a 1.7 × 10<SUP>8</SUP> M<SUB>Sun</SUB> (ref. <SUP>11</SUP>) black hole in an elliptical galaxy (distance = 313 megaparsecs (ref. <SUP>12</SUP>)). Our observations show QPOs of optical flux and linear polarization, and γ-ray flux, with cycles as short as approximately 13 h during the highest state of the outburst. The QPO properties match the expectations of current-driven kink instabilities<SUP>6</SUP> near a recollimation shock about 5 parsecs (pc) from the black hole in the wake of an apparent superluminal feature moving down the jet. Such a kink is apparent in a microwave Very Long Baseline Array (VLBA) image.
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