English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We present an optical-to-radio study of the BL Lac object S4 0954+658observations during 1998-2023. The measurements were obtained with the SAO RASZeiss-1000 1-m and AS-500/2 0.5-m telescopes in 2003-2023, with the RATAN-600radio telescope at 1.25 (0.96, 1.1), 2.3, 4.7 (3.7, 3.9), 8.2 (7.7), 11.2, 22.3(21.7) GHz in 1998-2023, with the IAA RAS RT-32 Zelenchukskaya and Badarytelescopes at 5.05 and 8.63 GHz in 2020--2023, and with the RT-22 single-dishtelescope of CrAO RAS at 36.8 GHz in 2009-2023. In this period the blazar hadbeen showing extremely high broadband activity with the variability amplitudeof flux densities up to 70-100% both in the optical and radio domains. In theperiod of 2014-2023 the blazar had been showing the historically highestactivity in the radio wavelengths, and we detected multiple radio flares ofvarying amplitude and duration. The large flares last on average from 0.3 to 1year at 22-36.8 GHz and slightly longer at 5-11.2 GHz. The optical flares areshorter and last 7-50 days. In the most active epoch of 2018-2023 thecharacteristic time scale $\tau$ of variation at 5-22 GHz is about 100 days andabout 1000 days for the state with lower activity in 2009-2014. We found ageneral correlation between the optical, radio, and $\gamma$-ray fluxvariations, which suggests that we observe the same photon population fromdifferent emission regions. We estimated linear size of this region as 0.5-2 pcfor different epochs. A broadband two components radio spectrum of S4 0954+658jet was modelled by using both electrons and protons as emitting particles. Itis shown that the synchrotron radio waves in this AGN may be generated byrelativistic protons.

Optical and Radio Variability of the Blazar S4 0954+658