Optical and Radio Variability of the Blazar S4 0954+658

Abstract

We present an optical-to-radio study of the BL Lac object S4 0954+658 observations during 1998-2023. The measurements were obtained with the SAO RAS Zeiss-1000 1-m and AS-500/2 0.5-m telescopes in 2003-2023, with the RATAN-600 radio 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 Badary telescopes at 5.05 and 8.63 GHz in 2020--2023, and with the RT-22 single-dish telescope of CrAO RAS at 36.8 GHz in 2009-2023. In this period the blazar had been showing extremely high broadband activity with the variability amplitude of flux densities up to 70-100% both in the optical and radio domains. In the period of 2014-2023 the blazar had been showing the historically highest activity in the radio wavelengths, and we detected multiple radio flares of varying amplitude and duration. The large flares last on average from 0.3 to 1 year at 22-36.8 GHz and slightly longer at 5-11.2 GHz. The optical flares are shorter and last 7-50 days. In the most active epoch of 2018-2023 the characteristic time scale $\tau$ of variation at 5-22 GHz is about 100 days and about 1000 days for the state with lower activity in 2009-2014. We found a general correlation between the optical, radio, and $\gamma$-ray flux variations, which suggests that we observe the same photon population from different emission regions. We estimated linear size of this region as 0.5-2 pc for different epochs. A broadband two components radio spectrum of S4 0954+658 jet was modelled by using both electrons and protons as emitting particles. It is shown that the synchrotron radio waves in this AGN may be generated by relativistic protons.

arXiv commentPublished in Astrophysical Bulletin Vol.78, N4 (2023)

References in corpus (49)

• Unified Schemes for Radio-Loud Active Galactic Nuclei
• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• A Unifying View of the Spectral Energy Distributions of Blazars
• On characterising the variability properties of X-ray light curves from active galaxies
• The Spectral Energy Distribution of Fermi bright blazars
• The GMRT 150 MHz All-sky Radio Survey: First Alternative Data Release TGSS ADR1
• GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey I: A low-frequency extragalactic catalogue
• CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources
• Doppler factors, Lorentz factors and viewing angles for quasars, BL Lacertae objects and radio galaxies
• An Accurate Flux Density Scale from 1 to 50 GHz
• An Accurate Flux Density Scale from 50 MHz to 50 GHz
• Kinematics of Parsec-Scale Jets of Gamma-Ray Blazars at 43~GHz within the VLBA-BU-BLAZAR Program
• The Australia Telescope 20 GHz Survey: The Source Catalogue
• The transition between BL Lac objects and Flat Spectrum Radio Quasars
• Modeling the Emission Processes in Blazars
• Generating artificial light curves: Revisited and updated
• The WEBT BL Lac Campaign 2000
• Multi-colour optical monitoring of eight red blazars
• Observational evidence for the origin of high-energy neutrinos in parsec-scale nuclei of radio-bright active galaxies
• Directional association of TeV to PeV astrophysical neutrinos with radio blazars
• The Australia Telescope 20 GHz (AT20G) Survey: The Bright Source Sample
• Near Infrared Intraday Variability of Mrk 421
• Optical Flux and Spectral Variability of Blazars
• Spectral Slope Variability of BL Lac Objects in the Optical Band
• Multiwavelength Cross-Correlations and Flaring Activity in Bright Blazars
• A Dual Frequency, Multi-Year Monitoring Program of Compact Radio Sources
• An innovative blazar classification based on radio jet kinematics
• Multiwavelength behaviour of the blazar 3C279: decade-long study from $\gamma$-ray to radio
• Optical variability of PKS 0736+017
• The Planck-ATCA Co-eval Observations (PACO) project: the bright sample
• A Consolidated Framework of the Color Variability in Blazars: Long-Term Optical/Near-Infrared Observations of 3C 279
• A peculiar multi-wavelength flare in the Blazar 3C 454.3
• Interplanetary Scintillation with the Murchison Widefield Array I: A sub-arcsecond Survey over 900 square degrees at 79 and 158 MHz
• F-GAMMA: Multi-frequency radio monitoring of Fermi blazars. The 2.64 to 43 GHz Effelsberg light curves from 2007-2015
• Detection statistics of the RadioAstron AGN survey
• The CATS Service: an Astrophysical Research Tool
• RATAN-600 multi-frequency data for the BL Lac objects
• Simultaneous Multiwavelength and Optical Microvariability Observations of CTA 102 (PKS J2232+1143)
• Optical spectral characterization of the gamma-ray blazars S4 0954+65, TXS 1515-273 and RX J0812.0+0237
• On the classification of flaring states of blazar
• Bendings of radio jets in BL Lacertae objects I: EVN and MERLIN observations
• Detection of Quasi-Periodic Oscillations in the Blazar S4 0954+658 with TESS
• Observations of flat-spectrum radio sources at 850 microns from the James Clerk Maxwell Telescope II. April 2000 to June 2005
• Exploring Short-Term Optical Variability of Blazars Using $\text{TESS}$
• Effelsberg Monitoring of a Sample of RadioAstron Blazars: Analysis of Intra-Day Variability
• Simultaneous spectra and radio properties of BL Lac's
• Catching profound optical flares in blazars
• Radio Variability and Broad-Band Spectra of Infrared Galaxies with and without OH Megamaser Emission
• The spectral variability of FSRQs

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