Blazar spectral variability as explained by a twisting inhomogeneous jet

Abstract

Blazar emission is dominated by non-thermal radiation from a relativistic jet pointing toward us, therefore undergoing Doppler beaming. This is responsible for flux enhancement and contraction of the variability time scales, so that most blazars appear as luminous sources characterized by noticeable and fast flux changes at all frequencies. The mechanisms producing their unpredictable variability are debated and include injection, acceleration and cooling of particles, with possible intervention of shock waves or turbulence. Changes in the viewing angle of the emitting knots or jet regions have also been suggested to explain flaring events or specific properties such as intraday variability, quasi-periodicities, or the delay of radio flux variations relative to optical changes. However, such a geometric interpretation has not been universally accepted because alternative explanations based on changes of physical conditions can also work in many cases. Here we report the results of optical-to-radio monitoring of the blazar CTA 102 by the Whole Earth Blazar Telescope Collaboration and show that the observed long-term flux and spectral variability is best explained by an inhomogeneous, curved jet that undergoes orientation changes. We propose that magnetohydrodynamic instabilities or rotation of a twisted jet cause different jet regions to change their orientation and hence their relative Doppler factors. In particular, the recent extreme optical outburst (six magnitudes) occurred when the corresponding jet emitting region acquired a minimum viewing angle.

arXiv comment31 pages, 11 figures. This is the accepted version (before Nature editing) of the paper published by Nature, online version at http://dx.doi.org/10.1038/nature24623, Nature 2017/12/04/online

References in corpus (27)

• Unified Schemes for Radio-Loud Active Galactic Nuclei
• Empirical Color Transformations Between SDSS Photometry and Other Photometric Systems
• Structured jets in TeV BL Lac objects and radiogalaxies
• Turbulent, Extreme Multi-Zone Model for Simulating Flux and Polarization Variability in Blazars
• Canonical high power blazars
• Log-parabolic spectra and particle acceleration in the BL Lac object Mkn 421: spectral analysis of the complete BeppoSAX wide band X-ray data set
• A change in the optical polarization associated with a gamma-ray flare in the blazar 3C 279
• Swift observations of the very intense flaring activity of Mrk 421 during 2006: I. Phenomenological picture of electron acceleration and predictions for the MeV/GeV emission
• Relativistic beaming and gamma-ray brightness of blazars
• The unprecedented optical outburst of the quasar 3C 454.3. The WEBT campaign of 2004-2005
• High Resolution 3D Relativistic MHD Simulations of Jets
• On the geometrical origin of periodicity in blazar-type sources
• Low power BL Lacertae objects and the blazar sequence: Clues on the particle acceleration process
• Catching the Radio Flare in CTA 102 III. Core-Shift and Spectral Analysis
• Helical jets in blazars. Interpretation of the multifrequency long-term variability of AO 0235+16
• Modeling the production of flares in $\gamma$-ray quasars
• The correlated optical and radio variability of BL Lacertae. WEBT data analysis 1994-2005
• Emission from Hot Dust in the Infrared Spectra of Gamma-ray Bright Blazars
• Anatomy of helical relativistic jets: The case of S5 0836+710
• A multi-wavelength polarimetric study of the blazar CTA 102 during a Gamma-ray flare in 2012
• A 3.5mm Polarimetric Survey of Radio-loud Active Galactic Nuclei
• Exceptional outburst of the blazar CTA 102 in 2012: The GASP-WEBT campaign and its extension
• Polarization swings in blazars
• The nature of optical and near-infrared variability of BL Lacertae
• A spine-sheath model for strong-line blazars
• Infrared properties of blazars: putting the GASP-WEBT sources into context
• High-redshift blazars through nustar eyes

Cited by in corpus (119)

• Kinematics of Parsec-Scale Jets of Gamma-Ray Bright Blazars at 43 GHz during Ten Years of the VLBA-BU-BLAZAR Program
• Gaia Data Release 3: The extragalactic content
• The Birth of a Relativistic Jet Following the Disruption of a Star by a Cosmological Black Hole
• Gamma-ray quasi-periodicities of blazars. A cautious approach
• Quasi-periodicities of BL Lac Objects
• Quasi-periodic behaviour in the optical and γ-ray light curves of blazars 3C 66A and B2 1633+38
• The dual nature of blazar fast variability. Space and ground observations of S5 0716+714
• Multiwavelength behaviour of the blazar 3C279: decade-long study from $\gamma$-ray to radio
• Filamentary structures as the origin of blazar jet radio variability
• Investigation of the correlation patterns and the Compton dominance variability of Mrk 421 in 2017
• Looking at Blazar Light Curve Periodicities with Gaussian Processes
• On the multi-wavelength Emission from CTA 102
• Two Flares with One Shock: the Interesting Case of 3C 454.3
• The complex variability of blazars: Time-scales and periodicity analysis in S4 0954+65
• Multi-waveband quasi-periodic oscillations in the light curves of blazar CTA 102 during its 2016-2017 optical outburst
• Long term variability and correlation study of the blazar 3C 454.3 in radio, NIR and optical wavebands
• The magnetic field structure in CTA 102 from high resolution mm-VLBI observations during the flaring state in 2016-2017
• Multi-messenger characterization of Mrk 501 during historically low X-ray and $\gamma$-ray activity
• Multiwavelength periodicity search in a sample of $\gamma$-ray bright blazars
• ALMA resolves the remarkable molecular jet and rotating wind in the extremely radio-quiet galaxy NGC 1377
• Connecting steady emission and Very High Energy flaring states in blazars: the case of Mrk 421
• Flare-like Variability of the Mg~II $\lambda$2798 Å Emission Line and UV Fe~II band in the Blazar CTA~102
• Investigating the multiwavelength behaviour of the flat spectrum radio quasar CTA 102 during 2013-2017
• Multicolor Optical Monitoring of the Blazar S5 0716+714 from 2017 to 2019
• Revealing the Nature of Blazar Radio Cores through Multi-Frequency Polarization Observations with the Korean VLBI Network
• An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state
• Exploring the origin of multiwavelength activities of high-redshift FSRQ PKS 1502+106 during 2014-2018
• The TeV-emitting radio galaxy 3C 264. VLBI kinematics and SED modeling
• Gaia Data Release 3: The first Gaia catalogue of variable AGN
• Variability studies and modeling of the blazar PKS 2155-304 in the light of a decade of multi-wavelength observations
• The optical behaviour of BL Lacertae at its maximum brightness levels: a blend of geometry and energetics
• Curvature induced polarization and spectral index behavior for PKS 1502+106
• The extended flare in CTA 102 in 2016 and 2017 within a hadronic model through cloud ablation by the relativistic jet
• Detection of a quasi-periodic oscillation in the optical light curve of the remarkable blazar AO 0235+164
• Modeling the Broadband Emission of 3C 454.3
• CTA 102 in exceptionally high state during 2016-17
• Characterization of Variability in Blazar Light curves
• A statistical study of the optical spectral variability in gamma-ray blazars
• A comprehensive study on the variation phenomena of AO 0235+164
• Imaging and variability studies of CTA~102 during the 2016 January $\gamma$-ray flare
• Testing relativistic boost as the cause of gamma-ray quasi-periodic oscillation in a blazar
• The gamma-ray and Optical Variability Analysis of the BL Lac Object 3FGL J0449.4-4350
• A geometrical interpretation for the properties of multiband optical variability of the blazar S5 0716+714
• Modeling the time variable spectral energy distribution of the blazar CTA 102 from 2008 to 2022
• Numerical Analysis of Long-term Variability of AGN Jets through RMHD Simulations
• Magnetic Field Strengths of the Synchrotron Self-Absorption Region in the Jet of CTA 102 During Radio Flares
• A wiggling filamentary jet at the origin of the blazar multi-wavelength behaviour
• Blazar variability with the Vera C. Rubin Legacy Survey of Space and Time (LSST)
• The variability of blazars throughout the electromagnetic spectrum
• Polarimetric Properties of Blazars Caught by the WEBT
• Flare echos from relaxation shocks in perturbed relativistic jets
• Exploring the Nature of the 2016 γ-ray Emission in the Blazar 1749+096
• Exploring Short-Term Optical Variability of Blazars Using $\text{TESS}$
• Association of the IceCube neutrinos with blazars in the CGRaBS sample
• Optical variability of the blazar 3C 371: from minute to year timescales
• Optical and Gamma-Ray Variability Behaviors of 3C 454.3 from 2006 to 2011
• Optical Spectral Variations of a Large Sample of Fermi Blazars
• Characterizing the optical nature of the blazar S5 1803+784 during its 2020 flare
• Rapid X-ray Variability in Mkn 421 during a Multiwavelength Campaign
• The optical spectral features of 27 Fermi blazars
• Locations of optical and $\gamma$-ray emitting regions in the jet of PMN J2345-1555
• Multi-year characterisation of the broad-band emission from the intermittent extreme BL Lac 1ES~2344+514
• The beamed jet and quasar core of the distant blazar 4C 71.07
• Interpreting the variation phenomena of B2 1633+382 via the two-component model
• Jet Collimation and Acceleration in the Flat Spectrum Radio Quasar 1928+738
• Temporal variability and estimation of jet parameters for Ton 599
• Deterministic Aspect of the $\gamma$-ray Variability in Blazars
• Gamma-ray-emitting narrow-line Seyfert 1 galaxies: the Swift view
• Catching profound optical flares in blazars
• The variability patterns of the TeV blazar PG 1553+113 from a decade of MAGIC and multi-band observations
• Optical variability of a newly discovered blazar sample from the BZCAT Catalog
• Revisiting radio variability of the blazar 3C 454.3
• Observational Evidence of a Centi-parsec Supermassive Black Hole Binary Existing in the Nearby Galaxy M81
• Signature of stochastic acceleration and cooling processes in an outburst phase of the TeV blazar ON 231
• An Explanation for 13 consecutive days activities of Mrk 421
• Correlations between $\gamma$-ray luminosity and magnetization of the jet as well as relativistic electron injection power:cases for Mrk 421, 3C 454.3 and 3C 279
• Short time-scale variability of $\gamma$-ray-emitting narrow-line Seyfert 1 galaxies in optical and UV bands
• Configuration of the global magnetic field in AGN parsec-scale jets
• Study of variability in long-term multiwavelength optical lightcurves of blazar AO 0235+164
• Polarization of Astrophysical Events with Precessing Jets
• Investigating Optical Variability of the Blazar S5 0716+714 On Diverse Time-scales
• Unveiling the monster heart: unbeamed properties of blazar 4C 71.07
• Testing particle acceleration in blazar jets with continuous high-cadence optical polarization observations
• Long-term multi-wavelength variations of Fermi blazar 3C 279
• Polarization Studies in Different Blazar Types. Part I: Correlation between Optical Brightness and Polarization Degree
• Investigating the origin of optical flares from the TeV blazar S4 0954+65
• Follow-up Observations for IceCube-170922A: Detection of Rapid Near-Infrared Variability and Intensive Monitoring of TXS 0506+056
• Multiband Optical Variability of the Blazar 3C 454.3 on Diverse Timescales
• Transient QPOs of Fermi-LAT blazars under the Curved Jet Model
• Time-Dependent Modeling of the Sub-Hour Spectral Evolution During the 2013 Outburst of Mrk 421
• Separating source-intrinsic and Lorentz invariance violation induced delays in the very high energy emission of blazar flares
• A numerical study on the role of instabilities on multi-wavelength emission signatures of blazar jets
• The dynamics of the parsec-scale jet in the neutrino blazar PKS 0735+178
• Multiband optical variability on diverse timescales of the blazar Ton 599 from 2011 to 2023
• Constraining Evolution of Magnetic Field Strength in Dissipation Region of Two BL Lac Objects
• The Method of Searching for Rotations of the Polarization Position Angle of Quasars
• Very-high-energy gamma-ray detection and long-term multi-wavelength view of the flaring blazar B2 1811+31
• Multi-band optical variability of the blazar OP 313 in the outburst state during 2024-2025
• Multi-band optical variability on diverse timescales of blazar 1E 1458.8+2249
• First detection of VHE gamma-ray signal from the FSRQ TON 0599
• Effects of non-continuous inverse Compton cooling in blazars
• PKS 2155-304: Long-Term Optical Photometric Monitoring and Variability Analysis
• Twenty years of blazar monitoring with the INAF radio telescopes
• Progress in Multiwavelength and Multi-Messenger Observations of Blazars and Theoretical Challenges
• Multi-wavelength variability analysis of the blazar S5 0716+714 during a long-lasting period of low activity
• Shortterm optical variability of 4C 29.45
• Gamma-ray flares from the jet of the blazar CTA 102 in 2016-2018
• Spectral Hardening Revealed by Geometric De-boosting in the Masked Jet of PKS 2155$-$304
• A precessing jet from a supermassive black hole: multi-wavelength observations of S5 1044+71
• Relativistic Jets in Gamma-Ray-Emitting Narrow-Line Seyfert 1 Galaxies
• Unveiling the Complex Jet Dynamics in the Blazar 2021+317 through Multi-Epoch VLBI Observations
• Constraints on magnetic field and particle content in blazar jets through optical circular polarization
• Identifying changing jets through their radio variability
• Testing Weak Equivalence Principle with IceCube Event and Blazar
• Peculiar Behavior of Optical Polarization in Blazar 1ES 1959+650: Role of Jet Magnetic Field and Geometry
• Fast Optical Variability of the TeV Blazar PKS 1725+123 Observed by SVOM-VT and Insights from Multi-wavelength Follow-up Observations
• The Long-Lasting Activity in the Flat Spectrum Radio Quasar (FSRQ) CTA~102
• Multi-Band Optical Variability of Blazar 1ES 2344+514 on Diverse Time-Scales
• Automating the detection of polarization angle rotations in blazars. Re-analysis of RoboPol data reveals 27 new rotations