The extreme blazar AO 0235+164 as seen by extensive ground and space radio observations

Abstract

Clues to the physical conditions in radio cores of blazars come from measurements of brightness temperatures as well as effects produced by intrinsic opacity. We study the properties of the ultra compact blazar AO 0235+164 with RadioAstron ground-space radio interferometer, multi-frequency VLBA, EVN and single-dish radio observations. We employ visibility modeling and image stacking for deriving structure and kinematics of the source, and use Gaussian process regression to find the relative multi-band time delays of the flares. The multi-frequency core size and time lags support prevailing synchrotron self absorption. The intrinsic brightness temperature of the core derived from ground-based VLBI is close to the equipartition regime value. In the same time, there is evidence for ultra-compact features of the size of less than 10 $\mu$as in the source, which might be responsible for the extreme apparent brightness temperatures of up to $10^{14}$ K as measured by RadioAstron. In 2007--2016 the VLBI components in the source at 43 GHz are found predominantly in two directions, suggesting a bend of the outflow from southern to northern direction. The apparent opening angle of the jet seen in the stacked image at 43 GHz is two times wider than that at 15 GHz, indicating a collimation of the flow within the central 1.5 mas. We estimate the Lorentz factor $\Gamma =14$, the Doppler factor $\delta =21$, and the viewing angle $\theta =1.7^{\circ }$ of the apparent jet base, derive the gradients of magnetic field strength and electron density in the outflow, and the distance between jet apex and the core at each frequency.

arXiv commentAccepted for publication in MNRAS. 18 pages, 18 figures

References in corpus (42)

• emcee: The MCMC Hammer
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• On Uncertainties in Cross-Correlation Lags and the Reality of Wavelength-Dependent Continuum Lags in Active Galactic Nuclei
• Blazars in the Fermi Era: The OVRO 40-m Telescope Monitoring Program
• Doppler factors, Lorentz factors and viewing angles for quasars, BL Lacertae objects and radio galaxies
• Multi-Epoch VLBA Observations of EGRET-Detected Quasars and BL Lac Objects: Superluminal Motion of Gamma-Ray Bright Blazars
• Sub-milliarcsecond Imaging of Quasars and Active Galactic Nuclei. IV. Fine Scale Structure
• Kinematics of Parsec-Scale Jets of Gamma-Ray Blazars at 43~GHz within the VLBA-BU-BLAZAR Program
• Particle acceleration at ultrarelativistic shocks: an eigenfunction method
• RadioAstron -- a Telescope with a Size of 300 000 km: Main Parameters and First Observational Results
• Kinematics of the jet in M87 on scales of 100 -- 1000 Schwarzschild radii
• Master Robotic Net
• MOJAVE - XIV. Shapes and opening angles of AGN jets
• Opacity in compact extragalactic radio sources and its effect on astrophysical and astrometric studies
• A VLBA survey of the core shift effect in AGN jets I. Evidence for dominating synchrotron opacity
• A method for the estimation of the significance of cross-correlations in unevenly sampled red-noise time series
• The SFXC software correlator for Very Long Baseline Interferometry: Algorithms and Implementation
• On the Location of the Gamma-ray Emission in the 2008 Outburst in the BL Lacertae Object AO 0235+164 through Observations across the Electromagnetic Spectrum
• Kinetic Luminosity and Composition of Active Galactic Nuclei Jets
• The VLBA Galactic Plane Survey -- VGaPS
• VLBI-Gaia offsets favor parsec-scale jet direction in Active Galactic Nuclei
• RadioAstron Observations of the Quasar 3C273: a Challenge to the Brightness Temperature Limit
• Theory and Simulations of Refractive Substructure in Resolved Scatter-Broadened Images
• On significance of VLBI/Gaia position offsets
• Milky Way scattering properties and intrinsic sizes of active galactic nuclei cores probed by very long baseline interferometry surveys of compact extragalactic radio sources
• The core shift effect in the blazar 3C 454.3
• Multi-wavelength observations of blazar AO 0235+164 in the 2008-2009 flaring state
• A connection between $\gamma$-ray and parsec-scale radio flares in the blazar 3C 273
• A new method for estimating frequency-dependent core shifts in active galactic nucleus jets
• Doppler Boosting, Superluminal Motion, and the Kinematics of AGN Jets
• Observational consequences of optical band milliarcsecond-scale structure in active galactic nuclei discovered by Gaia
• Interstellar Scintillation Observations of 146 Extragalactic Radio Sources
• Extreme Brightness Temperatures and Refractive Substructure in 3C273 with RadioAstron
• Software correlator for Radioastron mission
• Brightness temperature constraints from interferometric visibilities
• Dual-Frequency VSOP Observations of AO 0235+164
• A relativistic helical jet in the gamma-ray AGN 1156+295
• Radio structure of the blazar 1156+295 with sub-pc resolution
• What can the 2008/10 broadband flare of PKS 1502+106 tell us? Nuclear opacity, magnetic fields, and the location of gamma rays
• Constraints on the gamma-ray emitting region in blazars from multi-frequency VLBI measurements
• Constraining the magnetic field in the parsec-scale jets of the brightest Fermi blazars with multifrequency VLBI observations
• The Apparent "Angular Size - Frequency" Dependence in ~3000 Parsec-scale Extragalactic Jets

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• Quasi-Periodic Oscillations in the long term radio light curves of the blazar AO 0235+164
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• Multi-frequency study of the gamma-ray flaring BL Lac object PKS 2233-148 in 2009-2012
• A multiband study and exploration of the radio wave - $\gamma$-ray connection in 3C 84
• A comprehensive study on the variation phenomena of AO 0235+164
• Frequency-Dependent Core Shifts in Ultracompact Quasars
• Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron IV. The quasar 3C 345 at 18 cm: Magnetic field structure and brightness temperature
• A bias in VLBI measurements of the core shift effect in AGN jets
• Continuum source catalog for the first APERTIF data release
• Locations of optical and $\gamma$-ray emitting regions in the jet of PMN J2345-1555
• Opacity, variability and kinematics of AGN jets
• Multiwavelength variability of the blazar AO 0235+164
• The Repeating Flaring Activity of Blazar AO 0235+164
• 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
• Study of variability in long-term multiwavelength optical lightcurves of blazar AO 0235+164
• Inverse Compton Scattering of the Central Source Photons as an X-ray Emission Mechanism on Kiloparsec Scales in PKS 1127-145
• Inverse Compton Scattering of Radiation from a Central Source as a Possible Mechanism for the Formation of X-Ray Radiation from Kiloparsec Jets of Core-Dominated Quasars
• Parsec-scale jet precession and a putative supermassive binary black hole system in the blazar AO 0235+164