Cm-Wavelength Total Flux and Linear Polarization Properties of Radio-Loud BL Lacertae Objects

Abstract

Results from a long-term program to quantify the range of behavior of the cm-wavelength total flux and linear polarization variability properties of a sample of 41 radio-loud BL Lac objects using weekly to tri-monthly observations with the University of Michigan 26-m telescope operating at 14.5, 8.0, and 4.8 GHz are presented; these observations are used to identify class-dependent differences between these BL Lacs and QSOs in the Pearson-Readhead sample. The BL Lacs are found to be more highly variable in total flux density than the QSOs, exhibiting changes that are often nearly-simultaneous and of comparable amplitude at 14.5 and 4.8 GHz in contrast to the behavior in the QSOs and supporting the existence of class-dependent differences in opacity within the parsec-scale jet flows. Structure function analyses of the flux observations quantify that a characteristic timescale is identifiable in only 1/3 of the BL Lacs. The time-averaged fractional linear polarizations are only on the order of a few percent and are consistent with the presence of tangled magnetic fields within the emitting regions. In many sources a preferred long-term orientation of the EVPA is present; when compared with the VLBI structural axis, no preferred position angle difference is identified. The polarized flux typically exhibits variability with timescales of months to a few years and shows the signature of a propagating shock during several resolved outbursts. The observations indicate that the source emission is predominately due to evolving source components and support the occurrence of more frequent shock formation in BL Lac parsec-scale flows than in QSO jets. The differences in variability behavior and polarization between BL Lacs and QSOs can be explained by differences in jet stability.

1 LaTex (aastex) file, 21 postscript figure files, 2 external LaTex table files. To appear in the Astrophysical Journal

References in corpus (5)

• Sub-milliarcsecond Imaging of Quasars and AGN
• The Identification of EGRET Sources with Flat-Spectrum Radio Sources
• Extraordinary Activity in the BL Lac Object OJ~287
• Spectral distributions in compact radio sources I. Imaging with VLBI data
• A 5-GHz Southern Hemisphere VLBI Survey of Compact Radio Sources - II

Cited by in corpus (65)

• Blazars in the Fermi Era: The OVRO 40-m Telescope Monitoring Program
• Gamma-ray Light Curves and Variability of Bright Fermi-Detected Blazars
• Optical and radio behaviour of the BL Lacertae object 0716+714
• Optical and radio variability of the BL Lac object AO 0235+16: a possible 5-6 year periodicity
• On the use of structure functions to study blazar variability: caveats and problems
• MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. XI. Spectral distributions
• The Caltech-NRAO Stripe 82 Survey (CNSS) Paper I: The Pilot Radio Transient Survey In 50 deg${}^2$
• Radio Variability of Radio Quiet and Radio Loud Quasars
• PKS 1502+106: a new and distant gamma-ray blazar in outburst discovered by the Fermi Large Area Telescope
• Statistical analyses of long-term variability of AGN at high radio frequencies
• SubmilliJansky Transients in Archival Radio Observations
• Pearson-Readhead Survey Sources II: The Longterm Centimeter-band Total Flux and Linear Polarization Properties of a Complete Radio Sample
• A multifrequency analysis of radio variability of blazars
• Predictions on high frequency polarization properties of extragalactic radio sources and implications for CMB polarization measurements
• Parsec-Scale Blazar Monitoring: Flux and Polarization Variability
• Long-term radio variability of AGN: flare characteristics
• Intrinsic Differences in the Inner Jets of High- and Low-Optically Polarized Radio Quasars
• The Unanticipated Phenomenology of the Blazar PKS~2131$-$021: A Unique Super-Massive Black Hole Binary Candidate
• Multi-wavelength variability properties of Fermi blazar S5 0716+714
• The jet of Markarian 501 from millions of Schwarzschild radii down to a few hundreds
• Ten-year optical monitoring of PKS 0735+178: historical comparison, multiband behaviour and variability timescales
• A new method for estimating frequency-dependent core shifts in active galactic nucleus jets
• Harmonic QPOs and Thick Accretion Disk Oscillations in BL Lac Object AO 0235+164
• Multiwavelength Observations of Radio-quiet Quasars with Weak Emission Lines
• The kinematics in the pc-scale jets of AGN The case of S5 1803+784
• The WEBT campaign to observe AO 0235+16 in the 2003-2004 observing season
• Probing the Parsec-scale Accretion Flow of 3C 84 with Millimeter Polarimetry
• Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71: II. A search for intra-day variability at millimetre wavelengths with the IRAM 30 m telescope
• High-frequency polarization properties of southern Kuhr sources
• Precession-induced Variability in AGN Jets and OJ 287
• Long-term variability of radio-bright BL Lacertae objects
• MOJAVE XVI: Multi-Epoch Linear Polarization Properties of Parsec-Scale AGN Jet Cores
• A possible jet precession in the periodic quasar B0605-085
• Long-term variability of extragalactic radio sources in the Planck Early Release Compact Source Catalogue
• Bimodal radio variability in OVRO-40m-monitored blazars
• Very Long Baseline polarimetry and the gamma-ray connection in Markarian 421 during the broadband campaign in 2011
• Multiwavelength variability power spectrum analysis of the blazars 3C 279 and PKS 1510-089 on multiple timescales
• Untangling Optical Emissions of the Jet and Accretion Disk in the Flat-Spectrum Radio Quasar 3C 273 with Reverberation Mapping Data
• Blazar variability power spectra from radio up to TeV photon energies: Mrk 421 and PKS 2155-304
• Core shift effect in blazars
• Frequency-dependent time delays for strong outbursts in four blazars from the Metsahovi and UMRAO monitoring databases
• Optical and Radio Variability of BL Lacertae
• The Relativistic Jet Orientation and Host Galaxy of the Peculiar Blazar PKS 1413+135
• Unusual optical quiescence of the classical BL Lac object PKS 0735+178 on intranight time scale
• The milliarcsecond-scale jet of PKS 0735+178 during quiescence
• Relativistic Beaming and Flux Variability in Active Galactic Nuclei
• Radio-optical flux behavior and spectral energy distribution of the intermediate blazar GC 0109+224
• Statistical properties of Faraday rotation measure in external galaxies -- I: intervening disc galaxies
• An insight into the extragalactic transient and variable microJy radio sky across multiple decades
• Millijansky Radio Variability in SDSS Stripe 82
• The University of Michigan Centimeter-Band All Stokes Blazar Monitoring Program: Single-Dish Polarimetry as a Probe of Parsec-Scale Magnetic Fields
• Optical variability power spectrum analysis of blazar sources on intranight timescales
• Two-sided radio emission in ON231 (W Comae)
• Interferometric Monitoring of Gamma-ray Bright AGNs: OJ 287
• A Quasi-Periodic Modulation of the Radio Light Curve of the Blazar PKS B0048-097
• Optical variability of radio-intermediate quasars
• Optical and Radio monitoring of S5 1803+74
• The jets-accretion relation, mass-luminosity relation in Fermi blazars
• Simultaneous spectra and radio properties of BL Lac's
• VSOP monitoring of the compact BL Lac object AO 0235+164
• Kinematic study of the parsec-scale jet of the quasar PKS 1741--03
• High frequency VLBI observations of the scatter broadened quasar B2005+403
• Multiwavelength Variability Analysis of the Blazar PKS 0727-11: A $\sim$168 Days Quasi-periodic Oscillation in Gamma-ray
• Sun-related variability in the light curves of compact radio sources. A new view on Extreme Scattering Events
• Identifying changing jets through their radio variability