Time-correlation between the radio and gamma-ray activity in blazars and the production site of the gamma-ray emission

Abstract

In order to determine the location of the gamma-ray emission site in blazars, we investigate the time-domain relationship between their radio and gamma-ray emission. Light-curves for the brightest detected blazars from the first 3 years of the mission of the Fermi Gamma-ray Space Telescope are cross-correlated with 4 years of 15GHz observations from the OVRO 40-m monitoring program. The large sample and long light-curve duration enable us to carry out a statistically robust analysis of the significance of the cross-correlations, which is investigated using Monte Carlo simulations including the uneven sampling and noise properties of the light-curves. Modeling the light-curves as red noise processes with power-law power spectral densities, we find that only one of 41 sources with high quality data in both bands shows correlations with significance larger than 3-sigma (AO 0235+164), with only two more larger than even 2.25-sigma (PKS 1502+106 and B2 2308+34). Additionally, we find correlated variability in Mrk 421 when including a strong flare that occurred in July-September 2012. These results demonstrate very clearly the difficulty of measuring statistically robust multiwavelength correlations and the care needed when comparing light-curves even when many years of data are used. This should be a caution. In all four sources the radio variations lag the gamma-ray variations, suggesting that the gamma-ray emission originates upstream of the radio emission. Continuous simultaneous monitoring over a longer time period is required to obtain high significance levels in cross-correlations between gamma-ray and radio variability in most blazars.

arXiv comment8 pages, 3 figures and 2 tables. Accepted for publication in MNRAS

References in corpus (33)

• Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• Fermi Large Area Telescope Second Source Catalog
• The Second Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• 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
• MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VI. Kinematics Analysis of a Complete Sample of Blazar Jets
• Measuring the broadband power spectra of active galactic nuclei with RXTE
• Doppler factors, Lorentz factors and viewing angles for quasars, BL Lacertae objects and radio galaxies
• The First Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• Comptonization of Infrared Radiation from Hot Dust by Relativistic Jets in Quasars
• Sub-milliarcsecond Imaging of Quasars and Active Galactic Nuclei. IV. Fine Scale Structure
• Gamma-ray Light Curves and Variability of Bright Fermi-Detected Blazars
• A change in the optical polarization associated with a gamma-ray flare in the blazar 3C 279
• The Structure of the M87 Jet: A Transition from Parabolic to Conical Streamlines
• CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates
• Jet opening angles and gamma-ray brightness of AGN
• On the Reliability of Cross Correlation Function Lag Determinations in Active Galactic Nuclei
• Location of gamma-ray Flare Emission in the Jet of the BL Lacertae Object OJ287 more than 14pc from the Central Engine
• Correlated Multi-Waveband Variability in the Blazar 3C~279 from 1996 to 2007
• On the relation between AGN gamma-ray emission and parsec-scale radio jets
• Multi-Epoch VLBA Observations of EGRET-Detected Quasars and BL Lac Objects: Connection between Superluminal Ejections and Gamma-Ray Flares in Blazars
• Detection of significant cm to sub-mm band radio and gamma-ray correlated variability in Fermi bright blazars
• The radio/gamma-ray connection in Active Galactic Nuclei in the era of the Fermi Large Area Telescope
• Correlated long-term optical and X-ray variations in NGC 5548
• 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
• Correlated X-ray/Optical Variability in the Quasar MR2251-178
• Radio/gamma-ray time delay in the parsec-scale cores of active galactic nuclei
• The first Fermi multifrequency campaign on BL Lacertae: characterizing the low-activity state of the eponymous blazar
• High-frequency radio properties of sources in the Fermi-LAT 1-year Point Source Catalogue
• VLBA monitoring of Mrk 421 at 15 GHz and 24 GHz during 2011
• Assessing the Significance of Apparent Correlations Between Radio and Gamma-ray Blazar Fluxes
• Correlation between Fermi/LAT gamma-ray and 37 GHz radio properties of northern AGN averaged over 11 months

Cited by in corpus (95)

• Relativistic Jets in Active Galactic Nuclei
• Active Galactic Nuclei: what's in a name?
• Kinematics of Parsec-Scale Jets of Gamma-Ray Blazars at 43~GHz within the VLBA-BU-BLAZAR Program
• Multiwavelength Evidence for Quasi-periodic Modulation in the Gamma-ray Blazar PG 1553+113
• Multiwavelength Study of Quiescent States of Mrk 421 with Unprecedented Hard X-Ray Coverage Provided by NuSTAR in 2013
• Kinematics of Parsec-Scale Jets of Gamma-Ray Bright Blazars at 43 GHz during Ten Years of the VLBA-BU-BLAZAR Program
• Long-term optical monitoring of TeV emitting Blazars
• Characterizing the Gamma-Ray Variability of the Brightest Flat Spectrum Radio Quasars Observed with the Fermi LAT
• Gamma rays from the quasar PKS 1441+25: story of an escape
• Temporal Correlations Between Optical and Gamma-ray Activity in Blazars
• Multiwavelength Cross-Correlations and Flaring Activity in Bright Blazars
• 4.5 years multi-wavelength observations of Mrk 421 during the ARGO-YBJ and Fermi common operation time
• Locating the gamma-ray emission site in Fermi/LAT blazars from correlation analysis between 37 GHz radio and gamma-ray light curves
• Multifrequency Photo-polarimetric WEBT Observation Campaign on the Blazar S5 0716+714: Source Microvariability and Search for Characteristic Timescales
• Magnetoluminescence
• A combined radio and GeV gamma-ray view of the 2012 and 2013 flares of Mrk 421
• Long-term study of Mkn 421 with the HAGAR Array of Telescopes
• Long-term multi-wavelength variability and correlation study of Markarian 421 from 2007 to 2009
• Multiwavelength observations of the blazar BL Lacertae: a new fast TeV gamma-ray flare
• Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and $\gamma$-ray activity in 2015$-$2016
• Proton Synchrotron $\gamma$-rays and the Energy Crisis in Blazars
• Exploring the nature of broadband variability in the FSRQ 3C 273
• Bimodal radio variability in OVRO-40m-monitored blazars
• A ring accelerator? Unusual jet dynamics in the IceCube candidate PKS 1502+106
• Testing two-component models on very-high-energy gamma-ray emitting BL Lac objects
• Multiwavelength periodicity search in a sample of $\gamma$-ray bright blazars
• Multi-messenger characterization of Mrk 501 during historically low X-ray and $\gamma$-ray activity
• Gamma-ray observations of low-luminosity active galactic nuclei
• A decade of joint MOJAVE-Fermi AGN monitoring: localisation of the gamma-ray emission region
• Locating the gamma-ray emission site in Fermi/LAT blazars. II Multifrequency correlations
• What can the 2008/10 broadband flare of PKS 1502+106 tell us? Nuclear opacity, magnetic fields, and the location of gamma rays
• Multiwavelength variability study and search for periodicity of PKS 1510-089
• H.E.S.S. detection of very-high-energy gamma-ray emission from the quasar PKS 0736+017
• Locating the gamma-ray emission region in the brightest Fermi-LAT Flat Spectrum Radio Quasars
• Radio$-\gamma -$ray response in blazars as a signature of adiabatic blob expansion
• Blazar variability power spectra from radio up to TeV photon energies: Mrk 421 and PKS 2155-304
• Exploring the origin of multiwavelength activities of high-redshift FSRQ PKS 1502+106 during 2014-2018
• Gaussian Process Modeling Blazar Multiwavelength Variability: Indirectly Resolving Jet Structure
• Resolving the High Energy Universe with Strong Gravitational Lensing: The Case of PKS 1830-211
• A multiband study and exploration of the radio wave - $\gamma$-ray connection in 3C 84
• Modelling blazar flaring using a time-dependent fluid jet emission model - an explanation for orphan flares and radio lags
• Multi-band Variability Analysis of Mrk 421
• A revised lens time delay for JVAS B0218+357 from a reanalysis of VLA monitoring data
• Curvature induced polarization and spectral index behavior for PKS 1502+106
• A Radio Quasi-periodic Oscillation of 176 day in the Radio-loud Narrow-line Seyfert 1 Galaxy J0849+5108
• The long-term centimeter variability of active galactic nuclei: A new relation between variability timescale and accretion rate
• Multi-band Variability of the TeV Blazar PG 1553+113 with XMM-Newton
• Gravitational Lenses as High-Resolution Telescopes
• The relentless variability of Mrk 421 from the TeV to the radio
• A comprehensive study on the variation phenomena of AO 0235+164
• Discovery of $\gamma$-ray emission from the radio-intermediate quasar III Zw 2: violent jet activity with intraday $\gamma$-ray variability
• Blazar Variability From Turbulence in Jets Launched by Magnetically Arrested Accretion Flows
• Constraints on the location of $\gamma$-ray emitting region for a sample of blazars with radio core-shift measurements
• Periodic Gamma-ray Modulation of the blazar PG 1553+113 Confirmed by Fermi-LAT and Multi-wavelength Observations
• The MASIV Survey IV: relationship between intra-day scintillation and intrinsic variability of radio AGNs
• Radio follow-up of the gamma-ray flaring gravitational lens JVAS B0218+357
• Exploring Short-Term Optical Variability of Blazars Using $\text{TESS}$
• Long-term multi-wavelength study of 1ES 0647+250
• Broadband study of OQ 334 during its flaring state
• Exploring the Nature of the 2016 γ-ray Emission in the Blazar 1749+096
• A flat-spectrum flare in S4 0444+63 revealed by a new implementation of multi-wavelength single-dish observations
• The hunt for extraterrestrial high-energy neutrino counterparts
• Multi-year characterisation of the broad-band emission from the intermittent extreme BL Lac 1ES~2344+514
• Locations of optical and $\gamma$-ray emitting regions in the jet of PMN J2345-1555
• The presence of interstellar scintillation in the 15 GHz interday variability of 1158 OVRO-monitored blazars
• Long-term multi-band photometric monitoring of Mrk 501
• Temporal variability and estimation of jet parameters for Ton 599
• Signatures of the disk-jet coupling in the Broad-line Radio Quasar 4C+74.26
• Interpreting the variation phenomena of B2 1633+382 via the two-component model
• Multiwavelength flaring activity of PKS1510-089
• Multi-wavelength temporal variability of the blazar PKS 1510-089
• Multiwavelength variability of the blazar AO 0235+164
• Detecting the Elusive Blazar Counter-Jets
• The relativistic parsec-scale jets of the blazars TXS 0506+056 and PKS 0502+049 and their possible association with gamma-ray flares and neutrino production
• Gamma-ray flares and broadband spectral study of PKS 0402-362
• Constraining the Physical Conditions in the Jets of Gamma-ray Flaring Blazars using Centimeter-Band Polarimetry and Radiative Transfer Simulations. II. Exploring Parameter Space and Implications
• Hunting for neutrino emission from multi-frequency variable sources
• On the connection of radio and $\gamma$-ray emission in blazars
• Estimating the distribution of rest-frame timescales for blazar jets: a statistical approach
• Bridging the Ultraviolet and Optical Regions: Transformation Equations between {\it GALEX} and {\it UBV} Photometric Systems
• Multiwavelength analysis of brightness variations of 3C~279: Probing the relativistic jet structure and its evolution
• Polarization Studies in Different Blazar Types. Part I: Correlation between Optical Brightness and Polarization Degree
• Revisiting Correlations Between Broad-Line and Jet Emission Variations for AGNs: 3C 120 and 3C 273
• Investigating Possible Correlations between Gamma-Ray and Optical Lightcurves for TeV-Detected Northern Blazars over 8 Years of Observations
• A numerical study on the role of instabilities on multi-wavelength emission signatures of blazar jets
• Estimating longterm power spectral densities in AGN from simulations
• Multi-messenger emission from the parsec-scale jet of the flat-spectrum radio quasar PKS 1502+106 coincident with high-energy neutrino IceCube-190730A
• Multiwavelength Variability Analysis of the Blazar PKS 0727-11: A $\sim$168 Days Quasi-periodic Oscillation in Gamma-ray
• Optical Monitoring and Long-term Optical Spectral Variability of BL Lacertae Object S5 0716+714
• GeV-radio correlation in Markarian 421
• Gamma-ray flares from the jet of the blazar CTA 102 in 2016-2018
• The connection between the 15 GHz radio and gamma-ray emission in blazars
• Multi wavelength study of 4C+28.07
• Testing X-ray Periodicity and Long-Term Trend in PG 1553+113 via Targeted Swift-XRT Monitoring
• Pinpointing the location of the gamma-ray emitting region in the FSRQ 4C+01.28