Long-term radio variability of AGN: flare characteristics

Abstract

We have studied the flare characteristics of 55 AGN at 8 different frequency bands between 4.8 and 230 GHz. Our extensive database enables us to study the various observational properties of flares in these sources and compare our results with theoretical models. We visually extracted 159 individual flares from the flux density curves and calculated different parameters, such as the peak flux density and duration, in all the frequency bands. The selection of flares is based on the 22 and 37 GHz data from Metsähovi Radio Observatory and 90 and 230 GHz data from the SEST telescope. Additional lower frequency 4.8, 8, and 14.5 GHz data are from the University of Michigan Radio Observatory. We also calculated variability indices and compared them with earlier studies. The observations seem to adhere well to the shock model, but there is still large scatter in the data. Especially the time delays between different frequency bands are difficult to study due to the incomplete sampling of the higher frequencies. The average duration of the flares is 2.5 years at 22 and 37 GHz, which shows that long-term monitoring is essential for understanding the typical behaviour in these sources. It also seems that the energy release in a flare is independent of the duration of the flare.

11 pages, 9 figures, 2 tables, accepted for publication in A&A

References in corpus (3)

• Statistical analyses of long-term variability of AGN at high radio frequencies
• Synchrotron flaring in the jet of 3C 279
• Frequency-dependent time delays for strong outbursts in four blazars from the Metsahovi and UMRAO monitoring databases

Cited by in corpus (35)

• Doppler factors, Lorentz factors and viewing angles for quasars, BL Lacertae objects and radio galaxies
• The Spitzer Deep, Wide-Field Survey
• Radio Properties of Tidal Disruption Events
• Detection of significant cm to sub-mm band radio and gamma-ray correlated variability in Fermi bright blazars
• Radio/gamma-ray time delay in the parsec-scale cores of active galactic nuclei
• Comparative performance of selected variability detection techniques in photometric time series
• Radio observations of the tidal disruption event XMMSL1 J0740$-$85
• On the radio properties of the intermediate-mass black hole candidate ESO 243-49 HLX-1
• Radio Detection of VIK J2318$-$3113, the Most Distant Radio-Loud Quasar ($z$=6.44)
• Bimodal radio variability in OVRO-40m-monitored blazars
• The Gould's Belt Very Large Array Survey II: The Serpens region
• The connection between the parsec-scale radio jet and gamma-ray flares in the blazar 1156+295
• 21 new long-term variables in the GX 339-4 field: two years of MeerKAT monitoring
• The long-term centimeter variability of active galactic nuclei: A new relation between variability timescale and accretion rate
• Radio-interferometric monitoring of FRB 131104: A coincident AGN flare, but no evidence for a cosmic fireball
• An insight into the extragalactic transient and variable microJy radio sky across multiple decades
• The MASIV Survey IV: relationship between intra-day scintillation and intrinsic variability of radio AGNs
• Flux variability from ejectas in structured relativistic jets with large-scale magnetic fields
• A compact symmetric radio source born at one-tenth the current age of the Universe
• Variability and parsec-scale radio structure of candidate compact symmetric objects
• Magnetic Field Strengths of the Synchrotron Self-Absorption Region in the Jet of CTA 102 During Radio Flares
• The Radio Structure of the Narrow-Line Seyfert 1 Mrk 783 with VLBA and e-MERLIN
• A flat-spectrum flare in S4 0444+63 revealed by a new implementation of multi-wavelength single-dish observations
• Wide-Band Spectral Variability of Peaked Spectrum Sources
• Search and identification of transient and variable radio sources using MeerKAT observations: a case study on the MAXI J1820+070 field
• AGN torus emission for a homogeneous sample of bright FSRQs
• Interactions between the jet and disk wind in a nearby radio intermediate quasar III Zw 2
• A comprehensive long term study of the radio and X-ray Variability of NGC 4051 Paper II
• VLA/JVLA Monitoring of Bright Northern Radio Sources
• RadioSED I: Bayesian inference of radio SEDs from inhomogeneous surveys
• A procedure for making high dynamic-range radio images: Deep imaging of the kiloparsec-scale radio structures of a distant blazar, NRAO 530, with JVLA data
• A numerical study on the role of instabilities on multi-wavelength emission signatures of blazar jets
• VLBI Analysis of a Potential High-Energy Neutrino Emitter Blazar
• Magnetic Reconnection as a Potential Driver of X-ray Variability in Active Galactic Nuclei
• 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