Bimodal radio variability in OVRO-40 m-monitored blazars

I. Liodakis*, V. Pavlidou, T. Hovatta, W. Max-Moerbeck, T. J. Pearson, J. L. Richards, A.C.S. Readhead

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

10 Citations (Scopus)
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Abstract

Blazars are known to show periods of quiescence followed by outbursts visible throughout the electromagnetic spectrum. We present a novel maximum likelihood approach to capture this bimodal behaviour by examining blazar radio variability in the flux-density domain. We separate quiescent and flaring components of a source's light curve by modelling its flux-density distribution as a series of 'off'- and 'on'-states. Our modelling allows us to extract information regarding the flaring ratio, duty cycle, and the modulation index in the 'off'state, in the 'on'- state, as well as throughout the monitoring period of each blazar. We apply our method to a flux-density-limited subsample from the Owens Valley Radio Observatory's 15 GHz blazar monitoring programme, and explore differences in the variability characteristics between BL Lacs and FSRQs as well as between gamma-ray detected and non-detected sources. We find that (1) BL Lacs are more variable and have relatively larger outbursts than the FSRQs; (2) unclassified blazar candidates in our sample show similar variability characteristics as the FSRQs and (3) gamma-ray detected differ from the gamma-ray non-detected sources in all their variability properties, suggesting a link between the production of gamma-rays and the mechanism responsible for the radio variability. Finally, we fit distributions for blazar flaring ratios, duty cycles, and on- and off-modulation indices that can be used in population studies of variability-dependent blazar properties.

Original languageEnglish
Pages (from-to)4565-4576
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Volume467
Issue number4
DOIs
Publication statusPublished - Jun 2017
MoE publication typeA1 Journal article-refereed

Keywords

  • methods: statistical
  • galaxies: active
  • galaxies: jets
  • ACTIVE GALACTIC NUCLEI
  • FLUX-DENSITY VARIATIONS
  • BL LACERTAE OBJECTS
  • GAMMA-RAY ACTIVITY
  • OPTICAL POLARIZATION
  • LORENTZ FACTORS
  • VIEWING ANGLES
  • INNER JET
  • ROBOPOL
  • EMISSION

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