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Bimodal radio variability in OVRO-40 m-monitored blazars

Liodakis, I. and Pavlidou, V. and Hovatta, T. and Max-Moerbeck, W. and Pearson, T. J. and Richards, J. L. and Readhead, A. C. S. (2017) Bimodal radio variability in OVRO-40 m-monitored blazars. Monthly Notices of the Royal Astronomical Society, 467 (4). pp. 4565-4576. ISSN 0035-8711. doi:10.1093/mnras/stx432.

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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 γ-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) γ-ray detected differ from the γ-ray non-detected sources in all their variability properties, suggesting a link between the production of γ-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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Liodakis, I.0000-0001-9200-4006
Hovatta, T.0000-0002-2024-8199
Max-Moerbeck, W.0000-0002-5491-5244
Pearson, T. J.0000-0001-5213-6231
Readhead, A. C. S.0000-0001-9152-961X
Additional Information:© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Received 30 November 2016; revision received 16 February 2017; accepted 16 February 2017; published 20 February 2017. The authors would like to thank the referee Hayley Bignall and Vassilis Karamanavis for constructive comments and suggestions that helped improve this work. IL thanks the Caltech Astronomy Department for their hospitality during the completion of this work. This research was supported by the European Commission Seventh Framework Program (FP7) through grants PCIG10-GA-2011-304001 ‘JetPop’ and PIRSES-GA-2012-31578 ‘EuroCal’. TH was supported in part by the Academy of Finland project number 267324. This research has made use of data from the OVRO 40 m monitoring programme (Richards et al. 2011) that is supported in part by NASA grants NNX08AW31G, NNX11A043G and NNX14AQ89G and NSF grants AST-0808050 and AST-1109911.
Group:Astronomy Department
Funding AgencyGrant Number
Marie Curie FellowshipPCIG10-GA-2011-304001
European Research Council (ERC)PIRSES-GA-2012-31578
Academy of Finland267324
Subject Keywords:Methods: statistical; Galaxies: active; Galaxies: jets
Issue or Number:4
Record Number:CaltechAUTHORS:20170428-112807505
Persistent URL:
Official Citation:I. Liodakis, V. Pavlidou, T. Hovatta, W. Max-Moerbeck, T. J. Pearson, J. L. Richards, A. C. S. Readhead; Bimodal radio variability in OVRO-40 m-monitored blazars. Mon Not R Astron Soc 2017; 467 (4): 4565-4576. doi: 10.1093/mnras/stx432
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77056
Deposited By: Melissa Ray
Deposited On:28 Apr 2017 18:55
Last Modified:15 Nov 2021 17:05

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