Milliarcsecond core size dependence of the radio variability of blazars
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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en
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16
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Monthly Notices of the Royal Astronomical Society, Volume 525, issue 4, pp. 5105-5120
Abstract
Studying the long-term radio variability (time-scales of months to years) of blazars enables us to gain a better understanding of the physical structure of these objects on subparsec scales, and the physics of supermassive black holes. In this study, we focus on the radio variability of 1157 blazars observed at 15 GHz through the Owens Valley Radio Observatory Blazar Monitoring Program. We investigate the dependence of the variability amplitudes and time-scales, characterized based on model fitting to the structure functions, on the milliarcsecond core sizes measured by Very Long Baseline Interferometry. We find that the most compact sources at milliarcsecond scales exhibit larger variability amplitudes and shorter variability time-scales than more extended sources. Additionally, for sources with measured redshifts and Doppler boosting factors, the correlation between linear core sizes against variability amplitudes and intrinsic time-scales is also significant. The observed relationship between variability time-scales and core sizes is expected, based on light travel-time arguments. This variability versus core size relation extends beyond the core sizes measured at 15 GHz; we see significant correlation between the 15 GHz variability amplitudes (as well as time-scales) and core sizes measured at other frequencies, which can be attributed to a frequency-source size relationship arising from the intrinsic jet structure. At low frequencies of 1 GHz where the core sizes are dominated by interstellar scattering, we find that the variability amplitudes have significant correlation with the 1 GHz intrinsic core angular sizes, once the scatter broadening effects are deconvoluted from the intrinsic core sizes.Description
Funding Information: This research has made use of data from the OVRO 40-m monitoring program (Richards et al. ), supported by private funding from the California Institute of Technology and the Max Planck Institute for Radio Astronomy, and by NASA grants NNX08AW31G, NNX11A043G, and NNX14AQ89G and NSF grants AST-0808050 and AST-1109911. P.-C. H. is supported by the Taiwan National Science and Technology Council (NSTC, grant No. NSTC 111-2124-M-001-005 and NSTC 110-2124-M-001-007). T.H. was supported by the Academy of Finland projects 317383, 320085, 322535, and 345899. S.K. acknowledges support from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation programme under grant agreement no. 771282. W.M. gratefully acknowledges support by the ANID BASAL project FB210003 and FONDECYT 11190853. We are also grateful to the anonymous referee for the helpful comments that helped improve the manuscript. Publisher Copyright: © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
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Hsu, P-C, Koay, J Y, Matsushita, S, Hwang, C-Y, Hovatta, T, Kiehlmann, S, Readhead, A, Max-Moerbeck, W & Reeves, R 2023, 'Milliarcsecond core size dependence of the radio variability of blazars', Monthly Notices of the Royal Astronomical Society, vol. 525, no. 4, pp. 5105-5120. https://doi.org/10.1093/mnras/stad2525