New Tests of Milli-lensing in the Blazar PKS 1413 + 135

Creators: Peirson, A. L.; Liodakis, I.; Readhead, A. C. S.; Lister, M. L.; Perlman, E. S.; Aller, M. F.; Blandford, R. D.; Grainge, K. J. B.; Green, D. A.; Gurwell, M. A.; Hodges, M. W.; Hovatta, T.; Kiehlmann, S.; Lähteenmäki, A.; Max-Moerbeck, W.; Mcaloone, T.; O'Neill, S.; Pavlidou, V.; Pearson, T. J.; Ravi, V.; Reeves, R. A.; Scott, P. F.; Taylor, G. B.; Titterington, D. J.; Tornikoski, M.; Vedantham, H. K.; Wilkinson, P. N.; Williams, D. T.; Zensus, J. A.

Abstract

Symmetric achromatic variability (SAV) is a rare form of radio variability in blazars that has been attributed to gravitational milli-lensing by a ∼10²–10⁵ M_⊙ mass condensate. Four SAVs have been identified between 1980 and 2020 in the long-term radio monitoring data of the blazar PKS 1413 + 135. We show that all four can be fitted with the same, unchanging, gravitational lens model. If SAV is due to gravitational milli-lensing, PKS 1413 + 135 provides a unique system for studying active galactic nuclei with unprecedented microarcsecond resolution, as well as for studying the nature of the milli-lens itself. We discuss two possible candidates for the putative milli-lens: a giant molecular cloud hosted in the intervening edge-on spiral galaxy, and an undetected dwarf galaxy with a massive black hole. We find a significant dependence of SAV crossing time on frequency, which could indicate a fast shock moving in a slower underlying flow. We also find tentative evidence for a 989 day periodicity in the SAVs, which, if real, makes possible the prediction of future SAVs: the next three windows for possible SAVs begin in 2022 August, 2025 May, and 2028 February.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 August 22; revised 2021 November 25; accepted 2021 December 22; published 2022 March 2. The OVRO 40 m program was supported by private funding from the California Institute of Technology and the Max Planck Institute for Radio Astronomy, and by NASA grants NNG06GG1G, NNX08AW31G, NNX11A043G, and NNX13AQ89G from 2006 to 2016 and NSF grants AST-0808050, and AST-1109911 from 2008 to 2014. T.H. was supported by the Academy of Finland projects 317383, 320085, and 322535. S.K. acknowledges support from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program under grant agreement No. 771282. W.M. acknowledges support from ANID projects Basal AFB-170002 and PAI79160080. R.R. acknowledges support from ANID Basal AFB-170002, and ANID-FONDECYT grant 1181620. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. This research has used data from the University of Michigan Radio Astronomy Observatory, which has been supported by the University of Michigan and by a series of grants from the National Science Foundation, most recently AST-0607523, and from NASA-Fermi G. I. grants NNX09AU16G, NNX10AP16G, NNX13AP18G, and NNX11AO13G. The MOJAVE project was supported by NASA-Fermi grants 80NSSC19K1579, NNX15AU76G, and NNX12A087G. The Very Long Baseline Array and the National Radio Astronomy Observatory are facilities of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work made use of the Swinburne University of Technology software correlator (Deller et al. 2011), developed as part of the Australian Major National Research Facilities Programme and operated under licence. A.M.I. is supported by the Universities of Cambridge and Oxford, and acknowledges support from the European Research Council under grant ERC-2012-StG-307215 LODESTONE. Facilities: Metsähovi - , OVRO-40 m - , SMA - , UMRAO - , MRAO. -

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