A1 Refereed original research article in a scientific journal
New Tests of Milli-lensing in the Blazar PKS 1413+135
Authors: Peirson AL, Liodakis I, Readhead ACS, Lister ML, Perlman ES, Aller MF, Blandford RD, Grainge KJB, Green DA, Gurwell MA, Hodges MW, Hovatta T, Kiehlmann S, Lahteenmaki A, Max-Moerbeck W, Mcaloone T, O'Neill S, Pavlidou V, Pearson TJ, Ravi V, Reeves RA, Scott PF, Taylor GB, Titterington DJ, Tornikoski M, Vedantham HK, Wilkinson PN, Williams DT, Zensus JA
Publisher: IOP Publishing Ltd
Publication year: 2022
Journal: Astrophysical Journal
Journal name in source: ASTROPHYSICAL JOURNAL
Journal acronym: ASTROPHYS J
Article number: 24
Volume: 927
Issue: 1
Number of pages: 20
ISSN: 0004-637X
DOI: https://doi.org/10.3847/1538-4357/ac469e
Web address : https://iopscience.iop.org/article/10.3847/1538-4357/ac469e
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/174661984
Preprint address: https://arxiv.org/abs/2201.01110
Symmetric achromatic variability (SAV) is a rare form of radio variability in blazars that has been attributed to gravitational milli-lensing by a similar to 10(2)-10(5) M (circle dot) 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.
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