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The presence of interstellar scintillation in the 15 GHz interday variability of 1158 OVRO-monitored blazars

Koay, J. Y. and Jauncey, D. L. and Hovatta, T. and Kiehlmann, S. and Bignall, H. E. and Max-Moerbeck, W. and Pearson, T. J. and Readhead, A. C. S. and Reeves, R. and Reynolds, C. and Vedantham, H. (2019) The presence of interstellar scintillation in the 15 GHz interday variability of 1158 OVRO-monitored blazars. Monthly Notices of the Royal Astronomical Society, 489 (4). pp. 5365-5380. ISSN 0035-8711. doi:10.1093/mnras/stz2488.

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We have conducted the first systematic search for interday variability in a large sample of extragalactic radio sources at 15 GHz. From the sample of 1158 radio-selected blazars monitored over an ∼10 yr span by the Owens Valley Radio Observatory 40-m telescope, we identified 20 sources exhibiting significant flux density variations on 4-d time-scales. The sky distribution of the variable sources is strongly dependent on the line-of-sight Galactic H α intensities from the Wisconsin H α Mapper Survey, demonstrating the contribution of interstellar scintillation (ISS) to their interday variability. 21 per cent of sources observed through sightlines with H α intensities larger than 10  rayleighs exhibit significant ISS persistent over the ∼10 yr period. The fraction of scintillators is potentially larger when considering less significant variables missed by our selection criteria, due to ISS intermittency. This study demonstrates that ISS is still important at 15 GHz, particularly through strongly scattered sightlines of the Galaxy. Of the 20 most significant variables, 11 are observed through the Orion–Eridanus superbubble, photoionized by hot stars of the Orion OB1 association. The high-energy neutrino source TXS 0506+056 is observed through this region, so ISS must be considered in any interpretation of its short-term radio variability. J0616−1041 appears to exhibit large ∼20 per cent interday flux density variations, comparable in magnitude to that of the very rare class of extreme, intrahour scintillators that includes PKS0405−385, J1819+3845, and PKS1257−326; this needs to be confirmed by higher cadence follow-up observations.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Koay, J. Y.0000-0002-7029-6658
Hovatta, T.0000-0002-2024-8199
Kiehlmann, S.0000-0001-6314-9177
Max-Moerbeck, W.0000-0002-5491-5244
Pearson, T. J.0000-0001-5213-6231
Readhead, A. C. S.0000-0001-9152-961X
Reynolds, C.0000-0002-1510-4860
Vedantham, H.0000-0002-0872-181X
Additional Information:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2019 September 3. Received 2019 September 1; in original form 2019 July 12. We thank the anonymous reviewer for the helpful suggestions to improve the manuscript. JYK thanks Keiichi Asada, Satoki Matsushita, Wen-Ping Lo, and Geoff Bower for helpful discussions. TH was supported by the Academy of Finland projects #317383 and #320085. WM and RR acknowledge support from CONICYT project Basal AFB-170002. This research has made use of data from the OVRO 40-m monitoring program (Richards et al. 2011) which is supported in part by the National Aeronautics and Space Administration (NASA) grants NNX08AW31G, NNX11A043G, and NNX14AQ89G and National Science Foundation (NSF) grants AST-0808050 and AST-1109911. The Wisconsin H α Mapper and its H α Sky Survey have been funded primarily by the NSF. The facility was designed and built with the help of the University of Wisconsin Graduate School, Physical Sciences Lab, and Space Astronomy Lab. National Optical Astronomy Observatory (NOAO) staff at Kitt Peak and Cerro Tololo provided on-site support for its remote operation.
Group:Astronomy Department
Funding AgencyGrant Number
Academy of Finland317383
Academy of Finland320085
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)UNSPECIFIED
Subject Keywords:scattering – ISM: general – galaxies: active – galaxies:jets – quasars: general – radio continuum: galaxies
Issue or Number:4
Record Number:CaltechAUTHORS:20191024-133301503
Persistent URL:
Official Citation:J Y Koay, D L Jauncey, T Hovatta, S Kiehlmann, H E Bignall, W Max-Moerbeck, T J Pearson, A C S Readhead, R Reeves, C Reynolds, H Vedantham, The presence of interstellar scintillation in the 15 GHz interday variability of 1158 OVRO-monitored blazars, Monthly Notices of the Royal Astronomical Society, Volume 489, Issue 4, November 2019, Pages 5365–5380,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99439
Deposited By: Tony Diaz
Deposited On:24 Oct 2019 20:44
Last Modified:16 Nov 2021 17:46

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