Multiwavelength Variability Power Spectrum Analysis of the Blazars 3C 279 and PKS 1510–089 on Multiple Timescales

Creators: Goyal, Arti; Soida, Marian; Stawarz, Łukasz; Wiita, Paul J.; Nilsson, Kari; Jorstad, Svetlana; Marscher, Alan P.; Aller, Margo F.; Aller, Hugh D.; Lähteenmäki, Anne; Hovatta, Talvikki; Zoła, Staszek; Nalewajko, Krzysztof; Tornikoski, Merja; Tammi, Joni; Hodges, Mark; Kiehlmann, Sebastian; Readhead, Anthony C. S.; Max-Moerbeck, Walter; Lindfors, Elina; Fallah Ramazani, Vandad; Reichart, D. E.; Caton, D. B.; Valverde, Janeth; Horan, Deirdre; Ojha, Roopesh; van Zyl, Pfesesani

Abstract

We present the results of variability power spectral density (PSD) analysis using multiwavelength radio to GeV γ-ray light curves covering timescales of decades/years to days/minutes for the blazars 3C 279 and PKS 1510−089. The PSDs are modeled as single power laws, and the best-fit spectral shape is derived using the "power spectral response" method. With more than 10 yr of data obtained with weekly/daily sampling intervals, most of the PSDs cover ∼2–4 decades in temporal frequency; moreover, in the optical band, the PSDs cover ∼6 decades for 3C 279 due to the availability of intranight light curves. Our main results are the following: (1) on timescales ranging from decades to days, the synchrotron and the inverse-Compton spectral components, in general, exhibit red-noise (slope ∼2) and flicker-noise (slope ∼1) type variability, respectively; (2) the slopes of γ-ray variability PSDs obtained using a 3 hr integration bin and 3 weeks total duration exhibit a range between ∼1.4 and ∼2.0 (mean slope = 1.60 ± 0.70), consistent within errors with the slope on longer timescales; (3) comparisons of fractional variability indicate more power on timescales ≤100 days at γ-ray frequencies compared to longer wavelengths, in general (except between the γ-ray and optical wavelengths for PKS 1510−089); (4) the normalization of intranight optical PSDs for 3C 279 appears to be a simple extrapolation from longer timescales, indicating a continuous (single) process driving the variability at optical wavelengths; and (5) the emission at optical/infrared wavelengths may involve a combination of disk and jet processes for PKS 1510−089.

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 October 22; revised 2022 January 14; accepted 2022 January 19; published 2022 March 17. We thank the journal referee for insightful and constructive comments, which improved the clarity and content of the manuscript. We thank our internal Fermi-LAT reviewer, C. C. Cheung, for careful reading and several constructive comments on the manuscript. We also thank the Fermi-LAT publication board members, Philippe Bruel and Matthew Kerr, for useful comments. A.G. acknowledges the financial support from the Polish National Science Centre (NCN) through the grant 2018/29/B/ST9/02298. S.Z. acknowledges NCN grant 2018/29/B/ST9/01793. L. S. was supported by the Polish NSC grant 2016/22/E/ST9/00061. 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. A.G. acknowledges many discussions with FSSC help desk contact Nestor Mirabel regarding the LAT analysis. The Monte Carlo simulations of the light curves have been performed at the Prometheus cluster of the Cyfronet PL grid under the computing grants "lcsims2" and "plglcsims." A.G. thanks Michał Ostrowski, Marek Sikora, and Stefan Wagner for useful discussions on the manuscript. This research has used data from the University of Michigan Radio Astronomy Observatory, which was supported by the University of Michigan; research at this facility was supported in part by NSF grants AST-8021250, AST-8301234, AST-8501093, AST-8815678, AST-9120224, AST-9421979, AST-9617032, AST-9900723, AST-0307629, AST-0607523, and earlier awards, and by NASA under awards NNX09AU16G, NNX10AP16G, NNX11AO13G, and NNX13AP18G. This publication makes use of data obtained at Metsähovi Radio Observatory, operated by Aalto University in Finland. This research has made use of data from the OVRO 40 m monitoring program which was supported in part by NASA grants NNX08AW31G, NNX11A043G, and NNX14AQ89G, and NSF grants AST-0808050 and AST-1109911 and private funding from Caltech and the MPIfR. This paper has made use of up-to-date SMARTS optical/near-infrared light curves that are available at www.astro.yale.edu/smarts/glast/home.php. The research at Boston University was supported by a number of NASA Fermi Guest Investigator grants, most recently 80NSSC20K1567. The material is based upon work supported by NASA under award number 80GSFC21M0002. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat á l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National dÉtudes Spatiales in France. This work was performed in part under DOE Contract DE-AC02-76SF00515. Facilities: Fermi - Fermi Gamma-Ray Space Telescope (formerly GLAST), RXTE - , Swift - , SMARTS - , REM - , Tuorla - , VLBA-BU-BLAZAR - , SKYNET - , MRO - , OVRO - , UMRAO - .

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