A1 Refereed original research article in a scientific journal
Detection of quasi-periodic oscillations in the 37 GHz radio light curve of the blazar Ton 599 during 1990–2020
Authors: Gupta, Alok C.; Volvach, Alexandr E.; Kishore, Shubham; Volvach, Larisa N.; Wiita, Paul J.; Cui, Lang; Valtonen, Mauri J.; Mondal, Sandeep K.; Gaur, Haritma
Publisher: EDP Sciences
Publication year: 2026
Journal: Astronomy and Astrophysics
Article number: A371
Volume: 707
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202557403
Publication's open availability at the time of reporting: Open Access
Publication channel's open availability : Open Access publication channel
Web address : https://doi.org/10.1051/0004-6361/202557403
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/523441568
Self-archived copy's licence: CC BY
Self-archived copy's version: Publisher`s PDF
Context. Blazars are a subclass of radio-loud active galactic nuclei (AGN) that display strong multi-wavelength variability on diverse timescales ranging from years down to minutes. In the last 1.5 decades, there have been occasional detections of quasi-periodic oscillations in several blazars in their time series data.
Aims. We searched for quasi-periodic oscillations (QPOs) in the 37 GHz radio band light curve of the flat-spectrum radio quasar Ton 599 made at the RT-22 radio telescope in Simeiz, Crimea, from 1990 to 2020. We also searched for QPOs in the available gamma-ray and optical data during the time span of these radio observations.
Methods. To identify and quantify the QPO nature of this radio light curve of Ton 599, we used the Lomb–Scargle periodogram (LSP), REDFIT, and weighted wavelet Z-transform (WWZ) analyses. We performed LSP analyses of the gamma-ray and optical data.
Results. We report the detection of a likely QPO of about 2.4 years in a portion of the 37 GHz radio light curve of Ton 599. No QPO signatures of similar timescales were found in either the γ-ray or optical (R-band) wavebands.
Conclusions. We briefly discuss possible emission models for radio-loud AGN that could explain such QPOs with periods of a few years.
Downloadable publication This is an electronic reprint of the original article. |  |
Funding information in the publication:
This work was supported by the CAS ‘Light of West China’ Program with Grant No. 2021-XBQNXZ-005. ACG is partially supported by the CAS ‘President’s International Fellowship Initiative (PIFI)’ with Grant No. 2026PVA0040. LC acknowledges the support from the Tianshan Talent Training Program with Grant No. 2023TSYCCX0099. HG acknowledges the financial support from Science and Engineering Research (SERB), India, through SERB Research Scientist award SB/SRS/2022-23/113/PS at ARIES, Nainital, India.
