A1 Refereed original research article in a scientific journal
Multiwavelength monitoring and reverberation mapping of NGC 2617 at deepest minimum with a sharp upward turn during 2021-2024
Authors: Oknyansky, V. L.; Brotherton, M. S.; Tsygankov, S. S.; Dodin, A. V; Tatarnikov, A. M.; Du, P.; Burlak, M. A.; Ikonnikova, N. P.; (Metlov, V. G.; Belinski, A. A.; Shatsky, N. I.; Wang, J. -M; (Bao, D. -W; Fang, F.; Zhai, S.; Fu, Y. -X; Bai, H. -R; Zastrocky, T. E.; Chelouche, D; Figaredo, C. Sobrino; Kaspi, S.; Gaskell, C. M.
Publisher: Oxford University Press
Publication year: 2025
Journal: Monthly Notices of the Royal Astronomical Society
Volume: 536
Issue: 3
First page : 2089
Last page: 2102
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/stae2707
Web address : https://doi.org/10.1093/mnras/stae2707
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/477535373
We present the results of a new X-ray to near-IR photometric and spectroscopic monitoring of the changing look active galactic nucleus NGC 2617 carried out from March 2022 to March 2024. We found significant variability at all wavelengths and in the intensities and profiles of the broad Balmer lines. Reverberation mapping was carried out for three observing seasons during 2021–2024. We obtained time delays of ∼4 d for the response of the H βline to optical continuum variations. The X-ray variations correlate well with the UV and optical, with a few days lag for longer wavelengths. The K band lagged the B band by ∼15 d during the last three seasons, which is significantly shorter than the delays reported previously by the 2016 and 2017–2019 campaigns. Near-IR variability arises from two different emission regions: the outer part of the accretion disc and a more distant dust component. The H K-band variability is go v erned primarily by dust. The H β/H αratio variations (for broad components only) correlate with the X-ray and UV fluxes. The spectral type changed from type 1.8 to type 1.9 during 2023 October–2024 January and then a more rapid change to type 1.5 occurred in 2024 February. We interpret these changes as a combination of two factors: changes in the accretion rate as a dominant cause but also the sublimation or reco v ery of dust along the line of sight.
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Funding information in the publication:
We thank A. Cherepashchuk for supporting our research and observations, and the staff of the observatories. We also express our thanks to the Swift administrators for approving the ToO observation requests and the Swift ToO team for promptly scheduling and executing our observations. We thank B. Shappee for sending us data in a digital format. We are grateful to H. Netzer and A. Laor for useful discussions. This work was supported in part by the M. V. Lomonosov Moscow State University Program of Development. This research has been partly supported by Israeli Science Foundation grants 2398/19, 1650/23, and by the Center for Integration in Science of the Ministry of Aliyah and Integration. We thank WIRO engineers Conrad Vogel and Andrew Hudson for their indispensable and invaluable assistance. M.S. Brotherton enjoyed support from the Chinese Academy of Sciences Presidents International Fellowship Initiative (grant 2018VMA0005). T.E. Zastrocky acknowledges support from NSF grant 1005444I. We thank H. Winkler and F. van Wyk as the data providers and the South African Astronomical Observatory (SAAO) for the allocation of telescope time and use of their facilities. P. Du acknowledges financial support from National Key R&D Program of China (2023YFA1607903 and 2021YFA1600404), from NSFC grants NSFC-12022301 and 11991051, and by the China Manned Space Project with no. CMS-CSST-2021-A06. J.-M. Wang acknowledges financial support from National Key R&D Program of China 2021YFA1600404, from NSFC grants NSFC 11991050, 11991054 and 12333003, and by the China Manned Space Project with no. CMS-CSST-2021-A06.
