Long-term Swift and Metsähovi monitoring of SDSS J164100.10+345452.7 reveals multi-wavelength correlated variability

Thumbnail Image
Access rights
Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Degree programme
Astronomy and Astrophysics, Volume 673
We report on the first multi-wavelength Swift monitoring campaign performed on SDSS J164100.10+345452.7, a nearby narrow-line Seyfert 1 galaxy that had formerly been considered to be radio-quiet. It has, however, more recently been detected both in the radio (at 37 GHz) and in the γ-ray, a behaviour that hints at the presence of a relativistic jet. During our 20-month Swift campaign, while pursuing the primary goal of assessing the baseline optical/UV and X-ray properties of SDSS J164100.10+345452.7, we observed two radio flaring episodes, namely, one each year. Our strictly simultaneous multi-wavelength data closely match the radio flare and allow us to unambiguously link the jetted radio emission of SDSS J164100.10+345452.7. Indeed, for the X-ray spectra preceding and following the radio flare, a simple absorbed power-law model does not offer an adequate description and, thus, an extra absorption component is required. The average spectrum of SDSS J164100.10+345452.7 can best be described by an absorbed power-law model with a photon index Σ = 1.93 ± 0.12, modified by a partially covering neutral absorber with a covering fraction of f = 0.91-0.03+0.02. On the contrary, the X-ray spectrum closest to the radio flare does not require any such extra absorber and it is much harder (Σflare ∼0.7 ± 0.4), thus implying the emergence of an additional, harder spectral component. We interpret this as the jet emission emerging from a gap in the absorber. The fractional variability we derived in the optical/UV and X-ray bands is found to be lower than the typical values reported in the literature because our observations of SDSS J164100.10+345452.7 are dominated by the source being in a low state, as opposed to the literature, where the observations were generally taken as a follow-up of bright flares in other energy bands. Based on the assumption that the origin of the 37 GHz radio flare is the emergence of a jet from an obscuring screen also observed in the X-ray, the derived total jet power is Pjettot = 3.5 × 1042 erg s-1. This result is close to the lowest values measured in the literature.
Funding Information: We thank the anonymous referee for comments that helped to improve the paper. We acknowledge unwavering support from Amos. This work has been partially supported by the ASI-INAF program I/004/11/4. We acknowledge financial contribution from the agreement ASI-INAF n. 2017-14-H.0. This publication makes use of data obtained at Metsähovi Radio Observatory, operated by Aalto University in Finland. We acknowledge the use of public data from the Swift data archive. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Part of this work is based on archival data, software or online services provided by the Space Science Data Center - ASI. Happy 18th, Swift Publisher Copyright: © The Authors 2023.
Galaxies: active, Galaxies: individual: SDSS J164100.10+345452.7, Galaxies: Seyfert, X-rays: individuals: SDSS J164100.10+345452.7
Other note
Romano, P, Lähteenmäki, A, Vercellone, S, Foschini, L, Berton, M, Raiteri, C M, Braito, V, Ciroi, S, Järvelä, E, Baitieri, S, Varglund, I, Tornikoski, M & Suutarinen, S 2023, ' Long-term Swift and Metsähovi monitoring of SDSS J164100.10+345452.7 reveals multi-wavelength correlated variability ', Astronomy and Astrophysics, vol. 673, A85 . https://doi.org/10.1051/0004-6361/202345936