A1 Refereed original research article in a scientific journal
Spectropolarimetry of a Nuclear Transient AT2023clx: Revealing the Geometrical Alignment between the Transient Outflow and the Nuclear Dusty Region
Authors: Uno, Kohki; Maeda, Keiichi; Nagao, Takashi; Leloudas, Giorgos; Charalampopoulos, Panos; Mattila, Seppo; Aoki, Kentaro; Taguchi, Kenta; Kawabata, Miho; Moldon, Javier; Perez-Torres, Miguel; Pursiainen, Miika; Reynolds, Thomas
Publisher: Institute of Physics Publishing Ltd.
Publishing place: BRISTOL
Publication year: 2025
Journal: Astrophysical Journal Letters
Journal name in source: The Astrophysical Journal Letters
Journal acronym: ASTROPHYS J LETT
Article number: L23
Volume: 986
Issue: 2
Number of pages: 11
ISSN: 2041-8205
eISSN: 2041-8213
DOI: https://doi.org/10.3847/2041-8213/add71b
Web address : https://doi.org/10.3847/2041-8213/add71b
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/499183602
AT2023clx, which occurred in NGC 3799 with a low-ionization nuclear emission-line region (LINER), is one of the most nearby nuclear transients classified as a tidal disruption event (TDE). We present three-epoch spectropolarimetric follow-up observations of AT2023clx. We detected two polarization components; one is a constant polarization of similar to 1% originating from an aspherical outflow associated with the transient, while the other is a blue-excess polarization toward similar to 2% originating from a nuclear dusty environment via light echoes. The polarization angle flipped by 90 degrees between the two epochs, indicating that the outflow direction was perpendicular to the dust plane. Furthermore, the polarized flux might suggest that the nuclear dust favors relatively large grains, potentially offering constraints on its physical properties. Such polarization features-the blue excess and the 90 degrees flip-have never been observed in previous TDE polarization samples, highlighting unique mechanisms behind AT2023clx. We propose possible scenarios: the disruption of a star formed within or captured by a nuclear dusty cloud. Given the LINER nature of NGC3799, the dusty region may possibly be linked to a torus or disk associated with a weak active galactic nucleus (AGN). Furthermore, as a more speculative scenario, the event might have been triggered by AGN-like activity, potentially linked to changing-look AGNs or ambiguous nuclear transients. These findings highlight the power of time-series spectropolarimetry of TDEs, not only in probing the origins of nuclear transients but also in investigating the physical properties of nuclear dust.
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This research is based on observations obtained at the Subaru Telescope (S23A-052, PI: K.U.) operated by the National Astronomical Observatory of Japan (NAOJ), the Seimei Telescope at the Okayama observatory of Kyoto University (23A-K-0001, PI: K.M.), the Nordic Optical Telescope (66-019, PI: P.C.), and e-MERLIN (DD16004, PI: M.P.-T.). The Seimei telescope is jointly operated by Kyoto University and the NAOJ, with assistance provided by the Optical and Near-Infrared Astronomy Inter-University Cooperation Program. The spectra taken by the Seimei telescope are obtained with the KASTOR (Kanata And Seimei Transient Observation Regime) campaign. The authors thank Mitsuru Kokubo, Takeo Minezaki, and Jason T. Hinkle for valuable discussions. K.U. acknowledges financial support from Grant-in-Aid for the Japan Society for the Promotion of Science (JSPS) Fellows (22J22705 and 22KJ1986), and support from the Hayakawa Satio Fund awarded by the Astronomical Society of Japan. K.M. acknowledges support from JSPS KAKENHI grant Nos. JP20H00174, JP20H04737, JP24H01810, and JP24KK0070, and support from the JSPS Open Partnership Bilateral Joint Research Projects between Japan and Finland (JPJSBP120229923). T.N. acknowledges support from the Research Council of Finland projects 324504, 328898, and 353019. G.L. was supported by a research grant (19054) from VILLUM FONDEN. P.C. acknowledges support via Research Council of Finland (grant 340613). S.M. was funded by the Academy of Finland project 350458. J.M. and M.P.-T. acknowledge financial support from the grant CEX2021-001131-S funded by MICIN/AEI/ 10.13039/501100011033. J.M. acknowledges financial support from the grant PID2021-123930OB-C21 funded by MICIN/AEI/ 10.13039/501100011033, by "ERDF A way of making Europe," and by the "European Union". J.M. and M.P.-T. acknowledges financial support through grant PID2023-147883NB-C21, funded by MCIN/AEI/ 10.13039/501100011033. J.M. acknowledges the Spanish Prototype of an SRC (SPSRC) service and support funded by the Spanish Ministry of Science, Innovation and Universities, by the Regional Government of Andalusia, by the European Regional Development Funds, and by the European Union NextGenerationEU/PRTR. The SPSRC acknowledges financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709) and from the grant CEX2021-001131-S funded by MICIN/AEI/ 10.13039/501100011033. e-MERLIN is a National Facility operated by the University of Manchester at Jodrell Bank Observatory on behalf of STFC. M.P. acknowledges support from a UK Research and Innovation Fellowship (MR/T020784/1). T.R is part of the Cosmic Dawn Center (DAWN), which is funded by the Danish National Research Foundation under grant DNRF140. T.R acknowledges support from the Research Council of Finland project 350458. The data within this Letter will be available on the Weizmann Interactive Supernova Data Repository (WISeREP) or upon reasonable request to the corresponding authors.
