A1 Refereed original research article in a scientific journal
The extreme coronal line emitter AT 2022fpx: varying optical polarization properties and late-time X-ray flare
Authors: Koljonen, Karri I.I.; Liodakis, Ioannis; Lindfors, Elina; Nilsson, Kari; Reynolds, Thomas M.; Charalampopoulos, Panos; Kouroumpatzakis, Konstantinos; McCall, Callum; Jermak, Helen E.; Steele, Iain A.; Carbajo-Hijarrubia, Juan
Publisher: Oxford University Press
Publication year: 2024
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: Monthly Notices of the Royal Astronomical Society
Volume: 532
Issue: 1
First page : 112
Last page: 125
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/stae1466
Web address : https://doi.org/10.1093/mnras/stae1466
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/457146342
Preprint address: https://arxiv.org/abs/2403.04877
Supermassive black holes disrupt passing stars, producing outbursts called tidal disruption events (TDEs). TDEs have recently gained attention due to their unique dynamics and emission processes, which are still not fully understood. Especially, the so-called optical TDEs are of interest as they often exhibit delayed or obscured X-ray emission from the accretion disc, making the origin of the prompt emission unclear. In this paper, we present multiband optical polarization observations and optical spectrometry of a recent TDE candidate AT 2022fpx, alongside monitoring observations in optical, ultraviolet, and X-rays. The optical spectra of AT 2022fpx show Bowen fluorescence as well as highly ionized iron emission lines, which are characteristic of extreme coronal line emitters. Additionally, the source exhibits variable but low-polarized continuum emission at the outburst peak, with a clear rotation of the polarization angle. X-ray emission observed approximately 250 d after the outburst peak in the decay appear flare-like but is consistent with constant temperature blackbody emission. The overall outburst decay is slower than for typical TDEs, and resembles more the ones seen from Bowen fluorescence flares. These observations suggest that AT 2022fpx could be a key source in linking different long-lived TDE scenarios. Its unique characteristics, such as extreme coronal line emission, variable polarization, and delayed X-ray flare, can be attributed to the outer shock scenario or a clumpy torus surrounding the supermassive black hole. Further studies, especially in the context of multiwavelength observations, are crucial to fully understand the dynamics and emission mechanisms of these intriguing astrophysical events.
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Funding information in the publication:
Research funded by European Research Council (101002352) | Academy of Finland (306531,317636,320045,346071) | Czech Science Foundation (22-22643S) | MINECO (ESP2016-80079-C2-1-R)
