A1 Vertaisarvioitu alkuperäisartikkeli tieteellisessä lehdessä
Polarisation angle variability in tidal disruption events
Tekijät: Floris, A.; Liodakis, I.; Koljonen, K. I. I.; Lindfors, E.; Agís-González, B.; Paggi, A.; Blinov, D.; Nilsson, K.; Agudo, I.; Charalampopoulos, P.; Escudero Pedrosa, J.; Piirola, V.
Kustantaja: EDP Sciences
Julkaisuvuosi: 2026
Lehti: Astronomy and Astrophysics
Artikkelin numero: A378
Vuosikerta: 707
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202557658
Julkaisun avoimuus kirjaamishetkellä: Avoimesti saatavilla
Julkaisukanavan avoimuus : Kokonaan avoin julkaisukanava
Verkko-osoite: https://doi.org/10.1051/0004-6361/202557658
Rinnakkaistallenteen osoite: https://research.utu.fi/converis/portal/detail/Publication/523443875
Rinnakkaistallenteen lisenssi: CC BY
Rinnakkaistallennetun julkaisun versio: Kustantajan versio
Context. Tidal disruption events (TDEs) occur when a star is disrupted by the tidal forces of a supermassive black hole, and these events produce bright multi-wavelength flares. Polarimetric measurements of TDEs allow us to disentangle the geometry and the mechanisms characterising the accretion process.
Aims. We carried out the first systematic study of the time evolution of the optical polarisation angle (Θ) in a sample of classified TDEs, combining our own data with all available measurements from the literature, with the goal of testing the currently available models that describe TDE emission.
Methods. We assembled data from all available observing epochs with significant linear polarisation detections (Π − 3σΠ > 0%) for sources with at least two such epochs, and we determined the overall variability trends across the sample in various time frames, such as days from peak time and the fallback time (t0) derived from the different models.
Results. Our final sample comprises 12 transients, including three Bowen fluorescence flares (BFFs). The majority of the sources show significant Θ variability. The distribution of |dΘ/dt| peaks near ∼2° d−1. BFFs tend to display sustained late-time Θ evolution, likely due in part to their slower fading. No universal trend emerges when time is normalised by t0.
Conclusions. Short-timescale Θ variability is common in TDEs and is difficult to reconcile with simple axisymmetric reprocessing models that predict a constant polarisation angle. The observed phenomenology favours scenarios with evolving, non-axisymmetric geometries and/or shocks, possibly coupled with changes in optical depth. Denser polarimetric monitoring, contemporaneous spectroscopy, and X-ray/UV coverage are required to break the remaining degeneracies.
Ladattava julkaisu This is an electronic reprint of the original article. |  |
Julkaisussa olevat rahoitustiedot:
AF, IL, AP and BAG were funded by the European Union ERC-2022-STG – BOOTES – 101076343. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. DB acknowledges support from the European Research Council (ERC) under the Horizon ERC Grants 2021 programme under grant agreement No. 101040021. KIIK has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 101002352, PI: M. Linares). Neither the European Union nor the granting authority can be held responsible for them. The IAA-CSIC co-authors acknowledge financial support from the Spanish “Ministerio de Ciencia e Innovación” (MCIN/AEI/ 10.13039/501100011033) through the Center of Excellence Severo Ochoa award for the Instituto de Astrofísica de Andalucía-CSIC (CEX2021-001131-S), and through grants PID2019-107847RB-C44 and PID2022-139117NB-C44. We acknowledge funding to support our NOT observations from the Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Finland (Academy of Finland grant nr 306531). E.L. was supported by Academy of Finland projects 317636 and 320045.
