Revisiting the unification of tidal disruption events with polarimetry
Bibliographic record
Abstract
Aims . Tidal disruptions of stars by supermassive black holes produce emission at different wavelengths, but the optical emission is of ambiguous origin. A unification scenario of tidal disruption events (TDEs) has been proposed to explain the different classes of X-ray and optically selected events by introducing a dependence on the viewing angle and geometry. This work aims to test the unification scenario among optically bright TDEs using polarimetry. Methods. By studying the optical linear polarisation of nineteen TDEs (nine of which are newly analysed in this work), we placed constraints on their photosphere geometry, inclination, and the emission process responsible for the optical radiation. We also investigated how these properties correlate with the relative X-ray brightness of the events, quantified by the L X / L g ratio. Results. We find that 14 of the 16 non-relativistic events can be accommodated by the unification model. The continuum polarisation levels of the non-relativistic TDEs most often lie in the range P ∼ 1 − 2% (13 events), and for all except one event, they remain below 6%. For those optical TDEs that have multiple epochs of polarimetry, the continuum polarisation levels decrease with time after peak light for five of the ten events, increase for three events, and stay approximately constant for two events. When observed after +70 days (7/16 events), they become consistent with zero polarisation within uncertainties (5/7 events). This implies that the photosphere geometries of TDEs are at least initially asymmetric and evolve rapidly, which if tracing the formation of the accretion disc, suggests efficient circularisation. The polarisation signatures of emission lines of seven TDEs directly support a scenario in which optical light is reprocessed in an electron-scattering photosphere. TDEs are most often weak in X-rays when significantly polarised. However, a subset of events deviates from the unification model to some extent, suggesting this model may not fully capture the diverse behaviour of TDEs. Multi-epoch polarimetry plays a key role in understanding the evolution and emission mechanisms of TDEs.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.007 | 0.015 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.003 |
| Scholarly communication | 0.005 | 0.004 |
| Open science | 0.001 | 0.006 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".