Observational diversity of bright long-lived Type II supernovae
Bibliographic record
Abstract
Context. In various types of supernovae (SNe), strong interaction between the SN ejecta and circumstellar material (CSM) has been reported. This raises questions about their progenitors and mass-loss processes shortly before the explosion. Recently, the bright long-lived Type II SN 2021irp was proposed to be a standard Type II SN interacting with disk-like CSM. The observational properties suggest that the progenitor was a massive star (∼8−18 M⊙) in a binary system and underwent a mass-ejection process due to the binary interaction just before the explosion. Similar scenarios, i.e., a Type II SN interacting with a CSM disk, have also been invoked to explain some Type IIn SNe. Aims. Here, we study the diversity of the observational properties of bright long-lived Type II (21irp-like) SNe. We analyze the diversity of their CSM properties, in order to understand their progenitors and mass-loss mechanisms and their relations with the other types of interacting SNe. Methods. We performed photometry, spectroscopy, and/or polarimetry for four 21irp-like SNe. Based on these observations as well as published data of SN 2021irp itself and well-observed bright and long-lived type II SNe including SNe 2010jl, 2015da, and 2017hcc, we discuss their CSM characteristics. Results. This sample of SNe shows luminous and long-lived photometric evolution, with some variations in the photometric evolution (from ∼−17 to ∼−20 absolute mag in the r/o band even at ∼200 days after the explosion). They show photospheric spectra characterized mainly by Balmer lines for several hundreds of days, with some variations in the shapes of the lines. They show high polarization with slight variations in the polarization degrees (∼1−3% at the brightness peak) with rapid declines with time (from ∼3−6% before the peak to ∼1% at ∼200 days after the peak). The general observational properties are consistent with the disk-CSM-interaction scenario, i.e., typical Type II SNe interacting with disk-like CSM. At the same time, the variation in the observational properties suggest diversity in the CSM mass and the opening angle of the CSM disk. These variations in the CSM properties are likely to be be related to the binary parameters of the progenitor systems and/or the properties of the progenitor and companion stars.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| 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".