The bright supernova 1996cr in the circinus galaxy imaged with VLBI: shell structure with complex evolution
Bibliographic record
Abstract
ABSTRACT We present broad-band radio flux-density measurements supernova (SN) 1996cr, made with MeerKAT, ATCA, and ALMA, and images made from very long baseline interferometry (VLBI) observations with the Australian Long Baseline Array. The spectral energy distribution of SN 1996cr in 2020, at age t ∼8700 d, is a power-law, with flux density, S ∝ ν−0.588 ± 0.011 between 1 and 34 GHz, but may steepen at >35 GHz. The spectrum has flattened since t = 5370 d (2010). Also since t = 5370 d, the flux density has declined rapidly, with $S_{\rm 9 \, GHz} \propto t^{-2.9}$. The VLBI image at t = 8859 d shows an approximately circular structure with a central minimum reminiscent of an optically-thin spherical shell of emission. For a distance of 3.7 Mpc, the average outer radius of the radio emission at t = 8859 d was (5.1 ± 0.3) × 1017 cm, and SN 1996cr has been expanding with a velocity of 4650 ± 1060 km s−1 between t = 4307 and 8859 d. It must have undergone considerable deceleration before t = 4307 d. Deviations from a circular shell structure in the image suggest a range of velocities up to ∼7000 km s−1, and hint at the presence of a ring- or equatorial-belt-like structure rather than a complete spherical shell.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".