SN 1986J VLBI. The Evolution and Deceleration of the Complex Source and a Search for a Pulsar Nebula
Bibliographic record
Abstract
We report on VLBI observations of supernova 1986J in the spiral galaxy NGC 891 at two new epochs, 1990 July and 1999 February, t=7.4 and 15.9 yr after the explosion, and on a comprehensive analysis of these and earlier observations from t~4 yr after the explosion date, which we estimate to be 1983.2 +/- 1.1. The source is a shell or composite, and continues to show a complex morphology with large brightness modulations along the ridge and with protrusions. The supernova is moderately to strongly decelerated. The average outer radius expands as t^(0.71 +/- 0.11), and the expansion velocity has slowed to 6000 km/s at t=15.9 yr from an extrapolated 20,000 km/s at t=0.25 yr. The structure changes significantly with time, showing that the evolution is not self-similar. The shell structure is best visible at the latest epoch, when the protrusions have diminished somewhat in prominence and a new, compact component has appeared. The radio spectrum shows a clear inversion above 10 GHz. This might be related to a pulsar nebula becoming visible through the debris of the explosion. The radio flux density between 1.5 and 23 GHz decreases strongly with time, with the flux density proportional to t^(-2.94 +/- 0.24) between t~15 to 19 yr. This decrease is much more rapid than that found in earlier measurements up to t~6 yr.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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 | 0.001 |
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".