SUPERNOVA 1986J VERY LONG BASELINE INTERFEROMETRY. II. THE EVOLUTION OF THE SHELL AND THE CENTRAL SOURCE
Bibliographic record
Abstract
We present new Very Long Baseline Interferometry (VLBI) images of supernova (SN) 1986J, taken at 5, 8.4, and 22 GHz between t = 22 and 25 yr after the explosion. The shell expands ∝ t 0.69±0.03 . We estimate the progenitor's mass-loss rate at (4–10) × 10 −5 M ☉ yr −1 (for v w = 10 km s −1 ). Two bright spots are seen in the images. The first, in the northeast, is now fading. The second, very near the center of the projected shell and unique to SN 1986J, is still brightening relative to the shell, and now dominates the VLBI images. It is marginally resolved at 22 GHz (diameter ∼0.3 mas; ∼5 × 10 16 cm at 10 Mpc). The integrated VLA spectrum of SN 1986J shows an inversion point and a high-frequency turnover, both progressing downward in frequency and due to the central bright spot. The optically thin spectral index of the central bright spot is indistinguishable from that of the shell. The small proper motion of 1500 ± 1500 km s −1 of the central bright spot is consistent with our previous interpretation of it as being associated with the expected black-hole or neutron-star remnant. Now, an alternate scenario seems also plausible, where the central bright spot, like the northeast one, results when the shock front impacts on a condensation within the circumstellar medium (CSM). The condensation would have to be so dense as to be opaque at cm wavelengths (∼10 3 × denser than the average corresponding CSM) and fortuitously close to the center of the projected shell. We include a movie of the evolution of SN 1986J at 5 GHz from t = 0 to 25 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 | 0.000 |
| 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 | 0.000 | 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".