The Reacceleration of the Shock Wave in the Radio Remnant of SN 1987A
Bibliographic record
Abstract
Abstract We report on updated radio imaging observations of the radio remnant of SN 1987A at 9 GHz, taken with the Australia Telescope Compact Array (ATCA), covering a 25 yr period (1992–2017). We use Fourier modeling of the supernova remnant to model its morphology, using both a torus model and a ring model, and find that both models show an increasing flux density and have shown a continuing expansion of the remnant. As found in previous studies, we find that the torus model most accurately fits our data and has shown a change in the remnant expansion at day 9300 ± 210 from 2300 ± 200 km s−1 to 3610 ± 240 km s−1. We have also seen an increase in brightness in the western lobe of the remnant, although the eastern lobe is still the dominant source of emission, unlike what has been observed at contemporary optical and X-ray wavelengths. We expect to observe a reversal in this asymmetry by the year ∼2020, and we note that the southeastern side of the remnant is now beginning to fade, as has also been seen in optical and X-ray data. Our data indicate that high-latitude emission has been present in the remnant from the earliest stages of the shock wave interacting with the equatorial ring around day 5000. However, we find that the emission has become increasingly dominated by the low-lying regions by day 9300, overlapping with the regions of X-ray emission. We conclude that the shock wave is now leaving the equatorial ring, exiting first from the southeast region of the remnant, and is reaccelerating as it begins to interact with the circumstellar medium beyond the dense inner ring.
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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".