Discovery of Outlying High‐Velocity Oxygen‐Rich Ejecta in Cassiopeia A
Bibliographic record
Abstract
Analysis of broadband HST ACS and WFPC2 images of the young Galactic supernova remnant Cassiopeia A reveals a far larger population of outlying, high-velocity knots of ejecta with a broader range of chemical properties than previously suspected. In this paper, we concentrate on a ≃ 1.5 arcmin2 region located along the eastern limb of the remnant where we identify three main classes of outer ejecta: (1) knots dominated by [N II] λλ6548, 6583 emission, (2) knots dominated by oxygen emission lines, especially [O II] λλ7319, 7330, and (3) knots with emission-line strengths similar to the [S II]-strong fast-moving knot (FMK) ejecta commonly seen in the main emission shell. Mean transverse velocities derived from observed proper motion for N-rich, O-rich, and FMK-like knots identified in this region were found to be 8100, 7900, and 7600 km s-1, respectively. The discovery of a significant population of O-rich ejecta situated between the suspected N-rich outer photospheric layer and S-rich FMK-like ejecta suggests that the progenitor's chemical layers were not completely disrupted by the supernova explosion outside of the remnant's northeast and southwest high-velocity "jet" regions. In addition, we find the majority of O-rich outer ejecta at projected locations out beyond the remnant's fastest moving Fe-rich X-ray emission material seen in Chandra and XMM-Newton data along the eastern limb, suggesting that penetration of Fe-rich material up through the S- and Si-rich mantle did not extend past the progenitor's N- or O-rich outer layers for this section of the remnant.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".