Chandra Observations of the Newly Discovered Magnetar Swift J1818.0–1607
Bibliographic record
Abstract
Abstract Swift J1818.0–1607 is a new radio-loud magnetar discovered by the Swift Burst Alert Telescope on 2020 March 12. It has a magnetic field B ∼ 2.5 × 1014 G, spin-down luminosity ∼ 7.2 × 1035 erg s−1, and characteristic age τ c ∼ 470 yr. Here we report on the Chandra observations of Swift J1818.0–1607, which allowed for a high-resolution imaging and spectroscopic study of the magnetar and its environment. The 1–10 keV spectrum of the magnetar is best described by a single blackbody model with a temperature of 1.2 ± 0.1 keV and an unabsorbed flux of 1.9−0.3 +0.4 × 10−11 erg cm−2 s−1. This implies an X-ray luminosity of 9.6−1.5 +2.0×1034 d 6.5 2 erg s−1 and efficiency of ∼ 0.13 d 6.5 2 at a distance of 6.5 kpc. The Chandra image also shows faint diffuse emission out to from the magnetar, with its spectrum adequately described by a power law with a photon index of 2.0 ± 0.5 and a luminosity of ∼8.1 × 1033 erg s−1. The extended emission is likely dominated by a dust-scattering halo and future observations of the source in quiescence will reveal any underlying compact wind nebula. We conclude that Swift J1818.0–1607 is a transient source showing properties between high-B pulsars and magnetars, and could be powered at least partly by its high spin-down, similar to rotation-powered pulsars.
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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 | 0.000 |
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".