Observations of PSR J2021+3651 and its X‐Ray Pulsar Wind Nebula G75.2+0.1
Bibliographic record
Abstract
We present the results from X-ray and radio observations of the recently discovered young Vela-like pulsar PSR J2021+3651, which is coincident with the EGRET γ-ray source GeV 2020+3658. A 19.0 ks Chandra ACIS-S observation has revealed a ~20'' × 10'' pulsar wind nebula that is reminiscent of the equatorial tori seen around some young pulsars, along with thermal emission from an embedded point source ( kT ∞ = 0.15 ± 0.02 keV). We have named the nebula G75.2+0.1. Its spectrum is well fitted by an absorbed power-law model with a photon index of Γ = 1.7 , a hydrogen column density of N H = (7.8 ) × 10 21 cm -2 , and an unabsorbed 0.5-10.0 keV flux of (1.7 ± 0.1) × 10 -12 ergs cm -2 s -1 . We have spatially fitted G75.2+0.1 with a model that assumes a toroidal morphology, and from this we infer that the axis of the torus is highly inclined to the line of sight. A 20.8 ks Chandra observation in continuous-clocking mode reveals a possible pulse detection, with a pulsed fraction of ~65% and an H -test probability of occurring by chance of 8.9 × 10 -5 . Timing observations with the Arecibo radio telescope spanning 2 yr show that PSR J2021+3651 glitched sometime between MJD 52,616 and 52,645 with parameters Δν/ν = (2.587 ± 0.002) × 10 -6 and Δ / = (6.2 ± 0.3) × 10 -3 , similar to those of the largest glitches observed in the Vela pulsar. PSR J2021+3651 is heavily scattered (τ sc = 17.7 ± 0.9 ms at 1 GHz) and exhibits a significant amount of timing noise.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| 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) | 0.000 | 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 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".