Hard X-Ray Observation and Multiwavelength Study of the PeVatron Candidate Pulsar Wind Nebula “Dragonfly”
Bibliographic record
Abstract
Abstract We studied the PeVatron nature of the pulsar wind nebula (PWN) G75.2+0.1 (“Dragonfly”) as part of our NuSTAR observational campaign of energetic PWNe. The Dragonfly is spatially coincident with LHAASO J2018+3651, whose maximum photon energy is 0.27 PeV. We detected a compact (radius 1 ′ ) inner nebula of the Dragonfly without a spectral break in 3–20 keV using NuSTAR. A joint analysis of the inner nebula with archival Chandra and XMM-Newton (XMM) observations yields a power-law spectrum with Γ = 1.49 ± 0.03. Synchrotron burnoff is observed from the shrinkage of the NuSTAR nebula at higher energies, from which we infer the magnetic field in the inner nebula of 24 μG at 3.5 kpc. Our analysis of archival XMM data and 13 yr of Fermi-LAT data confirms the detection of an extended ( ∼ 10 ′ ) outer nebula in 2–6 keV (Γ = 1.82 ± 0.03) and the nondetection of a GeV nebula, respectively. Using the VLA, XMM, and HAWC data, we modeled a multiwavelength spectral energy distribution of the Dragonfly as a leptonic PeVatron. The maximum injected particle energy of 1.4 PeV from our model suggests that the Dragonfly is likely a PeVatron. Our model prediction of the low magnetic field (2.7 μG) in the outer nebula and recent interaction with the host supernova remnant’s reverse shock (4 kyr ago) align with common features of PeVatron PWNe. The origin of its highly asymmetric morphology, pulsar proper motion, PWN–supernova remnant (SNR) interaction, and source distance will require further investigations in the future, including a multiwavelength study using radio, X-ray, and gamma-ray observations.
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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 | 0.001 | 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".