Spectrum and Polarization of the Galactic Center Radio Transient ASKAP J173608.2–321635 from THOR-GC and VLITE
Bibliographic record
Abstract
Abstract The radio transient ASKAP J173608.2–321635, at the position (ℓ, b) = (356.°0872, −0.°0390), was serendipitously observed by The H i/OH/Recombination line survey of the Galactic center at three epochs in 2020 March, 2020 April, and 2021 February. The source was detected only on 2020 April 11 with a flux density of 20.6 ± 1.1 mJy at 1.23 GHz and in-band spectral index of α = −3.1 ± 0.2. The commensal Very Large Array Low-band Ionsophere and Transient Experiment simultaneously detected the source at 339 MHz with a flux density of 122.6 ± 20.4 mJy, indicating a spectral break below 1 GHz. The rotation measure (RM) in 2020 April was 63.9 ± 0.3 rad m−2, which almost triples the range of the variable RM observed by Wang et al. to ∼130 rad m−2. The polarization angle, corrected for Faraday rotation, was 97° ± 6°. The 1.23 GHz linear polarization was 76.7% ± 3.9% with wavelength-dependent depolarization, indicating a Faraday depth dispersion of σ ϕ = 4.8 − 0.7 + 0.5 rad m − 2 . We find an upper limit to the circular polarization of ∣V∣/I < 10.1%. Interpretation of the data in terms of diffractive scattering of radio waves by a plasma near the source indicates an electron density and a line-of-sight magnetic field strength within a factor of 3 of n e ∼ 2 cm−3 and B ∥ ∼ 2 × 105 μ G. Combined with causality limits to the size of the source, these parameters are consistent with the low-frequency spectral break resulting from synchrotron self-absorption, not free–free absorption. A possible interpretation of the source is a highly supersonic neutron star interacting with a changing environment.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".