SAX J1810.8−2609: an outbursting neutron star X-ray binary with persistent spatially coincident radio emission
Bibliographic record
Abstract
ABSTRACT Here, we report on joint X-ray and radio monitoring of the neutron star low-mass X-ray binary SAX J1810.8−2609. Our monitoring covered the entirety of its ${\sim }\, 5\,$ month outburst in 2021, revealing a temporal correlation between its radio and X-ray luminosity and X-ray spectral properties consistent with a ‘hard-only’ outburst. During the outburst, the best-fitting radio position shows significant variability, suggesting emission from multiple locations on the sky. Furthermore, our 2023 follow-up observations revealed a persistent, unresolved, steep spectrum radio source ${\sim }\, 2\,$ yr after SAX J1810.8−2609 returned to X-ray quiescence. We investigated potential origins of the persistent emission, which included an unrelated background source, long-lasting jet ejection(s), and SAX J1810 as a transitional millisecond pulsar. While the chance coincidence probability is low (${\lesssim }\, 0.16~{{\ \rm per\ cent}}$), an unrelated background source remains the most likely scenario. SAX J1810.8−2609 goes into outburst every ${\sim }\, 5\,$ yr, so monitoring of the source during its next outburst at higher sensitivities and improved spatial resolutions (e.g. with the Karl G. Jansky Very Large Array or Square Kilometre Array) should be able to identify two components (if the persistent emission originates from a background source). If only one source is observed, this would be strong evidence that the persistent emission is local SAX J1810.8−2609, and future monitoring campaigns should focus on understanding the underlying physical mechanisms, as no neutron star X-ray binary has shown a persistent radio signal absent any simultaneous X-ray emission.
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".