The eccentric millisecond pulsar, PSR J0955−6150
Bibliographic record
Abstract
Context.PSR J0955−6150 is a member of an enigmatic class of eccentric millisecond pulsar (MSP) and helium white dwarf (He WD) systems (eMSPs), whose binary evolution is poorly understood and believed to be strikingly different to that of traditional MSP+He WD systems in circular orbits. Aims.Measuring the masses of the stars in this system is important for testing the different hypotheses for the formation of eMSPs. Methods.We carried out timing observations of this pulsar with the Parkes radio telescope using the 20 cm multibeam and ultra-wide bandwidth low-frequency (UWL) receivers, and theL-band receiver of the MeerKAT radio telescope. The pulse profiles were flux and polarisation calibrated, and a rotating-vector model (RVM) was fitted to the position angle of the linear polarisation of the combined MeerKAT data. Pulse times of arrival (ToAs) were obtained from these using standard pulsar analysis techniques and analysed using theTEMPO2 timing software. Results.Our observations reveal a strong frequency evolution of this MSP’s intensity, with a flux density spectral index (α) of −3.13(2). The improved sensitivity of MeerKAT resulted in a greater than tenfold improvement in the timing precision obtained compared to our older Parkes observations. This, combined with the eight-year timing baseline, has allowed precise measurements of a very small proper motion and three orbital post-Keplerian parameters, namely the rate of advance of periastron,ω̇ = 0.00152(1) deg yr−1, and the orthometric Shapiro delay parameters,h3 = 0.89(7) μs and ς = 0.88(2). Assuming general relativity, we obtainMp = 1.71(2) M⊙for the mass of the pulsar andMc = 0.254(2) M⊙for the mass of the companion; the orbital inclination is 83.2(4) degrees. Crucially, assuming that the position angle of the linear polarisation follows the RVM, we find that the spin axis has a misalignment relative to the orbital angular momentum of > 4.8deg at 99% confidence level. Conclusions.While the value ofMpfalls well within the wide range observed in eMSPs,Mcis significantly smaller than expected from several formation hypotheses proposed, which are therefore unlikely to be correct and can be ruled out;Mcis also significantly different from the expected value for an ideal low mass X-ray binary evolution scenario. If the misalignment between the spin axis of the pulsar and the orbital angular momentum is to be believed, it suggests that the unknown process that created the orbital eccentricity of the binary was also capable of changing its orbital orientation, an important evidence for understanding the origin of eMSPs.
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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 | 0.001 |
| 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".