EVIDENCE FOR A MASSIVE NEUTRON STAR FROM A RADIAL-VELOCITY STUDY OF THE COMPANION TO THE BLACK-WIDOW PULSAR PSR B1957+20
Bibliographic record
Abstract
The most massive neutron stars constrain the behavior of ultra-dense matter, with larger masses possible only for increasingly stiff equations of state. Here, we present evidence that the black-widow pulsar, PSR B1957+20, has a high mass. We took spectra of its strongly irradiated companion and found an observed radial-velocity amplitude of <i>K</i><sub>obs</sub> = 324 ± 3 km s<sup>-1</sup>. Correcting this for the fact that, due to the irradiation, the center of light lies inward relative to the center of mass, we infer a true radial-velocity amplitude of <i>K</i><sub>2</sub> = 353 ± 4 km s<sup>-1</sup> and a mass ratio <i>q</i> = M<sub>PSR</sub>/M<sub>2</sub> = 69.2 ± 0.8. Combined with the inclination i = 65° ± 2° inferred from models of the light curve, our best-fit pulsar mass is M<sub>PSR</sub> = 2.40 ± 0.12 M<sub>☉</sub>. We discuss possible systematic uncertainties, in particular, in the light curve modeling. Taking an upper limit of <i>i</i> &lt; 85° based on the absence of radio eclipses at high frequency, combined with a conservative lower limit to the motion of the center of mass, <i>K</i><sub>2 </sub>&gt; 343 km s<sup>-1</sup> (<i>q </i>&gt; 67.3), we infer a lower limit to the pulsar mass of M<sub>PSR </sub>&gt; 1.66 M<sub>☉</sub>
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 teacher head, 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".