Latest Results from XL-Calibur - A Balloon Borne Hard X-Ray Polarimetry Mission
Bibliographic record
Abstract
The linear polarisation of hard X-ray emission from the Crab pulsar/wind nebula and black-hole binary Cygnus X-1 has been measured by XL-Calibur. Observations took place in July 2024 during a week-long stratospheric balloon flight between northern Sweden and Canada. The addition of polarimetry to the standard high-energy measurement techniques of spectroscopy, timing and imaging, allows systematically new tests of source emission and geometry models. XL-Calibur incorporates an X-ray mirror, which focusses X-rays onto a polarimeter comprising a beryllium rod surrounded by Cadmium Zinc Telluride detectors. The polarimeter is housed in a thick$\text{Bi}_{4} \text{Ge}_{3} \mathrm{O}_{12}$anticoincidence shield to mitigate measurement backgrounds. The mirror and polarimeter-shield assembly are mounted at opposite ends of a 12 m long lightweight truss, which is pointed with WASP - the Wallops Arc Second Pointer. XL-Calibur is the most sensitive hard X-ray polarimetry mission to date, offering an order-of-magnitude improvement in signal-to-background performance compared to preceding missions. The energy range ($15-80 \text{keV}$) complements the NASA/ASI IXPE mission ($2-8 \text{keV}$), allowing broadband studies. I will describe the XL-Calibur mission, and summarise latest results from observations. Plans for future flights of XL-Caliburwill also be discussed.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.003 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.006 |
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".