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Abstract Accurate helium White Dwarf (DB) masses are critical for understanding the star’s evolution. DB masses derived from the spectroscopic and photometric methods are inconsistent. Photometric masses agree better with currently accepted DB evolutionary theories and are mostly consistent across a large range of surface temperatures. Spectroscopic masses rely on untested HeiStark line-shape and Van der Waals broadening predictions, show unexpected surface temperature trends, and are thus viewed as less reliable. To test this conclusion, we present in this paper detailed HeiStark line-shape measurements at conditions relevant to DB atmospheres (Telectron≈12,000–17,000 K,nelectron≈ 1017cm−3). We use X-rays from Sandia National Laboratories’Z-machine to create a uniform ≈120 mm long hydrogen–helium mixture plasma. Van der Waals broadening is negligible at our experimental conditions, allowing us to measure HeiStark profiles only. Hβ, which has been well-studied in our platform and elsewhere, serves as thenediagnostic. We find that HeiStark broadening models used in DB analyses are accurate within errors at tested conditions. It therefore seems unlikely that line-shape models are solely responsible for the observed spectroscopic mass trends. Our results should motivate the WD community to further scrutinize the validity of other spectroscopic and photometric input parameters, like atmospheric structure assumptions and convection corrections. These parameters can significantly change the derived DB mass. Identifying potential weaknesses in any input parameters could further our understanding of DBs, help elucidate their evolutionary origins, and strengthen confidence in both spectroscopic and photometric masses.
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This content will become publicly available on August 1, 2026
BEAST X for Bayesian phylogenetic, phylogeographic and phylodynamic inference
Abstract Here we present the open-source and cross-platform BEAST X software that combines molecular phylogenetic reconstruction with complex trait evolution, divergence-time dating and coalescent demographics in an efficient statistical inference engine.BEAST Xsignificantly advances the flexibility and scalability of evolutionary models supported. Novel clock and substitution models leverage a large variety of evolutionary processes; discrete, continuous and mixed traits with missingness and measurement errors; and fast, gradient-informed integration techniques that rapidly traverse high-dimensional parameter spaces.
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- PAR ID:
- 10638958
- Publisher / Repository:
- Nature
- Date Published:
- Journal Name:
- Nature Methods
- Volume:
- 22
- Issue:
- 8
- ISSN:
- 1548-7091
- Page Range / eLocation ID:
- 1653 to 1656
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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