Please use this identifier to cite or link to this item: http://hdl.handle.net/10553/120268
Title: Measuring He i Stark Line Shapes in the Laboratory to Examine Differences in Photometric and Spectroscopic DB White Dwarf Masses
Authors: Schaeuble, Marc-Andre
Nagayama, T.
Bailey, J. E.
Gigosos, M. A.
Florido Hernández, Ricardo Jesús 
Blouin, Simon
Gomez, T. A.
Dunlap, Bart
Montgomery, Michael H.
Winget, Don E.
UNESCO Clasification: 230110 Espectroscopia de masas
220607-1 Espectroscopia láser
Issue Date: 2022
Journal: The Astrophysical journal 
Abstract: Accurate helium White Dwarf (DB) masses are crucial for understanding the DB masses derived using 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 He i Stark 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 He i Stark line-shape measurements at conditions relevant to DB atmospheres (T electron ≈12,000-17,000 K, n electron ≈ 1017 cm−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 He i Stark profiles only. Hβ, which has been well-studied in our platform and elsewhere, serves as the n e diagnostic. We find that He i Stark 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.
URI: http://hdl.handle.net/10553/120268
ISSN: 0004-637X
DOI: 10.3847/1538-4357/ac9df5
Source: Astrophysical Journal [ISSN 0004-637X], v. 940 (2), 181, (Diciembre 2022)
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