On the He-3 anomaly in hot subdwarf B stars

Schneider D, Irrgang A, Heber U, Nieva MF, Przybilla N (2017)

Publication Status: Published

Publication Type: Conference contribution

Publication year: 2017

Publisher: SCIENDO

Book Volume: 26

Pages Range: 139-151

Journal Issue: 1

DOI: 10.1515/astro-2017-0430

Abstract

Decades ago, He-3 isotope enrichment in helium-weak B-type main-sequence, in blue horizontal branch and in hot subdwarf B (sdB) stars, i.e., helium-core burning stars of the extreme horizontal branch, were discovered. Diffusion processes in the atmosphere of these stars lead to the observed abundance anomalies. Quantitative spectral analyses of high-resolution spectra to derive photospheric isotopic helium abundance ratios for known He-3 sdBs have not been performed yet. We present preliminary results of high-resolution and high S/N spectra to determine the He-3 and He-4 abundances of nine known He-3 sdBs. We used a hybrid local/non-local thermodynamic equilibrium (LTE/NLTE) approach for B-type stars investigating multiple He I lines, including lambda 4922 angstrom and lambda 6678 angstrom, which show the strongest isotopic shifts in the optical spectral range. We also report the discovery of four new He-3 sdBs from the ESO Supernova Progenitor survey. Most of the He-3 sdBs cluster in a narrow temperature strip between similar to 26000 K and similar to 30000 K and have almost no atmospheric He-4 at all. Interestingly, three He-3 sdBs show evidence for vertical helium stratification.

Authors with CRIS profile

Involved external institutions

Leopold-Franzens-Universität Innsbruck / University of Innsbruck Austria (AT)

How to cite

APA:

Schneider, D., Irrgang, A., Heber, U., Nieva, M.F., & Przybilla, N. (2017). On the He-3 anomaly in hot subdwarf B stars. (pp. 139-151). SCIENDO.

MLA:

Schneider, David, et al. "On the He-3 anomaly in hot subdwarf B stars." SCIENDO, 2017. 139-151.

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