On The Impact Of 22Ne On The Pulsation Periods Of Carbon-Oxygen White Dwarfs With Helium Dominated Atmospheres

• Published in: arXiv.org
• Main Authors: Chidester, Morgan T, Timmes, F X, Schwab, Josiah, Townsend, Richard H D, Farag, Ebraheem, Thoul, Anne, Fields, C E, Bauer, Evan B, Montgomery, Michael H
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 20.01.2021
• Subjects: Astronomical models; Carbon; Dipoles; Helium; Physics - Solar and Stellar Astrophysics; Pulsation; Quadrupoles; Stellar evolution; White dwarf stars
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2101.08352

We explore changes in the adiabatic low-order g-mode pulsation periods of 0.526, 0.560, and 0.729 M\(_\odot\) carbon-oxygen white dwarf models with helium-dominated envelopes due to the presence, absence, and enhancement of \(^{22}\)Ne in the interior. The observed g-mode pulsation periods of such white dwarfs are typically given to 6\(-\)7 significant figures of precision. Usually white dwarf models without \(^{22}\)Ne are fit to the observed periods and other properties. The root-mean-square residuals to the \(\simeq\) 150\(-\)400 s low-order g-mode periods are typically in the range of \(\sigma_{rms}\) \(\lesssim\) 0.3 s, for a fit precision of \(\sigma_{rms}/ P\) \(\lesssim\) 0.3 %. We find average relative period shifts of \(\Delta P/P\) \(\simeq\) \(\pm\) 0.5 % for the low-order dipole and quadrupole g-mode pulsations within the observed effective temperature window, with the range of \(\Delta P/P\) depending on the specific g-mode, abundance of \(^{22}\)Ne, effective temperature, and mass of the white dwarf model. This finding suggests a systematic offset may be present in the fitting process of specific white dwarfs when \(^{22}\)Ne is absent. As part of the fitting processes involves adjusting the composition profiles of a white dwarf model, our study on the impact of \(^{22}\)Ne can provide new inferences on the derived interior mass fraction profiles. We encourage routinely including \(^{22}\)Ne mass fraction profiles, informed by stellar evolution models, to future generations of white dwarf model fitting processes.