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arXiv · 2211.01868

Detection of cesium in the atmosphere of the hot He-rich white dwarf HD 149499B

P. Chayer·C. Mendoza·M. Meléndez·J. Deprince·J. Dupuis
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Abstract

We report the first detection of cesium (Z = 55) in the atmosphere of a white dwarf. Around a dozen absorption lines of Cs IV, Cs V, and Cs VI have been identified in the Far Ultraviolet Spectroscopic Explorer spectrum of the He-rich white dwarf HD 149499B (Teff = 49,500 K, log g = 7.97). The lines have equivalent widths ranging from 2.3 to 26.9 m\r{A}. We performed a spectral synthesis analysis to determine the cesium content in the atmosphere. Non-LTE atmosphere models were computed by considering cesium explicitly in the calculations. For this purpose we calculated oscillator strengths for the bound-bound transitions of Cs IV-Cs VI with both AUTOSTRUCTURE (multiconfiguration Breit-Pauli) and GRASP2K (multiconfiguration Dirac-Fock) atomic structure codes as neither measured nor theoretical values are reported in the literature. We determined a cesium abundance of log N(Cs)/N(He) = -5.45(0.35), which can also be expressed in terms of the mass fraction log X(Cs) = -3.95(0.35).

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P. Chayer, C. Mendoza, M. Meléndez, J. Deprince, J. Dupuis. 2022-11-03. Detection of cesium in the atmosphere of the hot He-rich white dwarf HD 149499B. https://doi.org/10.1093/mnras/stac3138

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