Non-detection of 6Li in Spite plateau stars with ESPRESSO. Issue 1 (11th October 2021)

• Record Type: Journal Article
• Authors: Wang, Ella Xi; Nordlander, Thomas; Asplund, Martin; Lind, Karin; Zhou, Yixiao; Reggiani, Henrique
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 509:Issue 1(2022)
• Page Start: 1521
• Page End: 1535
• Publication Date: 2021-10-11
• Subjects: line: profiles -- radiative transfer -- techniques: spectroscopic -- stars: abundances -- stars: atmospheres -- stars: late-type; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab2924
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: The detection of 6 Li in Spite plateau stars contradicts the standard big bang nucleosynthesis prediction, known as the second cosmological lithium problem. We measure the isotopic ratio 6 Li/ 7 Li in three Spite plateau stars: HD 84937, HD 140283, and LP 815−43. We use 3D non-local thermodynamic equilibrium radiative transfer and for the first time apply this to high-resolution, high signal-to-noise ratio data from the ultra-stable ESPRESSO/Very Large Telescope spectrograph. These are among the best spectra ever taken of any metal-poor stars. As the measurement of 6 Li/ 7 Li is degenerate with other physical stellar parameters, we employ Markov chain Monte Carlo methods to find the probability distributions of measured parameters. As a test of systematics, we also use three different fitting methods. We do not detect 6 Li in any of the three stars, and find consistent results between our different methods. We estimate 2σ upper limits to 6 Li/ 7 Li of 0.7, 0.6, and 1.7 per cent, respectively, for HD 84937, HD 140283, and LP 815−43. Our results indicate that there is no second cosmological lithium problem, as there is no evidence of 6 Li in Spite plateau stars.