Constraining the age of HD 140283

Sammanfattning: HD 140283, also known as the Methuselah star, is an old, metal-poor star on the subgiant branch.It has been the subject of many studies due to its relatively large apparent brightness, and due to itbeing one of the oldest stars known. Accurate age measurements can therefore put limits on the ageof the Universe, and help constrain cosmological models. We present a new investigation of the ageof HD 140283, based on the precise parallax measured by Gaia, PARSEC and BaSTI stellar isochronemodels, and a careful consideration of systematics. We find τ = 13.8 ± 0.5 Gyr, where the error isdominated by the effective temperature uncertainty. This does not imply an obvious tension with thestandard ΛCDM cosmological model (τuniverse = 13.80 ± 0.02 Gyr).