Asteroseismic analysis of the 'Methuselah' star (HD 140283)

The ’Methuselah’ star is one of the benchmark stars for the Gaia mission, thus knowing its properties very well is a high priority, and it has already been the subject of several studies, including a determination of its angular diameter (e.g., Karovicova et al. 2020). It is among the oldest known stars in the Galaxy and very metal-poor with a metallicity of [Fe/H] ∼ -2.4 dex (Bond et al. 2013), further stressing the importance of studying this star in detail. Fortuitously, it is also one of the brightest metal-poor halo stars (Creevey et al. 2015), opening up the possibility of conducting an asteroseismic analysis. However, this has not yet been achieved. We have obtained one sector of 20-second TESS data, and herein the oscillations in the ‘Methuselah’ star are apparent. In this contribution, I will present the outcome of our analysis, including a comparison with existing results. I will highlight what asteroseismology can bring to the table and emphasize that good external constraints are of paramount importance. Scrutinizing the ‘Methuselah’ star will not only advance our understanding of this particular star, but also of oscillations in very metal-poor stars in general. For example, oscillations have only been detected in very few stars of this low metallicity (e.g., HD 122563; Creevey et al. 2019), thus the 'Methuselah' star may represent the highest-𝜈_max metal-poor star for which detailed asteroseismic modeling, including mixed modes, is possible to date.