A precise asteroseismic age and metallicity for HD 139614: a pre-main-sequence star with a protoplanetary disc in Upper-Centaurus Lupus

TL;DR

This study uses asteroseismology to precisely determine the age and metallicity of the pre-main-sequence star HD 139614, providing new insights into its properties and the early stages of planet formation.

Contribution

It presents the first asteroseismic measurement of metallicity for a λ Boo star and confirms the star's pre-main-sequence status with precise age and composition.

Findings

Age of 10.75 ± 0.77 Myr for HD 139614

Mass of 1.52 ± 0.02 solar masses

Global metallicity Z = 0.0100 ± 0.0010

Abstract

HD\,139614 is known to be a $\sim$14-Myr-old, possibly pre-main-sequence star in the Sco-Cen OB association in the Upper Centaurus-Lupus subgroup, with a slightly warped circumstellar disc containing ring structures hinting at one or more planets. The star's chemical abundance pattern is metal-deficient except for volatile elements, which places it in the $\lambda$ Boo class and suggests it has recently accreted gas-rich but dust-poor material. We identify seven dipole and four radial pulsation modes among its $\delta$ Sct pulsations using the TESS light curve and an \'echelle diagram. Precision modelling with the MESA stellar evolution and GYRE stellar oscillation programs confirms it is on the pre-main sequence. Asteroseismic, grid-based modelling suggests an age of $10.75\pm0.77$ Myr, a mass of $1.52\pm0.02$ M$_{\odot}$, and a global metal abundance of $Z=0.0100\pm0.0010$. This represents the first asteroseismic determination of the bulk metallicity of a $\lambda$ Boo star. The precise age and metallicity offer a benchmark for age estimates in Upper Centaurus--Lupus, and for understanding disc retention and planet formation around intermediate-mass stars.