A precise asteroseismic age and metallicity for HD139614: a pre-main-sequence star with a protoplanetary disc in Upper Centaurus-Lupus

HD139614 is known to be a similar to 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 +/- 0.77Myr, a mass of 1.52 +/- 0.02M(circle dot), and a global metal abundance of Z = 0.0100 +/- 0.0010. 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.

Automated summary

HD139614 is a possibly pre-main-sequence star in the Sco-Cen OB association with a slightly warped circumstellar disc containing ring structures hinting at one or more planets. The star's chemical abundance pattern and pulsation modes have been studied to determine its nature and provide insights into its properties.