A precise asteroseismic age and metallicity for HD 139614: a pre-main-sequence star with a protoplanetary disc in Upper Centaurus–Lupus. Issue 2 (20th January 2021)

• Record Type: Journal Article
• Authors: Murphy, Simon J; Joyce, Meridith; Bedding, Timothy R; White, Timothy R; Kama, Mihkel
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 502:Issue 2(2021)
• Page Start: 1633
• Page End: 1646
• Publication Date: 2021-01-20
• Subjects: asteroseismology -- protoplanetary discs -- stars: chemically peculiar -- stars: fundamental parameters -- stars: pre-main-sequence -- variables: Scuti; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab144
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: HD 139614 is known to be a ∼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 λ 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 δ Sct pulsations using the TESS light curve and an échelle 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 ± 0.77 Myr, a mass of 1.52 ± 0.02 M ⊙, and a global metal abundance of Z = 0.0100 ± 0.0010. This represents the first asteroseismic determination of the bulk metallicity of a λ 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.