Asteroseismology of 35 Kepler and TESS $\delta$ Scuti stars near the red edge of the instability strip. The limitations of $\delta$ Scuti stars for dating open clusters

Abstract

Aims. The aim of this work is to determine the maximum ages that can be unambiguously established for $\delta$ Sct stars using seismic observables, and, by extension, the oldest open clusters that can be dated using this type of star. Methods. I estimate the large frequency separation using various techniques applied to two samples of $\delta$ Sct located near the red edge of the instability strip. One sample consists of 18 targets observed by the Kepler mission, and the other comprises 17 targets observed by TESS. I employ a grid of stellar models representative of typical $\delta$ Sct parameters, incorporating mass, metallicity, and rotation as independent variables, and compute the first eight radial modes for each model. Using the observed spectroscopic temperature, and the estimated large separation, I estimate the age of each star by fitting a weighted probability density function to the age distribution of the models that best match the seismic constraints. Results. To evaluate the performance of the fitting method, it was applied to a synthetic population of 20 $\delta$ Sct stars with varying metallicities and ages, generated by randomly selecting models. The analysis indicates that $\delta$ Sct stars older than 1 Gyr, but still prior to reaching the terminal-age main sequence, can in principle be reliably age-dated. Nevertheless, when the method is applied to the observational sample, only three out of the 35 stars considered marginally exceed an estimated age of 1 Gyr. Conclusions. From these results, I can say that open clusters older than approximately 1 Gyr cannot be reliably dated using astero-seismology of $\delta$ Sct stars with 1D models, at least not without a more complete treatment of convection and a non-linear treatment of rotation.

arXiv comment11 pages, 7 figures. Supplementary figures in Zenodo: https://doi.org/10.5281/zenodo.17067341

References in corpus (25)

• Kepler Mission Design, Realized Photometric Performance, and Early Science
• GYRE: An open-source stellar oscillation code based on a new Magnus Multiple Shooting Scheme
• APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South
• The Kepler characterization of the variability among A- and F-type stars. I. General overview
• Rotational velocities of A-type stars. III. Velocity distributions
• Hybrid gamma Doradus - delta Scuti pulsators: New insights into the physics of the oscillations from Kepler observations
• {\em Gaia}-derived luminosities of {\em Kepler} A/F stars and the pulsator fraction across the δ Scuti instability strip
• Activity indicators and stellar parameters of the Kepler targets. An application of the ROTFIT pipeline to LAMOST-Kepler stellar spectra
• Spectroscopic survey of Kepler stars. I. HERMES/Mercator observations of A- and F-type stars
• Very regular high-frequency pulsation modes in young intermediate-mass stars
• Interaction Between Convection and Pulsation
• High frequency A-type pulsators discovered using SuperWASP
• Observational $\Delta \nu$-$\bar{\rho }$ relation for $\delta$ Sct stars using eclipsing binaries and space photometry
• Turbulent Convection and pulsational Stability of Variable Stars I. Oscillations of Long-Period Variables
• An in-depth study of HD 174966 with CoRoT photometry and HARPS spectroscopy. Large separation as a new observable for δSct stars
• Precise surface gravities of $\delta$ Scuti stars from asteroseismology
• TESS observations of the Pleiades cluster: a nursery for delta Scuti stars
• A new method for the inversion of atmospheric parameters of A/Am stars
• Models of rotating massive stars: impacts of various prescriptions
• A study of correlation between the oscillation amplitude and stellar parameters for delta Scuti stars in open clusters. Toward selection rules for delta Scuti stars oscillations
• A Large Sample of Am Candidates from LAMOST Data Release 1
• FILOU oscillation code
• Unexpected series of regular frequency spacing of delta Scuti stars in the non-asymptotic regime -- I. The methodology
• Determining the seismic age of the young open cluster $\alpha$ Per using $\delta$ Scuti stars
• Dating young open clusters using delta Scuti stars. Results for Trumpler 10 and Praesepe