Xiran Xie | Searcharxiv

arXiv2026

Precise parameter determination of the open cluster NGC 1647 via asteroseismology of p-mode pulsators

Asteroseismology of member pulsators provides a robust physical constraint on cluster parameters by linking internal stellar structures to the global properties of the host cluster. However, the parameters of NGC 1647 remains poorly constrained due to limited investigation, a situation that cluster asteroseismology can significantly refine. In this study, we identified 271 high confidential cluster members in NGC 1647, using HDBSCAN clustering with radial-velocity validation. Its initial age is determined in the range of 1250-280 Myr, derived from isochrone fitting based on multi-survey metallicities extinction-corrected Gaia photometry. Among the members, we found 96 periodic variables from TESS and K2 photometry, including nine p-mode pulsators (five δ Sct and four hybrid δ Sct-γ Dor stars). Assuming a common cluster age and initial chemical composition, joint asteroseismic modeling is performed based on measured large frequency separations and individual mode frequencies. This yields a metallicity of [Fe/H] = -0.08+0.04-0.01, well consistent with the spectroscopic determinations, and a seismic age of 178+11-9 Myr, more precise than isochrone-based estimates. This work shows the diagnostic potential of δ Sct asteroseismology in young open clusters and establishes a high-precision benchmark for future studies of NGC 1647 and other open clusters.

astro-ph.SR↗

arXiv2025

Precise Asteroseismology of the High-amplitude Delta Scuti Star EH Librae, an AE UMa Analogue in the Hertzsprung Gap

A subclass of intermediate mass variables Delta Scuti stars, known as High-amplitude Delta Scuti (HADS) stars, exhibits pronounced radial pulsations with high amplitudes. The ground-based and space-based observations of the HADS star EH Lib are used to help making asteroseismological analysis of this pulsating star. Following the reduction of the light curves, the frequency analysis reveals the fundamental frequency as $f_0=11.3105$ c day$^{-1}$ and two more significant frequencies $f_1$ and $f_2$, in addition to the harmonics of $f_0$ and a linear combination. The period change rate is determined as $(1/P_0)(dP_0/dt)=(5.4\pm0.5)\times10^{-9}$ yr$^{-1}$ derived from an O-C diagram, which is constructed from 342 times of maximum light spanning over 70 years. Using these observational constraints, along with the metallicity reported in the literature, we construct theoretical models using the stellar evolution code MESA and calculate the theoretical frequencies of the eigen modes using the oscillation code GYRE. The appropriate models are selected by matching both $f_0$ and $(1/P_0)(dP_0/dt)$ within their respective uncertainties. The results indicate that the observed period change of EH Lib can be attributed to stellar evolutionary effects. The stellar parameters of EH Lib are derived as: the mass of $1.715\pm0.065$ M$_{\odot}$, the luminosity of log $(L/L_{\odot})=1.38\pm0.06$, and the age of $(1.14\pm0.13)\times10^{9}$ years. EH Lib is classified as a single-mode HADS star, locating currently in the Hertzsprung gap, with a helium core and a hydrogen-burning shell. This work expands the asteroseismological sample of HADS stars and establishes a foundation for future investigations into their commonalities and specific properties, thereby advancing our understanding of these variables.

astro-ph.SR↗