中国科学院云南天文台学术报告通知

2026年第4期

报告题目：Hot B Subdwarf Pulsators Observed with TESS and Asteroseismology of TIC 441725813

报告人：宿文超 博士

报告人单位：法国IRAP研究所/图卢兹大学

报告语言：中文

报告时间：2026年1月15日（星期四）10:30-12:00

报告地点：科研1号楼412会议室

报告摘要：

Hot subdwarf B (sdB) stars are compact, core-helium-burning stars that occupy a critical stage in stellar evolution. They play a pivotal role in understanding binary evolution, late stages of stellar evolution, and the formation of type Ia supernovae and gravitational wave sources. Despite their importance, the detailed formation channels and internal structures of sdB stars remain a subject of active research, with several open questions regarding their rotational properties, envelope compositions, and binary interactions.

We present a comprehensive study of sdB stars, with a particular focus on the hybrid pulsator TIC 441725813. As part of this work, we conducted a systematic survey of sdB candidates using photometric data from the Transiting Exoplanet Survey Satellite (TESS). Through rigorous selection and classification procedures, we identified a significant sample of targets that exhibit at least two out of three key features: g-mode pulsations, p-mode pulsations, and signs of binarity. This extensive catalog enriches the current understanding of the pulsation properties of sdB stars and provides an invaluable foundation for subsequent seismic modelling. For TIC 441725813, we performed an in-depth analysis of its TESS light curves, spanning over 670 days of continuous observations. The resulting frequency spectrum reveals a rich and complex pattern of g-mode and p-mode pulsations, along with clear signatures of rotational splitting and hints of binarity. From the observed splitting, we estimate the core rotation period to be approximately 85 days, with the envelope rotating about 4.7 times faster, suggesting differential rotation and possibly tidal interactions with a companion.

Building on the observed pulsation frequencies, we carried out detailed asteroseismic modelling of TIC 441725813 using fifth-generation (5G) forward models. The modelling was performed with a real-coded genetic algorithm that explored a 13-dimensional parameter space and evaluated nearly one million stellar models. The best-fit model successfully reproduces all 37 observed pulsation modes — including 35 g-modes and 2 p-modes — with a mean relative period deviation of only 0.14%. This marks the first seismic solution for a hybrid sdB pulsator that simultaneously fits both g- and p-mode frequencies at a comparable level of precision. The resulting stellar parameters are tightly constrained and fully consistent with independent estimates from spectroscopy and spectral energy distribution (SED) fitting. Internally, the star is characterized by a double-layered hydrogen/helium envelope and a relatively large convective core, with a helium mass fraction of 0.29 ± 0.05, and extending beyond the core boundary predicted by standard one-dimensional models. This provides observational evidence for significant convective core overshoot and efficient semi-convective mixing, in line with predictions from recent three-dimensional hydrodynamic simulations. 

报告人简介： 

Wenchao Su obtained his PhD from IRAP–CNRS / Université de Toulouse, following a master’s degree at Beijing Normal University. His research focuses on the asteroseismology of hot subdwarf stars and white dwarfs.

云台邀请方：恒星物理研究团组、国际超新星中心

邀请方联系人：吴涛