中国科学院云南天文台学术报告通知

2025年第46期

报告题目：Volume-limited sample of low-mass red giant stars,the progenitors of hot subdwarf stars

报告人：Diego Benitez

报告人单位：Universidad de Valparaíso

报告语言：English

报告时间：2025年8月22日（星期五）14:30-15:30

报告地点：科研1号楼412会议室

报告摘要：

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Hot subdwarf B (sdB) stars are core-helium-burning objects with typical masses near the core-helium-flash mass and a very thin hydrogen-rich envelopes, which challenge standard single-star evolutionary models. Thanks to many observational campaigns and theoretical efforts, their formation is now generally understood to involve close-binary interactions: stable Roche lobe overflow (RLOF) produces long-period sdB binaries, common-envelope (CE) evolution leads to short-period sdB binaries, and double white dwarf mergers result in single sdBs. However, several important details, such as stability criteria for mass loss, the detailed physics of the CE phase, accretion efficiency onto companions, and mass-loss fractions during stable RLOF, remain poorly understood. To address these open questions, we are conducting a dedicated spectroscopic survey aiming to identify a statistically significant, homogeneous sample of possible progenitors of long-period sdBs, which are predicted to be low-mass first giant branch (FGB) stars with F, G, or K-type main-sequence companions. By combining Gaia DR3 parallaxes with astrometric quality criteria, we selected a volume-limited sample of candidate pre-RLOF RGB binaries within 500 pc. These stars are being followed with high-resolution spectroscopy to obtain very precise radial velocities (RVs) and derive the distribution of their stellar parameters. Our goal is to determine the binary fraction within the sample and constrain orbital solutions by monitoring RV variations. Once established, the final progenitor sample, together with the existing 500 pc volume-limited sdB sample, will be incorporated as priors in binary population synthesis models, significantly improving theoretical constraints.

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报告人简介： 

Diego Benitez graduated with a bachelor’s degree in Physics from the Universidad Nacional de Asunción,Paraguay,in 2021. In 2022,he joined the Universidad de Valparaíso as a Master’s student and completed the program in 2024. He began his PhD studies at the Universidad de Valparaíso under the supervision of Prof. Maja Vuckovic in this year, working with the binary star research group. His main research field is the observational spectroscopy of sdB stars and their progenitors, specifically low- to intermediate-mass FGB stars in binary systems. He has gained experience using several mid- and high-resolution optical spectrographs in Chile, as well as in reducing and analyzing spectroscopic data.

云台邀请方：大样本恒星演化研究团组、国际超新星中心、云南省国际超新星研究重点实验室

邀请方联系人：李谢瑾