Binary evolution pathways to blue large-amplitude pulsators: Insights from HD 133729

¹ Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011, PR China
² University of the Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, PR China
³ International Centre of Supernovae, Yunnan Key Laboratory, Kunming 650216, PR China
⁴ Institute for Frontier in Astronomy and Astrophysics, Beijing Normal University Beijing 102206, PR China
⁵ Department of Astronomy, Beijing Normal University, Beijing 100875, PR China

^⋆ Corresponding authors: wuchengyuan@ynao.ac.cn; wangbo@ynao.ac.cn

Received: 14 January 2025
Accepted: 14 April 2025

Abstract

Blue large-amplitude pulsators (BLAPs) are a recently identified class of pulsating stars distinguished by their short pulsation periods (2–60 minutes) and asymmetric light curves. This study investigated the evolutionary channel of HD 133729, which is the first confirmed BLAP in a binary system. Using the binary evolution code MESA, we explored various mass ratios and initial orbital periods. Our simulations suggest that a system with a mass ratio q = 0.30 undergoing non-conservative mass transfer (β = 0.15) can reproduce the observed characteristics through the pre-white-dwarf Roche lobe overflow channel. Meanwhile, we postulate that there are significant helium and nitrogen enhancements on the surface of the main sequence (MS) star. The system will eventually undergo the common envelope phase, leading to a stellar merger. HD 133729 is a unique case, providing crucial insights into the formation mechanism and evolutionary fate of BLAPs with MS companions. This work constrains the elemental abundances of the MS star and has advanced our understanding of non-conservative mass transfer in binary evolution.