Mode Switching in Two Blue Large-amplitude Pulsators Observed by OGLE, KMTNet, and DREAMS

Abstract Blue large-amplitude pulsators (BLAPs) are rare, hot, short-period pulsating stars whose rapid oscillations provide a unique probe of stellar interiors and atmospheres. In this paper, we study two short-period BLAPs in the Galactic bulge, Optical Gravitational Lensing Experiment (OGLE)-BLAP-142 ( P ≈ 6.6 minutes) and OGLE-BLAP-148 ( P ≈ 7.5 minutes), by combining light curves from the OGLE, KMTNet, and DREAMS surveys, spanning 17 yr with cadences ranging from minutes to hours to days. We perform generalized Lomb–Scargle periodogram analyses of their light curves and identify, for each BLAP, three closely spaced pulsation modes separated by ∼1%. The dominant mode can switch within timescales of order a year, accompanied by a likely blueward color shift (∼0.1–0.2 mag). The yearly period excursions of the resolved mode families imply apparent ∣ P ̇ / P ∣ values of order 10 −6 –10 −4 yr −1 , large enough to mimic or exceed smooth evolutionary period changes. One mode family in OGLE-BLAP-148 shows a coherent decade-long drift at the ∼10 −5 yr −1 level, but its failure to extrapolate to the earliest and latest epochs suggests a transient mode-family drift rather than secular evolution. Such close-spaced multiple pulsations and mode switching may be common among BLAPs with periods shorter than 10 minutes, and their physical origin remains unclear.

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Publication Details

Journal
The Astrophysical Journal
Published
2026-11-02
DOI
https://doi.org/10.3847/1538-4357/aea902
Primary Topic
Stellar, planetary, and galactic studies
Type
article
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0.00

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article

Mode Switching in Two Blue Large-amplitude Pulsators Observed by OGLE, KMTNet, and DREAMS

Weicheng Zang, Shude Mao, Steve R. Heathcote, Chung‐Uk Lee et al.
3 links
The Astrophysical Journal
Stellar, planetary, and galactic studies
article

Mode Switching in Two Blue Large-amplitude Pulsators Observed by OGLE, KMTNet, and DREAMS

Weicheng Zang, Shude Mao, Steve R. Heathcote, Chung‐Uk Lee, Qiyue Qian, Przemek Mróz, A. Zenteno, Tomás Ahumada, Yaosong Yu, Guillermo Damke, Zhixing Li, Yuxin Shang, Hongjing Yang, Yuchen Tang, Konstantina Boutsia, Dong-Jin Kim, Timothy Abbott, Tianjun Gan, Andong Xu, Tao Wu, Zhenhao Wang, Seung-Lee Kim, Hao Ma
article en

Abstract

Abstract Blue large-amplitude pulsators (BLAPs) are rare, hot, short-period pulsating stars whose rapid oscillations provide a unique probe of stellar interiors and atmospheres. In this paper, we study two short-period BLAPs in the Galactic bulge, Optical Gravitational Lensing Experiment (OGLE)-BLAP-142 ( P ≈ 6.6 minutes) and OGLE-BLAP-148 ( P ≈ 7.5 minutes), by combining light curves from the OGLE, KMTNet, and DREAMS surveys, spanning 17 yr with cadences ranging from minutes to hours to days. We perform generalized Lomb–Scargle periodogram analyses of their light curves and identify, for each BLAP, three closely spaced pulsation modes separated by ∼1%. The dominant mode can switch within timescales of order a year, accompanied by a likely blueward color shift (∼0.1–0.2 mag). The yearly period excursions of the resolved mode families imply apparent ∣ P ̇ / P ∣ values of order 10 −6 –10 −4 yr −1 , large enough to mimic or exceed smooth evolutionary period changes. One mode family in OGLE-BLAP-148 shows a coherent decade-long drift at the ∼10 −5 yr −1 level, but its failure to extrapolate to the earliest and latest epochs suggests a transient mode-family drift rather than secular evolution. Such close-spaced multiple pulsations and mode switching may be common among BLAPs with periods shorter than 10 minutes, and their physical origin remains unclear.

The Astrophysical JournalVol. 1011(2)
Universidad de La Laguna (ES), Chinese Academy of Sciences (CN), Korea Astronomy and Space Science Institute (KR), Westlake University (CN), Instituto de Astrofísica de Canarias (ES), Cerro Tololo Inter-American Observatory (CL), NSF NOIRLab (US), University of Chinese Academy of Sciences (CN), University of Warsaw (PL), Tsinghua University (CN)
Westlake University, National Natural Science Foundation of China, Chinese Academy of Sciences, China Postdoctoral Science Foundation, Korea Astronomy and Space Science Institute, Narodowym Centrum Nauki, Korea Research Environment Open Network
Openalex Percentile: Top 30%
Stellar, planetary, and galactic studies
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