Shell helium-burning hot subdwarf B stars as candidates for blue large-amplitude pulsators

Abstract

Blue large-amplitude pulsators (BLAPs) are a newly discovered type of variable star. Their typical pulsation periods are on the order of a few tens of minutes, with relatively large amplitudes of 0.2-0.4 mag in optical bands, and their rates of period changes are on the order of $10^{-7}y{r}^{-1}$ (both positive and negative). They are extremely rare objects and attempts to explain their origins and internal structures have attracted a great deal of attention. Previous studies have proposed that BLAPs may be pre-white dwarfs, with masses around $0.3M_{\odot }$, or core-helium-burning stars in the range of $\sim 0.7-1.1M_{\odot }$. In this work, we use a number of MESA models to compute and explore whether BLAPs could be explained as shell helium-burning subdwarfs type B (SHeB sdBs). The models that best match existing observational constraints have helium core masses in the range of $\sim 0.45-0.5M_{\odot }$. Our model predicts that the positive rate of period change may evolve to negative. The formation channels for SHeB sdBs involve binary evolution and although the vast majority of BLAPs do not appear to be binaries (with the exception of HD 133729), the observational constraints are still very poor. Motivated by these findings, we explored the Roche lobe overflow channel. Of the 304 binary evolution models we computed, about half of them are able to produce SHeB sdBs in long-period binaries that evade detection from the limited observations that are currently available.

A&A accepted

References in corpus (21)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• Hot subdwarf binaries from the MUCHFUSS project - Analysis of 12 new systems and a study of the short-period binary population
• Mass transfer from a giant star to a main sequence companion and its contribution to long-orbital-period blue stragglers
• Adiabatic mass loss in binary stars. III. From the base of the red giant branch to the tip of asymptotic giant branch
• Blue large-amplitude pulsators as a new class of variable stars
• Discovery of post-mass-transfer helium-burning red giants using asteroseismology
• A new class of pulsating hot subdwarfs
• Subdwarf B stars from the common envelope ejection channel
• Evolution models of helium white dwarf--main sequence star merger remnants
• Evolutionary modelling of subdwarf B stars using MESA with the predictive mixing and convective premixing schemes
• Pulsation in faint blue stars
• Radial velocity variability and evolution of hot subdwarf stars
• Hydrogen in hot subdwarfs formed by double helium white dwarf mergers
• Binary evolution pathways of Blue Large-Amplitude Pulsators
• The masses of hot subdwarfs
• HD 133729: A blue large-amplitude pulsator in orbit around a main-sequence B-type star
• Identifying Blue Large Amplitude Pulsators from Gaia DR2 & ZTF DR3
• An 18.9-minute Blue Large-Amplitude Pulsator Crossing the 'Hertzsprung Gap' of Hot Subdwarfs
• Hot subdwarf B stars with neutron star components II: Binary population synthesis
• Confirmation of Monoperiodicity Above 20 Seconds for Two Blue Large-Amplitude Pulsators

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• Binary Evolution Pathways to Blue Large-Amplitude Pulsators: Insights from HD 133729
• The oscillation properties of the Blue Large Amplitude Pulsators (BLAPs): relative change rate of periods, excitations, and period relations
• A Minute-Cadence Deep Bulge Survey: First Data Release of DREAMS