New Theoretical Instability Regions, Period–Luminosity Relations, and Masses for Blue Large-amplitude Pulsators

Abstract Blue large-amplitude pulsators (BLAPs) are a recently discovered group of hot pulsating stars whose evolutionary status remains uncertain. Their proposed progenitors are either ≃0.3 M ⊙ shell H-burning stars or ≃1.0 M ⊙ core He-burning stars, both relying on mass loss or a merger event in a (rarely observed) close interacting binary system. With the goal of understanding the stellar masses of BLAPs, we therefore carried out a linear nonadiabatic analysis of a grid of models computed using mesa-rsp , with appropriate input stellar parameters ZXMLT eff and convection parameter sets. We discuss the impact of stellar mass, metallicity, helium abundance, and convection parameters on the theoretical instability regions of BLAPs. We also derive new theoretical period relations; those based on low stellar masses show better agreement with the observed period relations. Although only two BLAPs have been observed to be multiperiodic oscillators so far, we analyse theoretical P 1O / P F ratios and compare these values with other classical pulsators. Furthermore, we provide the first asteroseismic mass estimate for the triple-mode pulsator OGLE-BLAP-030, which seems to be well constrained in the range of 0.62–0.64 M ⊙ with a high metallicity of Z = 0.07, albeit with a few sources of uncertainty involved. This would place the BLAP star intermediate to the two proposed mass scenarios so far.