Speaker
Description
We present theoretical period-luminosity (PL), period-Wesenheit (PW), and period-radius (PR) relations for BL Herculis stars (the shortest period Type II Cepheids), with a focus on their application to the Rubin-LSST survey. Using non-linear convective MESA-RSP models spanning periods of 1–4 days, metallicities (–2.0 ≤ [Fe/H] ≤ 0.0 dex), masses of 0.5–0.8 M⊙, and the full instability strip, we investigate their multi-wavelength pulsation properties. We find no significant metallicity dependence in the PL relations, supporting a universal PL relation for BL Her stars. To assess the connection between the models and forthcoming time-domain observations, we employ a robust light-curve optimization method to identify best-fitting model-observed pairs for BL Her stars in the Large Magellanic Cloud using the Gaia bands. We also provide the first theoretical predictions in the Rubin-LSST passbands, laying the groundwork for using Type II Cepheids as distance indicators in the Rubin era.