| A multiwavelength analysis of BL Her stars: Models vs Observations |
| Susmita Das |
| Konkoly Observatory, CSFK, Hungary |
| We present new theoretical period-luminosity (PL), period-Wesenheit (PW) amd period-radius (PR)relations at multiple wavelengths (Johnson-Cousin-Glass bands UBVRIJHKLL'M and Gaia passbands G G_BP G_RP) for a fine grid of convective BL Herculis models computed using the non-linear radial stellar pulsation tool MESA-RSP. The non-linear models were computed for periods typical for BL Her stars, i.e. 1≤P (days)≤4 covering a wide range of input parameters: metallicity (-2.0 dex≤ [Fe/H]≤ 0.0 dex), stellar mass (0.5M⊙ -0.8M⊙ ), luminosity (50L⊙ -300L⊙ ) and effective temperature (full extent of the instability strip; in steps of 50K). We investigate the impact of four sets of different convection parameters on the multi-wavelength properties. Most empirical relations match well with the theoretical PL, PW and PR relations from the BL Her models computed using the four sets of convection parameters. However, PL slopes of the models with radiative cooling provide a better match to empirical relations for BL Her stars in the LMC in the G-band and the HK_S bands. No significant metallicity effects are seen in the PR relations. Another important result from our grid of BL Her models is that it supports the equivalence of the PL relations of RR Lyrae and T2Cs, thereby providing us the opportunity of adopting RRLs + T2Cs together as an alternative to classical Cepheids for the extragalactic distance scale calibration. |