Metal-poor Type II Cepheids with Periods Less Than Three Days
Metal-poor Type II Cepheids with Periods Less Than Three Days
We have analyzed 10 high-resolution spectra of Type II Cepheids with periods less than 3 days. We find that they clearly separate into two groups: those with near or slightly below solar metallicities, and those with [Fe/H] between −1.5 and −2.0. While the former are usually called BL Her stars, …