Cepheid Abundances: Multiphase Results and Spatial Gradients

Abstract

Parameters and abundances have been derived for 435 Cepheids based on an analysis of 1127 spectra. Results from five or more phases are available for 52 of the program stars. The latter set of stars span periods between 1.5 and 68 days. The parameters and abundances show excellent consistency across phase. For iron, the average range in the determined abundance is 0.11 from these 52 stars. For 163 stars with more than one phase available the average range is 0.07. The variation in effective temperature tracks well with phase, as does the total broadening velocity. The gravity and microturbulent velocity follow phase, but with less variation and regularity. Abundance gradients have been derived using GAIA DR2 parallax data (GAIA Collaboration et al. 2016, 2018), as well as Bayesian distance estimates based upon GAIA DR2 from Bailer-Jones et al. (2018). The abundance gradient derived for iron is d[Fe/H]/dR = -0.05 dex/kpc, similar to gradients derived in previous studies.