The Scale of Reddening for Classical Cepheid Variables

TL;DR

This paper compiles and compares various reddening measurements for 68 Cepheids, establishing a new standardized reddening scale with high precision, and investigates the intrinsic color dispersion related to pulsation periods.

Contribution

It introduces a new, highly precise reddening scale for Cepheids based on a comprehensive comparison of multiple methods and calibrations.

Findings

A new standardized reddening system with an average uncertainty of ±0.028 in E_B-V.

High-precision reddening measurements for 198 Cepheids.

Contradicts previous beliefs about the period dependence of temperature dispersion.

Abstract

Field reddenings are summarized for 68 Cepheids from published studies and updated results presented here. The compilation forms the basis for a comparison with other published reddening scales of Cepheids, including those established from reddening-independent indices, photometry on the Lick six-color system, Str\"{o}mgren system, Walraven system, Washington system, Cape $BVI$ system, DDO system, and Geneva system, IRSB studies, and Cepheid spectroscopy, both old and new. Reddenings tied to period-color relations are the least reliable, as expected, while photometric color excesses vary in precision, their accuracy depending on the methodology and calibration sample. The tests provide insights into the accuracy and precision of published Cepheid reddening scales, and lead to a new system of standardized reddenings comprising a sample of 198 variables with an average uncertainty of $\pm0.028$ in E$_{B-V}$, the precision being less than $\pm0.01$ for many. The collected color excesses are used to map the dispersion in intrinsic colors as a function of pulsation period, the results contradicting current perceptions about the period dependence of dispersion in Cepheid effective temperatures.