Cepheid distances from the Baade-Wesselink method

TL;DR

This paper reviews recent advances in the Baade-Wesselink method, especially the infrared surface-brightness version, for accurately measuring Cepheid distances and discusses its implications for the Cepheid period-luminosity relation.

Contribution

It provides a detailed calibration of the IRSB Baade-Wesselink method, demonstrating its high accuracy and agreement with cluster-based distances, and compares it with other BW implementations.

Findings

IRSB method yields Cepheid distances accurate to 6%

Excellent agreement between IRSB and cluster Cepheid distances

Discussion on the universality of the Cepheid PL relation

Abstract

Recent progress on Baade-Wesselink (BW)-type techniques to determine the distances to classical Cepheids is reviewed. Particular emphasis is placed on the near-infrared surface-brightness (IRSB) version of the BW method. Its most recent calibration is described and shown to be capable of yielding individual Cepheid distances accurate to 6%, including systematic uncertainties. Cepheid distances from the IRSB method are compared to those determined from open cluster zero-age main-sequence fitting for Cepheids located in Galactic open clusters, yielding excellent agreement between the IRSB and cluster Cepheid distance scales. Results for the Cepheid period-luminosity (PL) relation in near-infrared and optical bands based on IRSB distances and the question of the universality of the Cepheid PL relation are discussed. Results from other implementations of the BW method are compared to the IRSB distance scale and possible reasons for discrepancies are identified.