Speaker
Description
Cepheid variables serve as fundamental standard candles for calibrating the extragalactic distance scale. The high-precision parallaxes from Gaia now enable a sub-percent calibration of the Period-Luminosity (PL) relation for Milky Way (MW) Cepheids. However, interstellar extinction remains the main source of uncertainty, as the Cepheids’ variability complicates direct reddening measurements.
We present a novel approach to estimate extinction by leveraging non-variable field stars in the neighborhood of Cepheids. Using medium-high-resolution VLT/FLAMES spectroscopic observations, we determine the stellar parameters (Teff, log g, [M/H]) of these stars. Combining these parameters with multi-band photometry (e.g., Gaia, 2MASS) and atmospheric models, we derive their individual extinction, A(V). This results in a high-resolution 3D extinction map, from which we interpolate the Cepheid reddening.
By refining extinction corrections, we will enhance the calibration of the MW Cepheid PL relation, thereby contributing to more precise distance measurements.