The Leavitt law of Milky Way Cepheids from Gaia DR2 static companion parallaxes

Understand

Classical Cepheids (CCs) are at the heart of the empirical extragalactic distance ladder.

• Milky Way CCs are the only stars of this class accessible to trigonometric parallax measurements.
• Until recently, the most accurate trigonometric parallaxes of Milky Way CCs were the HST/FGS measurements collected by Benedict et al.
• (2002, 2007) and HST/WFC3 measurements by Riess et al.