Context. The second Gaia data release (Gaia DR2) provides precise five-parameter
astrometric data (positions, proper motions, and parallaxes) for an unprecedented number of …

In the era of precision cosmology, it is essential to determine the Hubble constant empirically
with an accuracy of one per cent or better. At present, the uncertainty on this constant is …

Context. RR Lyrae stars are excellent tracers of the oldest stars (ages≳ 9–10 Gyr) and
standard candles for measuring the distance to stellar systems that are mainly composed of …

Previous studies based on the analysis of Gaia DR2 data have revealed that accreted stars,
possibly originating from a single progenitor satellite, are a significant component of the halo …

Context. The Gaia second Data Release (DR2) presents a first map** of full-sky RR Lyrae
stars and Cepheids observed by the spacecraft during the initial 22 months of science …

Estimates of the Hubble constant, H 0, from the local distance ladder and from the cosmic
microwave background (CMB) are discrepant at the∼ 3σ level, indicating a potential issue …

We present results from the analysis of 401 RR Lyrae stars (RRLs) belonging to the field of
the Milky Way (MW). For a fraction of them multiband (V, K s, W 1) photometry, metal …

We have compiled the first all-sky mid-infrared variable-star catalog based on Wide-field
Infrared Survey Explorer five-year survey data. Requiring more than 100 detections for a …

Context. Classical Cepheids are the most important primary indicators for the extragalactic
distance scale. Establishing the precise zero points of their period-luminosity and period …

Aims. Classical Cepheids provide the foundation for the empirical extragalactic distance
ladder. Milky Way Cepheids are the only stars in this class accessible to trigonometric …