The Tolman test for surface brightness (SB) dimming was originally proposed as a test for the expansion of the universe. The test, which is independent of the details of the assumed cosmology, is based on comparisons of the SB of identical objects at different cosmological distances. Claims have been made that the Tolman test provides compelling

Modern astronomic telescopes take advantage of multi-conjugate adaptive optics, in which wavefront sensors play a key role. A single sensor capable of measuring wavefront phases at any angle of observation would be helpful when improving atmospheric tomographic reconstruction. A new sensor combining both geometric and plenoptic arrangements is

We present the first release of the X-shooter Spectral Library (XSL). This release contains 237 stars. The spectra in this release span a wavelength range of 3000-10 200 Å and have been observed at a resolving power of R ≡ λ/ Δλ ~ 10 000. The spectra were obtained at ESO's 8-m Very Large Telescope (VLT). The sample contains O-M, long-period

We study the relationship between age, metallicity, and α-enhancement of FGK stars in the Galactic disk. The results are based upon the analysis of high-resolution UVES spectra from the Gaia-ESO large stellar survey. We explore the limitations of the observed dataset, i.e. the accuracy of stellar parameters and the selection effects that are caused

The Gaia-ESO Survey is a large public spectroscopic survey that aims to derive radial velocities and fundamental parameters of about 105 Milky Way stars in the field and in clusters. Observations are carried out with the multi-object optical spectrograph FLAMES, using simultaneously the medium-resolution (R ~ 20 000) GIRAFFE spectrograph and the

We present an analysis of the star formation history (SFH) of a field near the half-light radius in the Local Group dwarf irregular galaxy IC 1613 based on deep Hubble Space Telescope Advanced Camera for Surveys imaging. Our observations reach the oldest main sequence turn-off, allowing a time resolution at the oldest ages of ~1 Gyr. Our analysis