We present a detailed analysis of 101 white dwarf main-sequence binaries (WDMS) from the Sloan Digital Sky Survey (SDSS) for which multiple SDSS spectra are available. We detect significant radial velocity variations in 18 WDMS, identifying them as post-common-envelope binaries (PCEBs) or strong PCEB candidates. Strict upper limits to the orbital

With high angular resolution, high temporal cadence and a stable point spread function, the Solar Optical Telescope (SOT) onboard the Hinode satellite is the ideal instrument for the study of magnetic flux emergence and its manifestations on the solar surface. In this presentation, we focus on the development of ephemeral regions and small active

We present a review on the determination of the primordial helium abundance, Y_p, based on the study of hydrogen and helium recombination lines in extragalactic H II regions. We also discuss the observational determinations of the increase of helium to the increase of oxygen by mass Δ Y/Δ O , and compare them with predictions based on models of

We present the project Local Cosmology from Isolated Dwarfs (LCID), aimed at deriving detailed star-formation histories for a sample of Local Group isolated dwarf galaxies. To accomplish this goal we have collected, using the ACS on board the HST, color-magnitude diagrams reaching the oldest main sequence turnoff (V ≃ 29) with good photometric

Available from the Minor Planet Center.

Aims:The aim of this paper is to analyze the thermal properties, oscillatory, and flow motions of a bright, long-lasting feature observed in solar granulation, which we call the plume. Methods: We used the spectral observations of quiet granulation at solar disc center, including the two Fe II 5234 and Fe I 6393 Å lines recorded simultaneously at