We derive a first-order linear differential equation describing the shape of the probability density function (PDF) of magnetic field strengths in the quiet Sun. The modeling is very schematic. It considers convective motions which continuously supply and withdraw magnetic structures. In addition, a magnetic amplification mechanism increases the

We present preliminary results of our high-resolution (R≥50000) spectroscopic survey of line-profile variations in stars with spectral types similar to β Cephei stars. In this paper we focus on the observations obtained on La Palma with the William Herschel Telescope (WHT) and with the Nordic Optical Telescope (NOT), to complement both the Southern

Phase-resolved high-resolution optical spectroscopy has revealed narrow NIII and HeII emission lines from the soft X-ray transient Aquila X-1 during its 2004 outburst that move as a function of the orbit consistent with the phasing of the donor star. Under the assumption that these lines come from the irradiated side of the donor star, we can

We present a detailed investigation of the young stellar populations (YSP) in the radio-loud ultraluminous infrared galaxy (ULIRG), PKS1345+12 (z = 0.12), based on high-resolution Hubble Space Telescope (HST) imaging and long-slit spectra taken with the William Herschel Telescope (WHT) at La Palma. While the images clearly show bright knots

Aims:We introduce analytical response functions and their main properties as an important diagnostic tool that help understand Stokes profile formation physics and the meaning of well-known behaviors of standard inversion codes of the radiative transfer equation often used to measure solar magnetic fields. Methods: A Milne-Eddington model

We report on the discovery of a faint (MV~-10.6+/-0.2) dwarf spheroidal galaxy on deep F606W and F814W Hubble Space Telescope images of a Virgo intracluster field. The galaxy is easily resolved in our images, as our color magnitude diagram (CMD) extends >~1 magnitude beyond the tip of the red giant branch (RGB). Thus, it is the deepest CMD for a