The net circular polarization observed in solar faculae (Stenflo et al., 1984) follows a law expected from the combination of velocity and magnetic field gradients in the photosphere. To show this, the theoretical curve of growth (net circular polarization produced by a single line versus its absorption coefficient) predicted by this mechanism is

In this paper, we investigate the eclipse timing of the polar binary HU Aquarii that has been observed for almost two decades. Recently, Qian et al. attributed large (O-C) deviations between the eclipse ephemeris and observations to a compact system of two massive Jovian companions. We improve the Keplerian, kinematic model of the light travel time

We present an optical spectrum (λλ4000-10 500) of the lensed blazar B0218+357 secured at the 10 m GTC and aimed to investigate and clarify the properties of this intriguing system. We found that the emission line spectrum of the blazar is characterized by only one broad emission line that interpreted as Mg ii 2800 Å yields z = 0.95. In addition, we

We present a detailed multiwavelength study (from rest-frame ultraviolet to far-infrared) of narrow-band selected, star-forming (SF) Hα emitters (HAEs) at z ˜ 2.23 taken from the High-Redshift(Z) Emission Line Survey (HiZELS). We find that HAEs have similar properties and colours derived from spectral energy distributions as sBzK galaxies, and

We carried out Chandra observations of two low-luminosity low-mass X-ray binaries, 1RXS J170854.4-321857 and 1RXS J171824.2-402934, for which previously single X-ray bursts were detected with the Wide Field Cameras (WFCs) on board BeppoSAX. Both were detected in our Chandra observations in an actively accreting state three to eight years after the

We investigate the relation between the radio (Fr) and optical (Fo) flux densities of a variety of classes of radio transients and variables, with the aim of analysing whether this information can be used, in the future, to classify such events. Using flux density values between 1 and 10 GHz and the optical bands V and R, we build a sample with a