Multiwavelengthp observations of a GRB detected by INTEGRAL (GRB 030227) revealed a dim optical afterglow (OA) that would not have been detected by many previous searches due to its faintess (R~ 23). This OA was seen to decline following a power law decay with index α = -0.95 +/- 0.16. The spectral index β of the OA yields -1.32 +/- 0.15, with the

The GREGOR Fabry-Pérot Interferometer (GFPI) is one of three first-light instruments of the German 1.5-meter GREGOR solar telescope at the Observatorio del Teide, Tenerife, Spain. The GFPI allows fast narrow-band imaging and post-factum image restoration. The retrieved physical parameters will be a fundamental building block for understanding the

One of the most promising explanations for the origin of the billion solar mass black holes (BHs) inferred to power quasars at redshifts z >= 6 is that supermassive stars (SMSs) with masses >=104Msolar collapse to form the seed BHs from which they grow. Here we review recent theoretical advances which provide support for this scenario. Firstly

Context. Transiting planets offer an excellent opportunity for characterizing the atmospheres of extrasolar planets under very different conditions from those found in our solar system. Aims: We are currently carrying out a ground-based survey to obtain the transmission spectra of several extrasolar planets using the 10 m Gran Telescopio Canarias

We present 20 yr of radial velocity (RV) measurements of the M1 dwarf Gl15A, combining five years of intensive RV monitoring with the HARPS-N spectrograph with 15 yr of archival HIRES/Keck RV data. We have carried out an MCMC-based analysis of the RV time series, inclusive of Gaussian Process (GP) approach to the description of stellar activity

We present some theoretical predictions concerning the amplitude and magnetic sensitivity of the linear-polarization signals produced by scattering processes in the hydrogen Lyα line of the solar transition region. To this end, we have calculated the atomic-level polarization (population imbalances and quantum coherences) induced by anisotropic