The conditions of the exosphere of Mercury constitute a prime example of a magnetosphere subject to space weather. We aim at improving the diagnostic of the physical conditions of Na atoms in the exosphere of Mercury, with particular emphasis in the possibility of inferring the magnetic field through polarimetry of the Na D emission lines. We

We present spectra obtained with the 10.4 m Gran Telescopio Canarias telescope of 13 Galactic H II regions, most of them of very low ionization degree. The objects are located along the Galactic disc, with RG from 5.7 to 16.1 kpc. We determine Te([N II]) for all of them. We obtain - for the first time - a radial abundance gradient of N that is

Optical photometry of HIDEEP galaxies was carried out using a combination of SExtractor (Bertins & Arnouts, 1996A&AS..117..393B) and the STSDAS package in IRAF, where the ellipse task was used to obtain radial surface brightness profiles. (2 data files).

Aims: We aim to monitor the optical linear polarimetric signal of the magnetized, rapidly rotating M8.5 dwarf TVLM 513-46546. Methods: R- and I-band linear polarimetry images were collected with the Andalucía Faint Object Spectrograph and Camera (ALFOSC) instrument of the 2.56-m Nordic Optical Telescope (NOT) on two consecutive nights, covering

Optical imaging of RX J105453.3+552102 was carried out at the 2.5m NOT telescope in March 2008. Optical deep images were used for studying the properties of the brightest group galaxy and for computing the photometric luminosity function of the group. We have also performed a detail dynamical analysis of the system based on redshift data for 116

We report the identification of RXJ0636 as a new intermediate polar. The system's light curves and spectral analysis, together with a variety of its physical parameters are presented. A brief description of the observations leading to the above mentioned identification is also given.