Dwarf satellite galaxies undergo strong tidal forces produced by the main galaxy potential. These forces disturb the satellite and produce asymmetries in its stellar distribution, tidal tail formation, and modifications of the velocity dispersion profiles. Most of these features are observed in the Ursa Minor (UMi) dwarf spheroidal galaxy, which is

Recently, a new class of type I X-ray bursters was suggested, the ``burst-only sources'', i.e. detected only during an X-ray burst, and no persistent emission around the burst. Short follow-up observations of several burst-only sources could not unambiguously identify the X-ray burster, but suggested that they were at luminosities comparable to

The Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) is an imaging system and a low-resolution long-slit and multi-object spectrograph for the 10.4m Spaninsh telescope GTC. OSIRIS spectral range (from 365 up to 1000 nm) and observing modes require a wide set of elements in order to provide imaging and spectroscopic

A catalog of optical warps of galaxies is presented. This can be considered complementary to that reported by Sanchez-Saavedra et al. (1990MNRAS.246..458S), with 42 galaxies in the northern hemisphere, and to that by Reshetnikov & Combes (1999A&AS..138..101R), with 60 optical warps. The limits of the present catalog are: logr25>0.60, B1

We present observations of a Mg X 625 Å coronal line, obtained with the CDS instrument on SoHO, extending from the disk part of the coronal hole to ~ 90 000 km above the limb in the north polar coronal hole. Observations were performed in polar plumes and inter-plume lanes. To obtain a sufficiently high signal-to-noise ratio the observations were

Tight stability requirements for the imager/spectrograph OSIRIS (a Day One optical instrument for the GTC telescope) demand a careful treatment of thermal effects within the OSIRIS camera. Mostly due to the thermal response of refraction indices of its glasses (and not so much to curvature, spacing or thickness variations of the lenses), the camera