A new method is developed to calculate the amplitude of the galactic warps generated by a torque due to external forces. This takes into account that the warp is produced as a reorientation of the different rings which constitute the disc in order to compensate the differential precession generated by the external force, yielding a uniform

We present two dimensional kinematic observations at high angular and velocity resolution measured via the Hα emission line in the active barred spiral NGC 6951, obtained using the TAURUS II Fabry-Perot system on the 4.2 m William Herschel Telescope. From the radial velocity map we produced the rotation curve, which has a rapidly rising inner

An analysis of Hα and Hβ spectra in a sample of 30 cool dwarf and subgiant stars is presented using MARCS model atmospheres based on the most recent calculations of the line opacities. A detailed quantitative comparison of the solar flux spectra with model spectra shows that Balmer line profile shapes, and therefore the temperature structure in the

The European Space Agency (ESA) has undertaken the development of Optical Data Relay payloads, aimed at establishing free space optical communication links between satellites. The first of such systems put into orbit is the SILEX project, in which an experimental link between a GEO satellite (ARTEMIS) and a LEO satellite (SPOT IV) will be used to

We present high resolution spectroscopic data of the two giant extragalactic H II regions NGC 5461 and NGC 5471 in M101, which have been obtained with the 2.1-m telescope of the Observatorio Astronómico Nacional in San Pedro Martir, Baja California. We measured the intensities of several H and He recombination lines, and of forbidden lines of a

Its combination of good spatial resolution and soft X-ray sensitivity make Chandra an ideal instrument for the detection of luminous supersoft X-ray sources (SSSs)in external galaxies. M31 may provide the best opportunity to study a galactic population of SSSs. We have recently completed a survey of ~ 2560 square arcmin ( ~ 131 kpc^2) of M31