We have obtained I-band images for the new accreting millisecond pulsar XTE J1751-305 (IAUC#7867,#7870,#7872,#7874,#7876) with the 6.5-m Baade telescope and the MagIC CCD camera at the Las Campanas Observatory on 2002 April 14. At the position of the possible infrared counterpart (IAUC#7874), we found no optical sources to a limiting magnitude of I

We analyze very deep X-ray and mid-IR surveys in common areas of the Lockman Hole and the Hubble Deep Field-North (HDF-N) to study the sources of the X-ray background (XRB) and to test the standard obscured accretion paradigm. Observations with XMM-Newton and Infrared Space Observatory (ISO) of a substantial area in Lockman are particularly

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