We present first results of an spectroscopic analysis of 7 O supergiants in Cyg OB2 using two different model atmosphere codes (Santolaya-Rey, Puls, Herrero, 1997, A&A 323, 488; and Hillier & Miller, 1998, ApJ 496, 407). The first code has been improved including an estimation of metal line blocking effects (Puls, in prep.). The second one has been

We present simultaneous and continuous observations of the Hα, Hβ, He I D3, Na I D1, D2 doublet and the Ca II H & K lines for the RS CVn system HR 1099. The spectroscopic observations were obtained during the MUSICOS 1998 campaign involving several observatories and instruments, both echelle and long-slit spectrographs. During this campaign, HR

Molecular lines are generally very good tracers of the physical conditions in cold regions of the Universe (e.g. molecular clouds, cool stars, etc.), but molecular species are also found in not so cold environments (e.g. the magnetized solar atmosphere). For a reliable interpretation of spectroscopic and spectropolarimetric observations of

We present spectropolarimetric observations of internetwork magnetic fields at the solar disk center. A Fabry-Pérot spectrometer was used to scan the two Fe I lines at 6301.5 and 6302.5 Å. High spatial resolution (0.5") magnetograms were obtained after speckle reconstruction. The patches with magnetic fields above noise cover approximately 45% of

Line profiles in ensuremath {{H}alpha } emission from H II region populations in spiral galaxies show emission features at +/-50 km/s from the main emission peaks of a significant fraction of regions, which are characteristic of expanding shells. We interpret these in two possible scenarios: mass-loaded wind outflows from the central OB stars, or