We have observed seven main sequence stars in the Pleiades, with B - V between 0.98 and 1.41 (5100-3900 K), and with a wide range of rotational velocities, in Ca II H and K, Ha and have derived Li abundances. Our results, combined with literature data, indicate that the most chromospherically active stars are rapid rotators, and that at a given

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A spectrophotometric study of the peculiar open cluster Berkeley 87 is presented; the measurements show that most of the members are young, heavily reddened OB stars, but a few are much more evolved objects. Some of these objects show in their spectra the presence of unusual absorption lines, probably due to the local interstellar medium. The stars

SIMURIS is an interferometric investigation of the very fine structure of the solar atmosphere from the photosphere to the corona. It was proposed to ESA /1/, November 30 1989, for the Next Medium Size Mission - M2, and accepted in February 1990 for an Assessment Study in the context of the Space Station. The main scientific objectives will be

We explore the use of the flux difference between the lines Fe 15250 Å and Fe 15247 Å as a technique to measure photospheric magnetic fields in late-type stars. The technique developed takes into account all the LTE physics of the problem, assuming a radial and homogeneous magnetic field distribution over the stellar surface. Some test calculations