The Hipparcos mission has made it possible to constrain the positions of nearby field stars in the colour-magnitude diagram with very high accuracy. These positions can be compared with the predictions of stellar evolutionary calculations to provide information on the basic parameters of the stars: masses, radii, effective temperatures, ages, and

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The optical transient of the faint gamma-ray burst GRB 990308 was detected by the QUEST camera on the Venezuelan 1 m Schmidt telescope starting 3.28 hr after the burst. Our photometry gives V=18.32+/-0.07, R=18.14+/-0.06, B=18.65+/-0.23, and R=18.22+/-0.05 for times ranging from 3.28 to 3.47 hr after the burst. The colors correspond to a spectral

We derive a bound on the magnetic dipole moment of the top quark in the context of the effective Lagrangian approach by using the ratios Rb=Γb/Γh, Rl=Γh/Γl and the Z width. We take into account the vertex and oblique corrections. We obtain the allowed region for the magnetic dipole moment of top quark as -2.94

This thesis presents observational kinematic results for a significant sample of disk galaxies. Spectra of both the gaseous and stellar components are available for almost the whole sample. The first aim was to make a comparative study of the gas and the stellar kinematics to see whether there was any correlation between the kinematic behavior and

IAUC 7273 available at Central Bureau for Astronomical Telegrams.