We study the behaviour of the interstellar R_n_=n(Zn^+^)/n(Na^0^) ratio in ionization equilibrium conditions. The ratio is very sensitive to variations of the physical state of the gas and is only marginally affected by variations of interstellar depletion. We find logR_n_ {in} [=~-2,=~0] dex in cold molecular clouds, logR_n_ {in} about [0,+1] dex

The vertical stellar distribution of the edge-on spiral NGC 6504 is examined in seven bands (U, B, R, I, J, H, K) by fitting model distributions to the light profile at seven positions along the major axis. In the inner parts of the disk the profile is well approximated by an exponential distribution. At large galactocentric distances, the profile

We present a direct determination of the mass of the system components in the soft X-ray transient A0620 -00. Infrared photometry during 1990 allows us to determine the double-humped quiescent light curve, which we then fit with an ellipsoidal model. We obtain solutions in the mass-ratio-inclination plane which, when combined with the rotational

I discuss in this paper the more likely physical mechanisms that could provide the energy input for the supersonic motions observed in giant extragalactic HII regions, together with preliminary results of an ongoing observational program that aims to study, with high spatial and spectral resolution, the kinematics of the ionized gas of the regions.

The kinematics of Planetary Nebulae are analyzed in terms of the solutions to the equations of hydrodynamic equilibrium developed by J. Canto. We apply our analysis to the Planetary Nebulae NGC 6905 and NGC 6537. A detailed spectroscopic study of these objects reveals the existence of high nuclear velocities, together with complex kinematic

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