We report on the serendipitous discovery of a Herbig-Haro flow close to the pre-main sequence system HV Tauri. Low resolution spectra indicate a high excitation flow. The profile of emission lines seen at high resolution shows the existence of two velocity components, which are interpreted as emission from a bow shock directed towards the observer

β1 Monocerotis is a Be star with a V/R cycle of 12.5 years. We observed the star from CTIO (Chile) and with the IUE satellite and found that the star undergoes photospheric oscillations of 1.7 hours and presents a chromospheric structure in the extended atmosphere. Infall velocities and ejection of material are discussed.

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.