The faint extended broad (>=1000 km s-1) optical emission lines associated with giant H II regions are shown here to be produced in a shell of ISM material smoothly accelerated soon after breakout. Two-dimensional calculations of remnants caused by a strong energy deposit in a low metal abundance ISM are here shown to undergo breakout once

We present the initial results of a study aimed at: (1) determining the lifetime of the disk accretion phase among low mass pre-main sequence stars; (2) establishing the time dependence of disk mass accretion rates; and (3) further exploring the role played by accretion disks in regulating stellar rotation. Our laboratory for this study is NGC 2264

Very young late-type dwarfs at distances closer than 30 pc are excellent sites to provide a direct detection of extrasolar planets. The combination of youth and proximity makes feasible the detection of giant planets of 1-5 Jovian masses orbiting at several astronomical units from the star. According to current models, giant planets with masses 1

In an effort to test stellar structure and evolution models, analysis of oscillations in A and F stars in open clusters is carried out by the STACC network (Frandsen cite{stacc}). In this paper we describe our effort to locate a suitable open cluster in the northern hemisphere for a future multi-site campaign. We present BV Johnson and time series

We present an analysis of the optical spectroscopy of 58 stars in the Galactic plane at l=27^° , where a prominent excess in the flux distribution and star counts have been observed in several spectral regions, in particular in the Two-Micron Galactic Survey (TMGS) catalog. The sources were selected from the TMGS to have a K magnitude brighter than

An analysis of a ROSAT/PSPC observation of the galaxy cluster A2634 is presented. The cluster has a luminosity of 7.9+/-0.1x10^43^erg/s in the ROSAT band (0.1-2.4keV). The temperature profile decreases from about 3keV in the outer parts to 1.2keV in the centre. Within a radius of 1.5Mpc the gas mass of the cluster is 0.51x10^14^Msun_ and the total