While most star formation occurs in giant molecular clouds, numerous small clouds and Bok globules are known to each harbor one or a few young stars. Studies of such isolated newborn stars offer insights into the star formation process unencumbered by the confusion that often complicates studies of richer star forming regions. In this chapter, a dozen Bok globules and small clouds have been sel...

Roughly half of nearby primary stars are members of binary or multiple systems, so the question of whether or not they can support the formation of planetary systems similar to our own is an important one in the search for life outside our solar system. Previous theoretical work has suggested that binary star systems might not be able to permit the formation of gas giant planets, because of the...

Direct imaging searches have begun to detect planetary and brown dwarf companions and to place constraints on the presence of giant planets at large separations from their host star. This work helps to motivate such planet searches by predicting a population of young giant planets that could be detectable by direct imaging campaigns. Both the classical core accretion and the gravitational insta...

For the eclipsing symbiotic binary FG Ser (AS 296) we have obtained a series of high resolution optical spectra. Combining the measured radial velocity variations for the red giant with published eclipse photometry gives a binary period of 650 days. We derive the radial velocity curve of the red giant, yielding the orbital parameters of the system and a mass function of mf = 0.039 M . We furthe...

A popular formation scenario for giant elliptical galaxies proposes that they might have formed from binary mergers of disk galaxies. Difficulties with the scenario that emerged from earlier studies included providing the necessary stellar mass and metallicity, maintaining the tight color-magnitude relation and avoiding phase space limits. In this paper we revisit the issue and put constraints ...

Two UV brights stars in globular clusters, ROA 5701 (ω Cen) and Barnard 29 (M 13) are analysed from high-resolution UV and optical spectra. The main aim is the measurement of iron abundances from UV spectra obtained with the HST-GHRS. In addition atmospheric parameters and abundances for He, C, N, O, and Si are derived from optical spectra (ESO CASPEC) for ROA 5701 or taken from literature for ...

I suggest that the behavior of the photospheric opacity in oxygen-rich (similar to solar abundance) upper asymptotic giant branch stars may cause these stars to substantially expand for a few thousand years. I term this process overexpansion. This may occur when the photospheric (effective) temperature drops to Tp ∼ 3000 K, and because the opacity sharply increases as temperature further decrea...

The M33 galaxy is a nearby, relatively metal-poor, late-type spiral. Its proximity and almost face-on inclination means that it projects over a large area on the sky, making it an ideal candidate for wide-field CCD mosaic imaging. Photometry was obtained for more than 10 6 stars covering a 74 ′ × 56 ′ field centered on M33. Main sequence (MS), supergiant branch (SGB), red giant branch (RGB) and...