We review the models and results of simulations of self-gravitating, gaseous protoplanetary disks in binary star systems. These models have been calculated by three different groups with three different computational methods, two particle-based and one grid-based. We show that interactions with the companion star can affect the temperature distribution and structural evolution of disks, and dis...

The relation between the star formation rate and the kinetic energy increase in a region containing a large number of stellar sources is investigated as a possible prescription for star formation feedback in larger scale galaxy evolution simulations, and in connection with observed scaling relations for molecular clouds, extragalactic giant H II regions, and starburst galaxies. The kinetic ener...

I argue 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 over-expansion. This may occur when the photospheric (effective) temperature drops to Tp ∼ 2900 K, and because the opacity sharply increases as temperature decreases down ...

In the present-day universe, it appears that most, and perhaps all, massive stars are born in star clusters. It also appears that all star clusters contain stars drawn from an approximately universal initial mass function, so that almost all rich young star clusters contain massive stars. In this review I discuss the physical processes associated with both massive star formation and with star c...

We have conducted observations of the 12CO(J=1–0) and 12CO(J = 3–2) line emission of 74 major giant molecular clouds (GMCs) within the galactocentric distance of 5.1 kpc in the Local Group galaxy M33 [1]. The observations are part of the Nobeyama Radio Observatory M33 All-disk survey of Giant Molecular Clouds project (NRO MAGiC [2]). The spatial resolution is 100 pc. We detect 12CO(J = 3–2) emi...

Near infrared images of the Galactic giant H II region W43 reveal a dense stellar cluster at its center. Broad band JHK photometry of the young cluster and K−band spectra of three of its bright stars are presented. The 2 μm spectrum of the brightest star in the cluster is very well matched to the spectra of Wolf–Rayet stars of sub–type WN7. Two other stars are identified as O type giants or sup...

We calculate the orbital evolution of binary systems where the primary star is an evolved red giant branch (RGB) star, while the secondary star is a low mass main sequence (MS) star or a brown dwarf. The evolution starts when a tidal interaction causes the secondary to spiral-in. Either a common envelope (CE) is formed in a very short time, or the system reaches synchronization and the spiralin...

The Ori star-forming region presents a snapshot of a moderate-mass giant molecular cloud 1{2 Myr after cloud disruption by OB stars, with the OB stars, the low-mass stellar population, remnant molecular clouds, and the dispersed gas all still present. We have used optical photometry and multi-object spectroscopy for lithium absorption to identify 266 PMS stars in 8 degrees 2 of the region. We a...

B,V-CCD photometry has been obtained for stars in two fields in the NE part of the Large Magellanic Cloud (LMC) and photographic photometry, and a calibrating CCD sequence, for a third field. The colour-magnitude diagrams (CMDs) and luminosity functions (LFs) for main sequence (MS) and red giant (RG) stars in the fields are established. The red giant clumps (RGCs) are found to be bimodal and to...

WeBo 1 (PN G135.6+01.0), a previously unrecognized planetary nebula with a remarkable thinring morphology, was discovered serendipitously on Digitized Sky Survey images. The central star is found to be a late-type giant with overabundances of carbon and s-process elements. The giant is chromospherically active and photometrically variable, with a probable period of 4.7 days; this suggests that ...