Recent observations have revealed a superbubble associated with the young stellar cluster OCl 352 near the W4 H II region: a void in H I emission (Normandeau, Taylor, & Dewdney), and a bright shell in Hα emission (Dennison, Topasna, & Simonetti). We investigate the hypothesis that the bubble is blown by stellar winds from the O-type stars in the association. The Kompaneets approximation is adap...

Stellar magnetic activity – which has been observed in a diverse set of stars including the Sun – originates via a magnetohydrodynamic dynamo mechanism working in stellar interiors. The full set of magnetohydrodynamic equations governing stellar dynamos is highly complex, and so direct numerical simulation is currently out of reach computationally. An understanding of the bifurcation structure,...

I decompose the unstable growing modes of stellar disks to their Fourier components and present the physical mechanism of instabilities in the context of resonances. When the equilibrium distribution function is a non-uniform function of the orbital angular momentum, the capture of stars into the corotation resonance imbalances the disk angular momentum and triggers growing bar and spiral modes...

Studying the stellar populations in the outskirts of spiral galaxies can provide important constraints on their structure, formation, and evolution. To that end, we present VI photometry obtained with the Advanced Camera for Surveys for three fields located ∼ 20 − 30 in projected distance southeast of M33’s nucleus (corresponding to ∼ 4 − 6 visual scale lengths or ∼ 9 − 13 kpc in deprojected ra...

We simulate the effect of latitudinal variations in the location of star spots, as well as their magnetic field strength, on stellar angular momentum loss to the stellar wind. We use the Michigan solar corona global MagnetoHydroDynamic model, which incorporates realistic relation between the magnetic field topology and the wind distribution. We find that the spots’ location significantly affect...

The kinematics, structure, and stellar population properties in the centers of two brightest early-type galaxies of the Leo II group, NGC 3607 and NGC 3608, are studied by means of integral-field spectroscopy. The kinematically distinct areas in the centers of these galaxies, with radii of 6 and 5 respectively, are found also to be chemically distinct. These stellar structures are characterized...

The understanding and modeling of the structure and evolution of stars is based on statistical physics as well as on hydrodynamics. Today, a precise identification and proper description of the physical processes at work in stellar interiors are still lacking (one key point being that of transport processes) while the comparison of real stars to model predictions, which implies conversions from...

Helioseismology has allowed us to study the structure of the Sun in unprecedented detail. One of the triumphs of the theory of stellar evolution was that helioseismic studies had shown that the structure of solar models is very similar to that of the Sun. However, this agreement has been spoiled by recent revisions of the solar heavy-element abundances. Heavy element abundances determine the op...

Encircling the Milky Way at low latitudes, the Low Latitude Stream is a large stellar structure, the origin of which is as yet unknown. As part of the SEGUE survey, several photometric scans have been obtained that cross the Galactic plane, spread over a longitude range of 50◦ to 203◦. These data allow a systematic study of the structure of the Galaxy at low latitudes, where the Low Latitude St...

With the discovery of hundreds of exoplanets and a potentially huge number of Earth-like planets waiting to be discovered, the conditions for their habitability have become a focal point in exoplanetary research. The classical picture of habitable zones primarily relies on the stellar flux allowing liquid water to exist on the surface of an Earth-like planet with a suitable atmosphere. However,...