The Milky Way has a giant stellar structure in the solar neighborhood, which has a size of ∼ 1 kpc, a mass of ∼ 106M⊙, and a ring-like distribution of young stars. Fundamental physical properties of this local enigmatic structure, known as the Gould belt (GB), have not been reproduced by previously proposed models. We first show that the local enigmatic structure can be formed about 30 Myr ago ...

This letter reports on the Galactic stellar structures that appear in the foreground of our CanadaFrance-Hawaii-Telecopse/MegaCam survey of the halo of the Andromeda galaxy. We recover the main sequence and main sequence turn-off of the Triangulum-Andromeda structure recently found by Majewski and collaborators at a heliocentric distance of ∼ 20 kpc. The survey also reveals another less populat...

The four equations of stellar structure are reformulated as two alternate pairs of variational principles. Different thermodynamic representations lead to the same hydromechanical equations, but the thermal equations require, not the entropy, but the temperature as the thermal field variable. Our treatment emphasizes the hydrostatic energy and the entropy production rate of luminosity produced ...

X-ray emission from stars in the cool half of the Hertzsprung-Russell diagram is generally attributed to the presence of a magnetic corona that contains plasma at temperatures exceeding 1 million K. Coronae are ubiquitous among these stars, yet many fundamental mechanisms operating in their magnetic fields still elude an interpretation through a detailed physical description. Stellar X-ray astr...

Soft X-ray surveys are very effective to study low-mass stellar populations in our Galaxy. Indeed stellar X-ray counts well complement optical stellar counts since they allow us to study spatial distributions and densities of main sequence stars as function of age. This capability is due to the strong dependence of X-ray luminosity on stellar age, especially during the main sequence life. As a ...

Among the problems still open in the study of stellar structure, we discuss in particular some issues related to the study of convection. We have recently built up complete stellar models, adopting a consistent formulation of convection both in the non gray atmosphere and in the interior, to be used for non adiabatic pulsational analysis, and discuss in some details two problems which have been...

The observable macroscopic properties of relativistic stars (whose equations of state are known) can be predicted by solving the stellar structure equations that follow from Einstein’s equation. For neutron stars, however, our knowledge of the equation of state is poor, so the direct stellar structure problem can not be solved without modeling the highest density part of the equation of state i...

We present the results from our deep optical imaging survey µ V lim ≈ 26 − 27 mag/ 2 ′′ of a morphologically selected sample of 72 edge-on disk galaxies. The question of the global structure of galactic stellar disks, especially the radial surface brightness profile at large galactocen-tric distances, is addressed. We find that typical radial profiles are better described by a two-slope exponen...

We present a time series of Doppler images of the RS CVn binary V711 Tauri from spectra taken during 57 consecutive nights in November and December 1996. VRI-band APT photometry throughout the entire observing season is used to support the Doppler imaging. A set of altogether 37 overlapping images from the Ca i-6439 line allows us to trace the latitudinal and longitudinal migration of individua...