The importance of understanding the current and historical galactic environments of cool stars is discussed. The penetration of interstellar gas into a stellar astrosphere is a function of the interaction of the star with the interstellar cloud surrounding the star, and this factor needs to be understood if an efficient search for life-bearing planets is to be made. For the Sun, both current an...

We present new observations of the binary Sirius A / Sirius B performed with HST-GHRS. Two interstellar clouds are detected on this sightline, one of them being identified as the Local Interstellar Cloud (LIC), in agreement with previous HST-GHRS observations of Sirius A (Lallement et al. 1994). The interstellar structure of this sightline, which we assume is the same toward both stars (separat...

We present new observations of the binary Sirius A / Sirius B performed with HST-GHRS. Two interstellar clouds are detected on this sightline, one of them being identified as the Local Interstellar Cloud (LIC), in agreement with previous HST-GHRS observations of Sirius A (Lallement et al. 1994). The interstellar structure of this sightline, which we assume is the same toward both stars (separat...

It appears that the majority of rapidly-, well-localized gamma-ray bursts with undetected, or dark, optical afterglows, or ‘dark bursts’ for short, occur in clouds of size R ∼> 10L 1/2 49 pc and mass M ∼> 3× 10 L49 M⊙, where L is the isotropic-equivalent peak luminosity of the optical flash. We show that clouds of this size and mass cannot be modeled as a gas that is bound by pressure equilibri...

The characterization of interstellar chemical inventories provides valuable insight into the and physical processes in astrophysical sources. discovery new molecules becomes increasingly difficult as number viable species grows combinatorially, even when considering only most thermodynamically stable. In this work, we present a novel approach for understanding modeling by combining methodologie...

We have used archival far-ultraviolet spectra from observations made by the Space Telescope Imaging Spectrograph (STIS) of the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer (FUSE ) to determine the column densities and rotational excitation temperatures for carbon monoxide and molecular hydrogen, respectively, along the lines of sight to 23 Galactic O and B stars. The si...

Gravitational collapse of the cylindrical elongated cloud is studied by numerical magnetohydrodynamical simulations. In the infinitely long cloud in hydrostatic configuration, small perturbations grow by the gravitational instability. The most unstable mode indicated by a linear perturbation theory grows selectively even from a white noise. The growth rate agrees with that calculated by the lin...

Turbulent fragmentation determines where and when protostellar cores form, and how they contract and grow in mass from the surrounding cloud material. This process is investigated, using numerical models of molecular cloud dynamics. Molecular cloud regions without turbulent driving sources, or where turbulence is driven on large scales, exhibit rapid and efficient star formation in a clustered ...