109 research outputs found
A young binary Brown Dwarf in the R-CrA star formation region
We present imaging and spectroscopic observations with HST (WFPC2, ACS/HRC
and STIS), VLT (FORS2) and Keck (HIRES) of the dM8 ultra-cool dwarf DENIS-P
J185950.9-370632, located in the R-CrA region. The presence of lithium
absorption at 670.8 nm and the strong Halpha emission indicate a young age and
a sub-stellar mass. Our diffraction-limited images resolve a companion at the
separation limit of HST/ACS (~0.06"). The 2.1 mJy flux in the LW2 filter
(5.0-8.5 microns) of the Infrared Space Observatory (see 1999A&A...350..883)
likely corresponds to an infrared excess, suggesting the presence of
circumstellar material. Proper motion and photometric measurements, as well as
the Halpha activity, confirm membership in the R-CrA star forming region. If
confirmed by further observations, DENIS-P J185950.9-370632 would be the first
accreting sub-stellar multiple system observed to date.Comment: 18 pages, 11 figures, 3 tables Version with full resolution figures
available on: ftp://ftp.mpe.mpg.de/people/hbouy/publications/DENIS1859.ps.g
The Interstellar Environment of our Galaxy
We review the current knowledge and understanding of the interstellar medium
of our galaxy. We first present each of the three basic constituents - ordinary
matter, cosmic rays, and magnetic fields - of the interstellar medium, laying
emphasis on their physical and chemical properties inferred from a broad range
of observations. We then position the different interstellar constituents, both
with respect to each other and with respect to stars, within the general
galactic ecosystem.Comment: 39 pages, 12 figures (including 3 figures in 2 parts
The effect of air pollution on stone decay: the decay of the Drachenfels trachyte in industrial, urban, and rural environments—a case study of the Cologne, Altenberg and Xanten cathedrals
Reefing of Quarter Spherical Ribbon Parachutes Used in the Ares I First Stage Deceleration System
Computational fluid dynamic studies of a solid and ribbon 12-gore parachute canopy in subsonic and supersonic flow
Computational fluid dynamic studies of 3-D, fixed geometry, gore-shaped parachute canopies are presented. Both solid and ribbon canopies with a 10% vent diameter are investigated. The flowfields analyzed are laminar and compressible, broaching both the subsonic and supersonic regimes. Results presented include characterization of the local and global flowfields and the internal and external canopy surface pressure distributions. The canopy surface pressure distributions may be utilized in subsequent structural analyses to assess the integrity of the parachute canopy fabric components
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