5,471 research outputs found
The Origins and Early History of the Steamer Albatross, 1880–18
Spencer Fullerton Baird (Fig. 1), a noted systematic zoologist and builder of scientific institutions in 19th century America, persuaded the U.S. Congress to establish the United States Commission of Fish and Fisheries1 in March 1871. At that time, Baird was Assistant Secretary of the Smithsonian Institution. Following the death of Joseph Henry in 1878, he became head of the institution, a position he held until his own demise in 1887. In addition to his many duties as a Smithsonian official, including his prominent role in developing the Smithsonian’s Federally funded National Museum as the repository for governmental scientific collections, Baird directed the Fish Commission from 1871 until 1887.
The Fish Commission’s original mission was to determine the reasons and remedies for the apparent decline of American fisheries off southern New England as well as other parts of the United States. In 1872, Congress further directed the Commission to begin a large fish hatching program aimed at increasing the supply of American food
The angular resolution of the Pierre Auger Observatory
We discuss the angular resolution obtained for events registered with the
surface detector alone and for hybrid events, i.e., those observed
simultaneously by both the surface and fluorescence detectors. The angular
accuracy of the surface detector is directly extracted from the data itself and
on an event by event basis, and is given as a function of the number of
stations triggered by the event and of the zenith angle of the shower. We
compare the angular resolution of the surface detector obtained from hybrid
events with the one obtained from the surface detector alone.Comment: 6 pages, 8 figures. Presented at CRIS 2008, Malfa, Ital
The Effective temperature scale of M dwarfs from spectral synthesis
We present a comparison of low-resolution spectra of 60 stars covering the
whole M-dwarf sequence. Using the most recent PHOENIX BT-Settl stellar model
atmospheres (see paper by F. Allard, in this book) we do a first quantitative
compari- son to our observed spectra in the wavelength range 550-950 nm. We
perform a first confrontation between models and observations and we assign an
effective tempera- tures to the observed M-dwarfs. Teff-spectral type relations
are then compared with the published ones. This comparison also aims at
improving the models' opacities.Comment: To be published in the on-line version of the Proceedings of Cool
Stars 16 (ASP Conference Series) New version with bibliography correcte
Experimental study of the Ca2 1S+1S asymptote
The filtered laser excitation technique was applied for measuring transition
frequencies of the Ca B-X system from asymptotic levels of the
X ground state reaching . That level has an
outer classical turning point of about 20~\AA which is only 0.2 \rcm below the
molecular SS asymptote. Extensive analysis of the spectroscopic data,
involving Monte Carlo simulation, allowed for a purely experimental
determination of the long range parameters of the potential energy curve. The
possible values of the s-wave scattering length could be limited to be between
250 and 1000.Comment: 10 pages, 7 figure
High-contrast imaging of Sirius~A with VLT/SPHERE: Looking for giant planets down to one astronomical unit
Sirius has always attracted a lot of scientific interest, especially after
the discovery of a companion white dwarf at the end of the 19th century. Very
early on, the existence of a potential third body was put forward to explain
some of the observed properties of the system. We present new coronagraphic
observations obtained with VLT/SPHERE that explore, for the very first time,
the innermost regions of the system down to 0.2" (0.5 AU) from Sirius A. Our
observations cover the near-infrared from 0.95 to 2.3 m and they offer the
best on-sky contrast ever reached at these angular separations. After detailing
the steps of our SPHERE/IRDIFS data analysis, we present a robust method to
derive detection limits for multi-spectral data from high-contrast imagers and
spectrographs. In terms of raw performance, we report contrasts of 14.3 mag at
0.2", ~16.3 mag in the 0.4-1.0" range and down to 19 mag at 3.7". In physical
units, our observations are sensitive to giant planets down to 11 at
0.5 AU, 6-7 in the 1-2 AU range and ~4 at 10 AU. Despite
the exceptional sensitivity of our observations, we do not report the detection
of additional companions around Sirius A. Using a Monte Carlo orbital analysis,
we show that we can reject, with about 50% probability, the existence of an 8
planet orbiting at 1 AU. In addition to the results presented in the
paper, we provide our SPHERE/IFS data reduction pipeline at
http://people.lam.fr/vigan.arthur/ under the MIT license.Comment: 16 pages, 10 figures, accepted for publication in MNRA
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