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Intermediate-Brightness Equatorial Spectrophotometric Standards
We have obtained spectral energy distributions for 41 7m 8m stars nearthe celestial equator (δ=±3°). The λλ31007600 Å spectral range is studied with a spectral resolution of 50Å. The relative rms error in the visible is 1 2%, increasing to 35% towards the edges of the wavelength interval studied. All stars arereferenced to a single standard, the circumpolar star HD 221525. Thesynthetic colors of common stars are compared with those observed infour photometric systems: U BV, W BV R, uvby, and that of the TYCHOcatalog. The program stars are recommended as secondaryspectrophotometric standards.
| Near-Infrared Spectroscopy of the Cool Brown Dwarf, SDSS 1624+00
Using the Subaru Telescope, we have obtained multiple near-infraredspectra of the cool brown dwarf, SDSS 1624+00 (J162414.37+002915.8), insearch of spectral variability in an 80 minute time span. We have foundthe suspected variability of water vapor absorption throughout theobservations, which requires a confirmation with a longer time baseline.After coadding the spectra, we have obtained a high-quality spectrumcovering from 1.05 to 1.8 mu m. There are three kinds of spectralindicators, the water vapor bands, methane band and K I lines at 1.243and 1.252 mu m, which can be used to study the temperature and thepresence of dust. We compare the spectra of SDSS 1624+00 and Gliese229B, while paying special attention to these indicators. The shallowerwater vapor absorption of SDSS 1624+00 indicates that it is warmerand/or dustier. The shallower methane absorption suggests that SDSS1624+00 is warmer. We interpret the deeper K I lines in SDSS 1624+00 asbeing the result of its higher temperature. With the help of modelspectra, we conclude that SDSS 1624+00 is warmer and dustier than Gliese229B. For the first time in a cool brown dwarf, a finite flux is seen atthe bottom of the water vapor band between 1.34 and 1.42 mu m, whichmeans that the 1.4 mu m band of water can be completely observed fromthe ground.
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
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