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Interstellar dust studies with TAUVEX
We propose to carry out studies on the properties of interstellar dustusing TAUVEX. Through the multi-band TAUVEX observations, particularlywith the use of filters optimized for extinction observations of the2175~AA~feature, combined with optical observations and 2MASS archiveddata, we can derive the extinction curve from UV to near-IR for starslocated in different regions and environments. The extinction curve is asensitive indicator of the properties of the interstellar dust and, assuch, will allow us to trace the properties and evolution of theinterstellar dust as a function of environment.
| Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample
We are obtaining spectra, spectral types, and basic physical parametersfor the nearly 3600 dwarf and giant stars earlier than M0 in theHipparcos catalog within 40 pc of the Sun. Here we report on resultsfor 1676 stars in the southern hemisphere observed at Cerro TololoInter-American Observatory and Steward Observatory. These resultsinclude new, precise, homogeneous spectral types, basic physicalparameters (including the effective temperature, surface gravity, andmetallicity [M/H]), and measures of the chromospheric activity of ourprogram stars. We include notes on astrophysically interesting stars inthis sample, the metallicity distribution of the solar neighborhood, anda table of solar analogs. We also demonstrate that the bimodal nature ofthe distribution of the chromospheric activity parameterlogR'HK depends strongly on the metallicity, andwe explore the nature of the ``low-metallicity'' chromosphericallyactive K-type dwarfs.
| Completeness of USNO-B for High Proper Motion Stars
I test the completeness of USNO-B detections of high proper motion(μ>180 mas yr-1) stars and the accuracy of itsmeasurements by comparing them to the revised New Luyten Two-Tenthscatalog of Salim & Gould. For 14.5~20 mas yr-1) may actuallyhave still larger errors than tabulated.
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| Interstellar C3 toward HD 210121
We report the detection of the 405 nm band of interstellar C3in absorption toward HD 210121. The abundance of triatomic carbon isapproximately 1/17 of that of diatomic carbon in the same diffusemolecular cloud. Rotational levels of C3 up to J=14 are seenin this cloud. The rotational excitation of C3 in theinterstellar medium may reflect a competition between inelasticcollisions, formation and destruction of the molecule, and radiativepumping in the far-infrared. The abundance of C3 is comparedwith chemical models. Attention is called to molecular properties thatneed to be better determined. Based on observations collected at theEuropean Southern Observatory, Paranal, Chile [ESO VLT-UT2 No65.I-0526(A)].
| Dwarf K and M stars in the southern hemisphere.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..486U&db_key=AST
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