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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.
| The Palomar/MSU Nearby Star Spectroscopic Survey. IV. The Luminosity Function in the Solar Neighborhood and M Dwarf Kinematics
We have used new astrometric and spectroscopic observations to refinethe volume-complete sample of M dwarfs defined in previous papers inthis series. With the addition of Hipparcos astrometry, our revisedVC2 sample includes 558 main-sequence stars in 448 systems.Analysis of that data set shows no evidence of any systematic kinematicbias. Combining those data with a Hipparcos-based sample of AFGK dwarfswithin 25 pc of the Sun, we have derived the solar neighborhoodluminosity function, Φ(MV), for stars with absolutemagnitudes between -1 and +17. Using empirical and semiempiricalmass-MV relations, we transform Φ(MV) to thepresent-day mass function, ψ(M) (=dN/dM). Depending on themass-luminosity calibration adopted, ψ(M) can be represented byeither a two-component or a three-component power law. In either case,the power-law index α has a value of ~1.3 at low masses (0.1Msolar4)stars in the Hipparcos 25 pc sample are well represented bytwo-component Gaussian distributions, with ~10% of the stars in thehigher velocity dispersion component. We suggest that the lattercomponent is the thick disk, and we offer a possible explanation for therelatively low velocity dispersions shown by ultracool dwarfs.Based partly on observations made at the 60 inch (1.5 m) telescope atPalomar Mountain, which is jointly owned by the California Institute ofTechnology and the Carnegie Institution of Washington.
| Dwarf K and M stars of high proper motion found in a hemispheric survey
A recently completed visual/red spectral region objective-prism surveyof more than half the sky found some 2200 dwarf K and M stars ofnegligible proper motion (Stephenson, 1986). The present paper adds the1800-odd spectroscopically identified dwarfs that did prove to havesignificant proper motions. About half of these had previous spectralclassifications of some sort, especially by Vyssotsky (1952, 1956). Forthe great majority, the present coordinates are more accurate thanprevious data. The paper includes about 50 stars with unpublishedparallaxes, likely to have parallaxes of 0.05 arcsec or more. Combiningthe present data with the first paper suggests that the number oflow-proper-motion stars in that paper was not unreasonable.
| 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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| Takýmyýldýz: | Kova |
| Sað Açýklýk: | 23h08m15.21s |
| Yükselim: | -24°44'34.6" |
| Görünürdeki Parlaklýk: | 10.177 |
| Uzaklýk: | 19.881 parsek |
| özdevim Sað Açýklýk: | 0 |
| özdevim Yükselim: | 0 |
| B-T magnitude: | 11.669 |
| V-T magnitude: | 10.301 |
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