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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.
| A photometric study of wide visual double stars. III - Wide visual double stars with F-type primaries
Fifty-one wide visual double stars with F-type primaries have beenobserved in the uvby, H-beta system. MK class, color excess, absolutemagnitude, effective temperature and distance have been derived fromcalibrations of the above systems. From the distances derived here andthe astrometric data, taken from the literature, it appears that atleast 75 percent of them can be 'physical pairs'. Nevertheless, about 33percent of the double stars in this sample seem to have a realseparation of their components larger than 0.01 parsecs. That means thatthese stars are not gravitationally bound, but they have a commonorigin. For this season, the values of their astrophysical parametersare usually very close together.
| A photometric study of wide visual double stars. II - Common proper motion double stars
A total of 82 common proper motion wide visual double stars have beenobserved using the uvby, H-beta systems. MK class, color excess,absolute magnitude, effective temperature, and distance have beenderived from calibrations of the above systems. From the distancesderived here and the astrometric data, taken from the literature, it wasfound that the percentage of physical binaries among the common propermotion wide double stars is significantly higher than the samepercentage among the wide visual double stars with significant relativeproper motion, but there are a lot of optical pairs among them as well.
| Maximum separations among cataloged binaries
The paper classifies many of the widest common-motion binaries listed inthe Aitken catalog and list 72 physical pairs with known photoelectricphotometry, 31 physical pairs without good photometry, and 27 opticalpairs. As a function of primary types, the physical systems have upperlimits to their separations that are exceeded by some of the opticalpairs. The fact that optical pairs occur with larger separations impliesthat the limits are real ones and not just catalog limitations. Thoselimits (in AU) are expressed by 2500 M1 exp 1.54 for B5-KO main-sequenceprimaries. The same limits hold for the Trapezium and hierarchicalsystems studied previously.
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | לויתן |
| התרוממות ימנית: | 02h25m44.96s |
| סירוב: | -21°18'47.8" |
| גודל גלוי: | 9.317 |
| מרחק: | 38.388 פארסק |
| תנועה נכונה: | 34.7 |
| תנועה נכונה: | 36.7 |
| B-T magnitude: | 9.889 |
| V-T magnitude: | 9.365 |
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