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|The Hill stability of the possible moons of extrasolar planets|
The dynamical Hill stability has been derived for a full three-bodysystem composed of a binary moving on an inclined elliptical orbitrelative to a third body where the binary mass is very small comparedwith the mass of the third body. This physical situation arises in anumber of important astronomical contexts including extrasolar planetarysystems with a star-planet-moon configuration. The Hill stabilitycriterion against disruption and component exchange was applied to allthe known extrasolar planetary systems and the critical separation of apossible moon from the planet determined for moon/planet mass ratios of0.1, 0.01 and 0.001 assuming that the moon moves on a circular orbit. Itis clear that in those cases where the planet moves on a circular orbitabout the central star, the critical separation of the moon from theplanet does not change significantly as the value of the moon/planetmass ratio is reduced. In contrast, for eccentric systems there can bebig changes in the critical separation as the mass ratio decreases. Thevariation in size depends crucially on the size of the eccentricity ofthe planetary orbit.To determine the effect of an eccentrically orbiting moon, the Hillstability criterion was applied generally to the planet-moon binary fora range of moon/planet mass ratios assuming that the planet moved on acircular orbit around the central star. It was found that in all casesthe critical distance ratio increased, and hence the regions of Hillstability decreased as the binary eccentricity increased and also as theinclination of the third body to the binary was increased. The stabilityincreased slightly as the moon/planet ratio was decreased. Also as thebinary/third body mass ratio decreased the effects of the moon/planetmass ratio became less important and the stability curves tended tomerge. These types of changes make exchange or disruption of thecomponent masses more likely.
|UBV(RI)C JHK observations of Hipparcos-selected nearby stars|
We present homogeneous, standardized UBV(RI)C photometry forover 700 nearby stars selected on the basis of Hipparcos parallaxes.Additionally, we list JHK photometry for about half of these stars, aswell as L photometry for 86 of the brightest. A number of stars withpeculiar colours or anomalous locations in various colour-magnitudediagrams are discussed.
|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.
|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.
|Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics|
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (18.104.22.168) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
|The Palomar/MSU Nearby Star Spectroscopic Survey.II.The Southern M Dwarfs and Investigation of Magnetic Activity|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2799H&db_key=AST
|The general catalogue of trigonometric [stellar] paralaxes|
|Catalogue of Variable or Suspected Stars Nearby the Sun|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990A&AS...85..971P&db_key=AST
|BVRI photometry of the Gliese Catalogue stars|
Photoelectri BVRI photometry on the Cousins (Kron-Cape) system has beenobtained for many of the southern faint stars in the Gliese Catalog(1969). This extends the work of Cousins (1980) and provides a uniformset of data for the nearby stars. Several red dwarfs are noted, whichwere used to define the red end of the Cousins system.
|UBV (RI)c photometry of faint nearby stars.|
|Predicted infrared brightness of stars within 25 parsecs of the sun|
Procedures are given for transforming selected optical data intoinfrared flux densities or irradiances. The results provide R, T(eff)blackbody approximations for about 2000 of the stars in Woolley et al.'sCatalog of Stars (1970) within 25 pc of the sun, and additional whitedwarfs, with infrared flux densities predicted for them at ninewavelengths from 2.2 to 101 microns including the Infrared AstronomySatellite bands.
|UBV Photometry of 500 Southern Stars [erratum: 1973MNSSA..32...48C]|
|Standard magnitudes in the E regions.|
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|Proper motion Dec:||-198.4|
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