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Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes
To understand the formation and evolution of solar-type stars in thesolar neighborhood, we need to measure their stellar parameters to highaccuracy. We present a catalogue of accurate stellar parameters for 451stars that represent the HARPS Guaranteed Time Observations (GTO)“high precision” sample. Spectroscopic stellar parameterswere measured using high signal-to-noise (S/N) spectra acquired with theHARPS spectrograph. The spectroscopic analysis was completed assumingLTE with a grid of Kurucz atmosphere models and the recent ARES code formeasuring line equivalent widths. We show that our results agree wellwith those ones presented in the literature (for stars in common). Wepresent a useful calibration for the effective temperature as a functionof the index color B-V and [Fe/H]. We use our results to study themetallicity-planet correlation, namely for very low mass planets. Theresults presented here suggest that in contrast to their joviancouterparts, neptune-like planets do not form preferentially aroundmetal-rich stars. The ratio of jupiter-to-neptunes is also an increasingfunction of stellar metallicity. These results are discussed in thecontext of the core-accretion model for planet formation.Based on observations collected at La Silla Observatory, ESO, Chile,with the HARPS spectrograph at the 3.6-m telescope (072.C-0488(E)). FullTables 1 and 3 are only available in electronic form at the CDS vianonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/487/373
| The main sequence from F to K stars of the solar neighbourhood in SDSS colours
For an understanding of Galactic stellar populations in the SDSS filtersystem well defined stellar samples are needed. The nearby stars providea complete stellar sample representative for the thin disc population.We compare the filter transformations of different authors applied tothe main sequence stars from F to K dwarfs to SDSS filter system anddiscuss the properties of the main sequence. The location of the meanmain sequence in colour-magnitude diagrams is very sensitive tosystematic differences in the filter transformation. A comparison withfiducial sequences of star clusters observed in g', r', and i' show goodagreement. Theoretical isochrones from Padua and from Dartmouth havestill some problems, especially in the (r-i) colours.
| 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.
| K dwarfs and the chemical evolution of the solar cylinder
K dwarfs have lifetimes older than the present age of the Galactic disc,and are thus ideal stars for investigating the chemical evolution of thedisc. We have developed several photometric metallicity indicators for Kdwarfs, based on a sample of accurate spectroscopic metallicities for 34disc and halo G and K dwarfs. The photometric metallicities lead us todevelop a metallicity index for K dwarfs based only on their position inthe colour-absolute-magnitude diagram. Metallicities have beendetermined for 431 single K dwarfs drawn from the Hipparcos catalogue,selecting the stars by absolute magnitude and removing multiple systems.The sample is essentially a complete reckoning of the metal content innearby K dwarfs. We use stellar isochrones to mark the stars by mass,and select a subset of 220 of the stars, which is complete within anarrow mass interval. We fit the data with a model of the chemicalevolution of the solar cylinder. We find that only a modest cosmicscatter is required to fit our age-metallicity relation. The modelassumes two main infall episodes for the formation of the halo-thickdisc and thin disc, respectively. The new data confirm that the solarneighbourhood formed on a long time-scale of the order of 7 Gyr.
| The catalogue of nearby stars metallicities.
Not Available
| The evolution of asymptotic giant branch stars in the Large Magellanic Cloud. II - Spectroscopy of a complete sample
Spectra of 113 asymptotic giant branch (AGB) star candidatesconstituting six magnitude-limited, area-complete samples in the outerregions of the northern LMC have been obtained. Luminosity functionsconstructed from these data are well represented by an underlyingintermediate-mass AGB population, the product of continuous starformation over the last 3-4 Gyr, supplemented in some areas by moremassive red giant and supergiant stars, with a typical age of about 10to the 8th yr. Most stars with Mbol between -5 and -5.5 show evidencefor dredge-up of s-process elements, as do a smaller proportion in therange Mbol between -4.5 and -5. Only 10 percent of the sample, however,are C stars, and these are concentrated toward the Bar of the LMC. Noevidence has been found for envelope burning in any of the stars in thesample.
| Some Cross-Reference Lists for the Catalog of Possible Nearby Stars
Not Available
| Possible nearby stars brighter than tenth magnitude
Basic data are compiled for 447 stars brighter than 10th visualmagnitude which may be within 25 pc of the sun and are missing from boththe Gliese (1969) and the Woolley et al. (1970) catalogs of nearbystars. The list includes 245 stars with photometric parallaxes, 17 starswith trigonometric parallaxes, and nine stars with dynamical parallaxes,all of which parallaxes are at least 0.040 arcsec, as well as 176 likelycandidates. The stars are grouped into six categories according to thereliability of absolute-magnitude estimates and ranked within each groupon the basis of calculated distance. The distance estimates incorporatea kinematic correction to the photometric parallaxes which is based onthe size of a star's proper motion. A list of stars brighter than 10thmag which appear in the Gliese but not in the Woolley et al. catalog isalso provided to facilitate cross-reference with existing catalogs ofnearby stars.
| Nearby Star Data Published 1969-1978
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979A&AS...38..423G&db_key=AST
| 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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Observation and Astrometry data
| Constellation: | Telescopium |
| Right ascension: | 19h58m32.98s |
| Declination: | -54°56'12.8" |
| Apparent magnitude: | 8.535 |
| Distance: | 22.774 parsecs |
| Proper motion RA: | 106.9 |
| Proper motion Dec: | -120.9 |
| B-T magnitude: | 9.906 |
| V-T magnitude: | 8.649 |
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