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Spectrophotometric properties of pre-main-sequence stars: the ?Chamaeleontis cluster
We present a study of flux-calibrated low-resolution opticalspectroscopy of 10 stars belonging to eight systems in the ~5-Myr-old?Chamaeleontis (?Cha) pre-main-sequence (PMS) starcluster. Using synthetic broad-band colours, narrow-band continuum,atomic and molecular lines derived from the spectra, we compare the?Cha stars to a slightly older PMS cluster, the ~8-Myr-old?Cha cluster and to main-sequence dwarfs. Using synthetic VRIcolours and other indices, we find that the relationship betweenbroad-band colours and spectroscopic temperature indicators for?Cha cluster members is indistinguishable from that of Gyr-olddwarfs. This result is identical to that found earlier in ?Cha.Gravity-sensitive line indices place the cluster between the giant anddwarf sequences, and there is clear evidence that ?Cha starshave lower surface gravity than ?Cha stars. This result isconsistent with ?Cha being the slightly younger PMS association,a few Myr younger according to the Hertzsprung-Russell (HR) diagramplacement of these two clusters and comparison with PMS evolutionarygrids. Late M-type ?Cha cluster members show a B-band fluxexcess of ~0.2mag compared to observations of standard dwarfs, whichmight be related to enhanced magnetic activity. A similar level ofexcess B-band emission appears to be a ubiquitous feature of low-massmembers of young stellar populations with ages less than a few hundredMyr, a very similar time-scale to the PMS phase of elevated relativeX-ray luminosity.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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.
| Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalog
We present refined coordinates and proper-motion data for the highproper-motion (HPM) stars in the Luyten Half-Second (LHS) catalog. Thepositional uncertainty in the original Luyten catalog is typicallygreater than 10" and is often greater than 30". We have used the digitalscans of the POSS I and POSS II plates to derive more accurate positionsand proper motions of the objects. Out of the 4470 candidates in the LHScatalog, 4323 objects were manually reidentified in the POSS I and POSSII scans. A small fraction of the stars were not found because of thelack of finder charts and digitized POSS II scans. The uncertainties inthe revised positions are typically ~2" but can be as high as ~8" in afew cases, which is a large improvement over the original data.Cross-correlation with the Tycho-2 and Hipparcos catalogs yielded 819candidates (with mR<~12). For these brighter sources, theposition and proper-motion data were replaced with the more accurateTycho-2/Hipparcos data. In total, we have revised proper-motionmeasurements and coordinates for 4040 stars and revised coordinates for4330 stars. The electronic version of the paper5 contains the updated information on all 4470stars in the LHS catalog.
| 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 (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Astrometric positions of stars with high proper motions in the Southern Hemisphere
Several stars with large proper motions, cited by W.J. Luyten, wereincluded in the preliminary programme for the HIPPARCOS mission. Whenperforming preparatory measurements of plates, difficulties wereencountered in identifying certain of these stars when relying only onpublished coordinates. We have taken advantage of this work whichrelates to the southern sky in order to determine the astrometricposition of the greatest possible number of these objects, even forthose which were not included in the programme. Catalogue is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The Stellar Content of Star Stream I
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111.1615E&db_key=AST
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Ca II H and K Filter Photometry on the UVBY System. II. The Catalog of Observations
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....109.2828T&db_key=AST
| The general catalogue of trigonometric [stellar] paralaxes
Not Available
| Far infrared properties of late type dwarfs. Infrared fluxes of K & M dwarfs
IRAS fluxes/upper limits are presented for a large sample of K and Mdwarfs. Good agreement is found between the 12 micrometer fluxes andthose derived from the photospheric models of Mould (1976).Relationships between the optical and infrared colors are derived. Theactive dMe/dKe stars appear systematically brighter in the infraredcompared with the less active dM/dK stars, which could be attributed tomore efficient nonradiative heating in their atmosphere. Any systematicdifferences found in our results when compared with those obtained fromprevious studies are attributed to the different analysis packages used.
| The importance of surface inhomogeneities for K and M dwarf chromospheric fluxes
We present published and archived spectroscopic and spectrophotometricdata of H-alpha, Ca II, Mg II, and X-rays for a large sample of K and Mdwarfs. The data set points to the importance that surfaceinhomogeneities have in the flux luminosity diagrams in these late-typedwarfs, irrespective of whether the Balmer lines are in emission orabsorption. Although supporting the fact that cooler stars exhibitincreasing levels of surface activity, evident through an increasingincidence of Balmer emission, surface inhomogeneities, or variations inthe local temperature and density structure, at the chromospheric level,dominate the total Ca II and Mg II fluxes. We show that the flux-fluxand luminosity-luminosity relations indicate differing extents ofinhomogeneity from the chromosphere through to the corona. A goodcorrelation between Ca II and Mg II fluxes indicates that they areformed in overlapping regions of the chromosphere, so that thecontribution of surface inhomogeneities is not evident from thisparticular flux-flux diagram. In the region of the upper chromospherethrough to the transition and corona, the correlation between Ly-alphaand X-ray fluxes indicates regions with similar levels of arealinhomogeneity. This appears to be uncorrelated with that at thechromospheric level.
| Chromospheric heating in late-type dwarfs - Acoustic or magnetic?
Mg II h and k fluxes for 69 K and 88 M dwarfs have been analyzed. Anempirical lower limit is found in the Mg II flux, extended down to thelatest spectral types. Based on the data presented here it is themagnetic component that dominates the emission from the atmosphere ofcool dwarfs, especially the M dwarfs. It, however, coexists with anacoustically heated component, which can only be identified in the starswith the lowest fluxes in the flux-color diagram, these stars possiblybeing the slowest rotators. Data for the dM(e) stars, i.e., those starswith zero H-alpha, show that these are divided into two classes: (1) aninactive M dwarf star with very weak chromospheric heating, perhaps onlyby acoustic waves; and (2) an intermediate chromospheric activity stardominated by magnetic heating.
| 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 photoelectric catalogue (1986). II - Analysis
The UBV photoelectric data of the stars presenting several entries inthe 1986 edition of the UBV catalog have been systematicallyintercompared, and this paper presents a discussion of the stars forwhich discrepancies larger than 0.2 mag were found. Thirty-six probablyvariable stars have been detected, among which 18 are Be stars. Sixtyfurther stars present differences in the V magnitude larger than 0.2mag. Sixteen stars already appear in the NSV catalog. Although manyproblems are probably due to poor observations, new (eclipsing) variablestars may be found in this sample. Complete disagreement is foundbetween the values published from two independent sources in 34 cases. Afirst analysis of the quality of the UBV data shows that 65 percent ofthe differences in the V magnitude and in U-B color, for respectively11,500 and 7200 stars with two sources of data, are smaller than 0.04.The scatter on the B-V index appears to be smaller, since the samepercentage reaches 79 percent.
| UBV Photoelectric Photometry Catalogue (1986). III Errors and Problems on DM and HD Stars
Not Available
| Luminosities, abundances, and motions of stars brighter than visual magnitude 15.1 and annual proper motions larger than one-half arcsecond
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987AJ.....93..393E&db_key=AST
| Catalog of proper-motion stars. III - Stars brighter than visual magnitude 15.1, south of declination +30 deg, and with annual proper motion between 0.5 and 0.7 arcsec
A catalog of (VRI) photometry for the some one thousand stars withannual proper motion between 0.5 and 0.7 arcsec, brighter than visualmagnitude 15.1, and south of declination +30 deg is presented. Theavailable proper-motion and radial-velocity data are also summarized.
| Chromosphere emission in late main sequence stars of different masses and ages
Results on observations of emission components in the H and K lines ofCa II and in the h and k lines of Mg II of main sequence late typestars, belonging to the young Hyades and Coma clusters and the oldmoving groups, Zeta Her, epsilon Ind, sigma Pup, and Arcturus arepresented. An approach to obtain integrated emission fluxes of Mg IIlines from IUE low resolution spectra of solar and late type MS stars isproposed. From a preliminary analysis of the Ca II and Mg II emissionluminosity, the relation L(chrom) alpha mass upsilon is found to bevalid at least for young cluster stars, with upsilon = 4.34 for theHyades. A probable dependence of the chromospheric emission luminosityfrom the metallic abundance in the old disk population stars isdiscussed.
| G. P. Kuiper's spectral classifications of proper-motion stars
Spectral classifications are listed for over 3200 stars, mainly of largeproper motion, observed and classified by Kuiper during the years1937-1944 at the Yerkes and McDonald Observatories. While Kuiper himselfpublished many of his types, and while improved classifications are nowavailable for many of these stars, much of value remains. For many ofthe objects, no other spectral data exist.
| 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.
| New light on faint stars. I - The luminosity function in the solar neighbourhood
From photoelectric photometry of red dwarf stars identified in anobjective prism survey, a magnitude-limited complete sample has beendefined. Applying photometric parallaxes, calibrated for theKron-Cousins system by observations of trigonometric parallax stars,this sample is used to determine the space densities of stars withabsolute magnitudes between + 7 and + 12. The resultant luminosityfunction is consistent with the Luyten and Wielen functions for thesolar neighbourhood. An analysis of the stellar kinematics shows littlesignificant evidence of a substantial local population of low spacemotion M-dwarfs.
| Studies of late-type dwarfs. II - A photometric metal abundance index and application to galactic evolution
Photometric and radial-velocity data are presented for 37 southernlate-type dwarf stars. With data from the literature for a larger sampleof stars, it is shown that late-type subdwarfs have deficiencies oflight in the blue region of the spectrum when compared with normal starsof the same (R - I) color. A photometric index that is a measure of theblue deficiency is defined and shown to correlate with the ultravioletexcess. The photometric index is also shown to correlate with thedynamical quantities of the star's orbit in the Galaxy.
| 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
| UBV Photometry of 500 Southern Stars [erratum: 1973MNSSA..32...48C]
Not Available
| The ζ Herculis, σ Puppis, ∈ Indi, and η Cephei Groups of Old Disk Population Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971PASP...83..251E&db_key=AST
| Luminosities, Temperatures, and Kinematics of K-Type Dwarfs
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971ApJS...22..389E&db_key=AST
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Dades d'Observació i Astrometria
| Constel·lació: | Centaurus |
| Ascensió Recta: | 14h21m23.19s |
| Declinació: | -40°23'38.2" |
| Magnitud Aparent: | 9.011 |
| Distancia: | 27.45 parsecs |
| Moviment propi RA: | -561.8 |
| Moviment propi Dec: | -69 |
| B-T magnitude: | 10.463 |
| V-T magnitude: | 9.131 |
Catàlegs i designacions:
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