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The effect of activity on stellar temperatures and radii
Context: Recent analyses of low-mass eclipsing binary stars haveunveiled a significant disagreement between the observations andpredictions of stellar structure models. Results show that theoreticalmodels underestimate the radii and overestimate the effectivetemperatures of low-mass stars but yield luminosities that accord withobservations. A hypothesis based upon the effects of stellar activitywas put forward to explain the discrepancies. Aims: In this paper westudy the existence of the same trend in single active stars and providea consistent scenario to explain systematic differences between activeand inactive stars in the H-R diagram reported earlier. Methods: Theanalysis is done using single field stars of spectral types late-K and Mand computing their bolometric magnitudes and temperatures throughinfrared colours and spectral indices. The properties of the stars insamples of active and inactive stars are compared statistically toreveal systematic differences. Results: After accounting for a numberof possible bias effects, active stars are shown to be cooler thaninactive stars of similar luminosity therefore implying a larger radiusas well, in proportions that are in excellent agreement with those foundfrom eclipsing binaries. Conclusions: The present results generalisethe existence of strong radius and temperature dependences on stellaractivity to the entire population of low-mass stars, regardless of theirmembership in close binary systems.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/478/507
| 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.
| Southern infrared proper motion survey. I. Discovery of new high proper motion stars from first full hemisphere scan
We present the first results from the Southern Infrared Proper MotionSurvey. Using 2 Micron All Sky Survey data along with that of theSuperCOSMOS sky survey we have been able to produce the first widefieldinfrared proper motion survey. Having targeted the survey to identifynearby M, L and T dwarfs we have discovered 70 such new objects withproper motions greater than 0.5''/yr with 10 of these having propermotions in excess of 1''/yr. The most interesting of these objects isSIPS1259-4336 a late M dwarf. We have calculated a trigonometricparallax for this object of π = 276 ± 41 milliarcsec yieldinga distance of 3.62±0.54 pc. We have also discovered a commonproper motion triple system and an object with a common proper motionwith LHS 128. The survey completeness is limited by the small epochdifferences between many 2MASS and UKI observations. Hence we onlyrecover 22% of Luyten objects with favourable photometry. However theLuyten study is itself unquantifiably incomplete. We discuss theprospect of enhancing the survey volume by reducing the lower propermotion limit.
| The Solar Neighborhood. X. New Nearby Stars in the Southern Sky and Accurate Photometric Distance Estimates for Red Dwarfs
Photometric (VJRCIC) and spectroscopic(6000-9500 Å) observations of high-proper-motion stars discoveredduring the first phase of the SuperCOSMOS RECONS (SCR) search are usedto estimate accurate distances to eight new nearby red dwarfs, includingprobable 10 pc sample members SCR 1845-6357 (M8.5 V at 4.6 pc), thebinary SCR 0630-7643AB (M6.0 V J at 7.0 pc), and SCR 1138-7721 (M5.0 Vat 9.4 pc). Distance estimates are determined using a suite of newphotometric color-MKs relations defined using arobust set of nearby stars with accurate VRIJHKs photometryand trigonometric parallaxes. These relations are used with optical andinfrared photometry to estimate distances on a uniform system (generallygood to 15%) for two additional samples of red nearby star candidates:several recently discovered members of the solar neighborhood and knownfaint stars with proper motions in excess of 1.0" yr-1 southof decl.=-57.5d. Of those without accurate trigonometric parallaxmeasurements, there are five stars in the first sample and three in thesecond that are likely to be within 10 pc. The two nearest are SO0253+1652 (M7.0 V at 3.7 pc) and DENIS 1048-3956 (M8.5 V at 4.5 pc).When combined with SCR 1845-6357, these three stars together representthe largest increase in the 5 pc sample in several decades. Red spectraare presented for the red dwarfs, and types are given on the RECONSstandard spectral system. Red spectra are also given for two new nearbywhite dwarfs for which we estimate distances from the photometry of lessthan 20 pc: WD 0141-675 (LHS 145; 9.3 pc) and SCR 2012-5956 (17.4 pc).WD 0141-675 brings the total number of systems nearer than 10 pcdiscussed in this paper to 12.
| The Solar Neighborhood. VIII. Discovery of New High Proper Motion Nearby Stars Using the SuperCOSMOS Sky Survey
Five new objects with proper motions between 1.0" and 2.6"yr-1 have been discovered via a new Research Consortium onNearby Stars (RECONS) search for high proper motion stars using theSuperCOSMOS Sky Survey. The first portion of the search, discussed here,is centered on the south celestial pole and covers declinations -90°to -57.5d. Photographic photometry from SuperCOSMOS and JHKsnear-infrared photometry from the Two Micron All Sky Survey for starsnearer than 10 pc are combined to provide a suite of newMKs-color relations useful for estimatingdistances to main-sequence stars. These relations are then used toderive distances to the new proper motion objects, as well as previouslyknown stars with μ>=1.0" yr-1 (many of which have notrigonometric parallaxes) recovered during this phase of the survey.Four of the five new stars have red dwarf colors, while one is a nearbywhite dwarf. Two of the red dwarfs are likely to be within the RECONS 10pc sample, and the white dwarf probably lies between 15 and 25 pc. Amongthe 23 known stars recovered during the search, there are threeadditional candidates for the RECONS sample that have no trigonometricparallaxes.
| 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 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
| 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 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 H-alpha and CA II lines in late-type stars
Observations of H-alpha and Ca II H and K in the chromospheres of 50main-sequence K and M stars are reported. The photospheric contributionto the integrated core flux in these lines is found to be more importantthan previously thought, and earlier estimates of the basal flux of cooldwarf stars are revised. The H-alpha data confirm the presence of bothan upper and a lower limit to the H-alpha equivalent width attained atany given spectral type. The maximum H-alpha absorption strengthdecreases gradually toward cooler stars while the maximum 'saturated'quiescent emission strength increases. The Ca II emission strength isrelated to the strength of the emission or absorption feature atH-alpha, but there is not a one-to-one correlation. The main results maybe explained in terms of photoionization and collisional control of thenon-LTE H-alpha source function. Several aspects of the structure andheating of the outer atmospheres of dwarf K and M stars are discussed.
| 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.
Not Available
| 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.
| Kinematical and orbital properties for selected southern high-velocity stars
Using the model of the Galaxy presented by Eggen, Lynden-Bell, andSandage (1962), plane galactic orbits have been calculated for severalsouthern high-velocity stars which possess parallax, proper motion, andradial velocity data. Extensive lists of both raw and computed data forthese stars are included. Published values of U-B and B-V for some ofthese stars were used in plots of each of the orbital parameters versusU-B, B-V, or the ultraviolet excess. Also, a comparison is made betweenthe H-R diagrams for the southern high-velocity star group and that ofM3, a globular cluster, and again for M67, an old open cluster. Thehigh-velocity star group is found to resemble an old open cluster morethan a globular cluster.
| Intermediate-band photometry of late-type stars. V - Calibration of indices
Additional data for several stellar groups and clusters are used toimprove a previously determined provisional relation betweenM1 photometric index and the parameter /Fe/H/(solar) as wellas to test the usefulness of the C1 photometric index forluminosity determinations. The data are for 43 members of the Wolf 630group, 14 members of the 61 Cygni group, 30 members of the Arcturusgroup, 14 members of Kapteyn's star groups, and various members of theHyades, 47 Tuc, NGC2420, Omega Cen, and an anonymous group of subdwarfs.It is found that in general the values of C1 only confirm agiant or dwarf classification without yielding accurate luminosities andthat the main contribution of C1 for disk objects is inisolating peculiar stars. The results also indicate that there is aluminosity effect in M1 for the strongest-lined stars andthat the values of M1 become distorted, probably by thepresence of TiO, for R-I larger than about +0.5 magnitude. An array forinterpolating /FE/H/(solar) from (R-I, M1) is constructed byadopting mean values of /Fe/H/(solar) equal to +0.1,-0.35, -0.6, and-1.8 for the Hyades, Wolf 630, Arcturus, and Kapteyn's star groups,respectively.
| Optical polarization of stars of galactic latitudes b-45 degres.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...23..125S&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
| 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
| Stellar Groups in the Old Disk Population
Not Available
| Positions for Some Nearby Faint Stars
Not Available
| Stellar parallaxes determined photographically at the Cape Observatory (Eighteenth List)
Not Available
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Miembro de los siguientes grupos:
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Datos observacionales y astrométricos
| Constelación: | Tucán |
| Ascensión Recta: | 00h57m19.74s |
| Declinación: | -62°14'44.2" |
| Magnitud Aparente: | 9.512 |
| Distancia: | 19.357 parsecs |
| Movimiento Propio en Ascensión Recta: | 1023.7 |
| Movimiento Propio en Declinación: | 127.7 |
| B-T magnitude: | 11.104 |
| V-T magnitude: | 9.644 |
Catálogos y designaciones:
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