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Further observations of Hipparcos red stars and standards for UBV(RI)C photometry
We present homogeneous and standardized UBV(RI)C JHKphotometry for over 100 M stars selected from an earlier paper on thebasis of apparent photometric constancy. L photometry has been obtainedfor stars brighter than about L = 6. Most of the stars have asubstantial number of UBV(RI)C observations and, it is hoped,will prove useful as red supplementary standards. Additionally, we listJHK photometry for nearly 300 Hipparcos red stars not selected asstandards, as well as L photometry for the brightest stars.
| The Chromospheric Activity and Ages of M Dwarf Stars in Wide Binary Systems
We investigate the relationship between age and chromospheric activityfor 139 M dwarf stars in wide binary systems with white dwarfcompanions. The age of each system is determined from the cooling age ofits white dwarf component. The current limit for activity-age relationsfound for M dwarfs in open clusters is 4 Gyr. Our unique approach tofinding ages for M stars allows for the exploration of this relationshipat ages older than 4 Gyr. The general trend of stars remaining activefor a longer time at a later spectral type is confirmed. However, ourlarger sample and greater age range reveal additional complexity inassigning age based on activity alone. We find that M dwarfs in widebinaries older than 4 Gyr depart from the loglinear relation forclusters and are found to have activity at magnitudes, colors, andmasses that are brighter, bluer, and more massive than predicted by thecluster relation. In addition to our activity-age results, we presentthe measured radial velocities and complete space motions for 161 whitedwarf stars in wide binaries.Based on observations obtained with the Apache Point Observatory 3.5 mtelescope, which is owned and operated by the Astrophysical ResearchConsortium; the Cerro Tololo Inter-American Observatory 4.0 m telescope,which is operated by the Association of Universities for Research inAstronomy (AURA), Inc., under a cooperative agreement with the NationalScience Foundation (NSF) as part of the National Optical AstronomyObservatory (NOAO), which also operates Kitt Peak National Observatoryin Tucson, Arizona; and the SARA Observatory 0.9 m telescope at KittPeak, which is owned and operated by the Southeastern Association forResearch in Astronomy (http://www.saraobservatory.org).
| 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.
| UBV(RI)C photometry of Hipparcos red stars
We present homogeneous and standardized UBV(RI)C photometryfor nearly 550 M stars selected from the Hipparcos satellite data baseusing the following selection criteria: lack of obvious variability (noHipparcos variability flag); δ<+10°(V-I)>1.7 and Vmagnitude fainter than about 7.6. Comparisons are made between thecurrent photometry, other ground-based data sets and Hipparcosphotometry. We use linear discriminant analysis to determine aluminosity segregation criterion for late-type stars, and principalcomponent analysis to study the statistical structure of the colourindices and to calibrate absolute magnitude in terms of (V-I) for thedwarf stars. Various methods are used to determine the mean absolutemagnitude of the giant stars. We find 10 dwarf stars, apparentlypreviously unrecognized (prior to Hipparcos) as being within 25pc,including five within 20pc.
| 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.
| Meeting the Cool Neighbors. II. Photometry of Southern NLTT Stars
We present BVRI photometry of 180 bright, southern nearby-starcandidates. The stars were selected from the New Luyten Two-Tenthsproper-motion catalog based on optical/infrared colors, constructed bycombining Luyten's mr estimates with near-infrared photometryfrom the Two Micron All Sky Survey. Photometric parallaxes derived fromV-Ks, V-I, and I-J colors, combined with the limitedavailable astrometry, show that as many as 108 stars may lie within 20pc of the Sun. Of these, 53 are new to nearby-star catalogs, includingthree within 10 pc of the Sun.
| 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
| The Palomar/MSU Nearby-Star Spectroscopic Survey. I. The Northern M Dwarfs -Bandstrengths and Kinematics
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.1838R&db_key=AST
| Statistical studies of visual double and multiple stars. II. A catalogue of nearby wide binary and multiple systems.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994RMxAA..28...43P&db_key=AST
| 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.
| Parallaxes and proper motions. XIX - The subdwarf sequence
Parallaxes and proper motions are presented for 19 stars in 15 starfields. Four of the stars were discovered in the course of the measuresto have significantly large proper motions and the data for them areincluded in the tables. The other 15 are all stars considered to besubluminous. Photometric and metallicity data for most of them arepresented. They appear not to conform to a straight linear relationbetween (FE/H) determined from the measured ultraviolet excess and theabsolute magnitude corrected to a B-V color of 0.6.
| Chromospheric diagnostics in late-type stars
Moderate and low resolution spectroscopic observations of late typedwarfs covering a broad range of activity are presented. The strength ofthe TiO band in 4762 A is used for spectral classification. Calibratedfluxes for the Balmer and the Ca II H and K lines are derived. H-alphaequivalent widths are given for those stars where the line is inabsorption as well as those in emission. It is confirmed that stars withno detectable or very weak H-alpha do exist. It is also shown that starswith very weak or no detectable emission in Ca II H and K also exist,this occurring preferentially in late M dwarfs. Although this can beexplained in terms of reduced nonradiative heating in the chromosphere,the results cannot be conclusive due to the limited resolution of thedata.
| 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
| Optical and infrared photometry of dwarf M and K stars
Absolute U, B, V, R, I, J, H, K, and L photometry are given for a groupof dwarf M and K stars. Using black-body fits to the data, bolometricluminosities and radii are derived. The derived bolometric luminositiesare good to + or - 10 percent and the effective temperatures to + or -100 K. A comparison is made with the values derived by other authors.The derived radii are 14 percent smaller than those derived from therevised Barnes et al. (1978) relation involving (V - R).
| 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.
| A digitized version of the NLTT Catalogue of proper motions
An optically scanning data-entry machine and various manual techniquesare used to digitize the NLTT Catalogue and the first supplement to theNLTT Catalogue. Included in the catalog are stars found on over 800Palomar proper-motion survey plates to have relative annual propermotions exceeding 0.18 arcsec. The supplement contains data for 398stars having motions larger than 0.179 arcsec annually.
| UBV (RI)c photometry of faint nearby stars.
Not Available
| Identifications and limited spectroscopy for Luyten common proper motion stars with probable white dwarf components. I - Pair brighter than 17th magnitude
Identifications are provided for 103 bright Luyten common proper motion(CPM) stellar systems with m(pg) less than 17.0 mag containing likelywhite dwarf (WD) components. New spectral types are presented for 55components, and spectral types for 51 more are available in theliterature. With the CPM systems previously published by Giclas et al.(1978), the Luyten stars provide a uniform sample of nearly 200 pairs ormultiples brighter than 17h magnitude. Selection effects biasing thecombined samples are discussed; in particular, evidence is presentedthat fewer than 1 percent of wide WD binaries have been detected.
| Spectroscopic observations of cool degenerate star candidates
Spectroscopic observations are reported for 23 Luyten Half-Seconddegenerate star candidates and for 13 Luyten-Palomar commonproper-motion pairs containing possible degenerate star components.Twenty-five degenerate stars are identified, 20 of which lack previousspectroscopy. Most of these stars are cool - Luyten color class g orlater. One star, LP 77-57, shows broad continuum depressions similar tothose in LHS 1126, which Liebert and Dahn attributed to pressure-shiftedC2. A second degenerate star, LHS 290, exhibits apparent strong Swanbands which are blueshifted about 75 A. Further observations, includingpolarimetry and photometry, are required to appraise the spectroscopicpeculiarities of these stars. Finally, five cool, sharp-lined DA whitedwarfs have been observed to detect lines of metals and to determineline strengths. None of these DAs show signs of Mg b or the G band, andfour show no evidence of Ca II K. The attempt to detect Ca MI in thefifth star, G199-71, was inconclusive.
| Chromospheric activity, kinematics, and metallicities of nearby M dwarfs
Attention is given to the results of more than 1000 observations ofabout 200 Gliese (1969) catalog M dwarfs, whose BVRIJHK photometry isbelieved to be accurate to 0.015 mag in each bandpass. An analysis ofthese data indicates that the H-alpha equivalent widths are a usefulchromospheric indicator for M dwarfs; as the chromosphere increases instrength, the H-alpha absorption equivalent width first increases, thendecreases, and H-alpha finally goes into emission, as predicted by Gramand Mullan (1979) for M dwarf chromospheres. The present JHK photometryis used to identify stars with metallicities that are significantlydifferent from that of the sun. It is noted that dMe stars in thissample generally have young disk motions, are more luminous than dMstars of the same color, and have B-V colors that are too blue for theirV-I color.
| Dwarf K and M stars of high proper motion found in a hemispheric survey
A recently completed visual/red spectral region objective-prism surveyof more than half the sky found some 2200 dwarf K and M stars ofnegligible proper motion (Stephenson, 1986). The present paper adds the1800-odd spectroscopically identified dwarfs that did prove to havesignificant proper motions. About half of these had previous spectralclassifications of some sort, especially by Vyssotsky (1952, 1956). Forthe great majority, the present coordinates are more accurate thanprevious data. The paper includes about 50 stars with unpublishedparallaxes, likely to have parallaxes of 0.05 arcsec or more. Combiningthe present data with the first paper suggests that the number oflow-proper-motion stars in that paper was not unreasonable.
| 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.
| Catalogue of Metal-Deficient F-Stars to M-Stars - Part One - Stars Classified Spectroscopically - Supplement One
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.
| Studies of late-type dwarfs. V - Theoretical models for lower main-sequence stars
New theoretical stellar models for the lower end of the main sequencehave been computed for a wide range in metallicity. These models arebased on new low-temperature opacities, which include the contributionsfrom the most important molecules, as well as published modelatmospheres, which guided the choice of surface boundary conditions.While the present treatment of the nonideal gas effects is onlyapproximate, reasonable agreement is found with those models comuputedwith a more sophisticated equation of state for solar-like composition.The results are compared with the available observations of late-typedwarfs on both the (M(bol), log T(eff)- and (M(bol), mass)-planes, andsatisfactory agreement is found. In particular, some preliminaryobservational data appear to be consistent with the model predictionthat the most metal-poor subdwarfs should be up to 3 mag subluminous onthe theoretical H-R diagram.
| A spectroscopic survey of 113 nearby red dwarf stars
A spectroscopic survey of nearby red dwarf stars has been undertakenwith the primary objective of searching for flare stars, which would beexpected to have H alpha in emission. A by-product of this survey hasbeen the classification of the stars on the revised MK system and theidentification of possible subdwarfs. The candidate stars were chosenfrom the list of stars with proper motion greater than 1 arc sec peryear and V magnitude brighter than 15 with the additional requirementsthat the stars be south of declination 0 deg and have R-I 0.65. Thelatter essentially excludes all stars with spectral type earlier thanK7. A few extra stars were also observed, most of these being stars withMK classifications.
| Catalogs of proper-motion stars. I - Stars brighter than visual magnitude 15 and with annual proper motion of 1 arcsec or more
Abstract image available at:http://adsabs.harvard.edu/abs/1979ApJS...39...89E
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Dades d'Observació i Astrometria
| Constel·lació: | Hydra |
| Ascensió Recta: | 10h45m39.09s |
| Declinació: | -19°06'51.8" |
| Magnitud Aparent: | 11.052 |
| Moviment propi RA: | -1869.2 |
| Moviment propi Dec: | -607.6 |
| B-T magnitude: | 12.952 |
| V-T magnitude: | 11.209 |
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