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.
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Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
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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.
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Calibrating M Dwarf Metallicities Using Molecular Indices
We report progress in the calibration of a method to determine cooldwarf star metallicities using molecular band strength indices. Themolecular band index to metallicity relation can be calibrated usingchemical abundances calculated from atomic-line equivalent widthmeasurements in high-resolution spectra. Building on previous work, wehave measured Fe and Ti abundances in 32 additional M and K dwarf starsto extend the range of temperature and metallicity covered. A test ofour analysis method using warm star-cool star binaries shows we cancalculate reliable abundances for stars warmer than 3500 K. We have usedabundance measurements for warmer binary or cluster companions toestimate abundances in six additional cool dwarfs. Adding stars measuredin our previous work and others from the literature provides 76 starswith Fe abundance and CaH2 and TiO5 index measurements. The CaH2molecular index is directly correlated with temperature. TiO5 depends ontemperature and metallicity. Metallicity can be estimated to within+/-0.3 dex within the bounds of our calibration, which extends fromroughly [Fe/H]=+0.05 to -1.0, with a limited extension to -1.5.
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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.
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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
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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.
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Photometry of dwarf K and M stars
An observational program using UBVRI photometry is presented for 688stars from among the dwarf K and M stars already found spectroscopicallyby Vyssotsky (1958). Of these, 211 have not been observedphotometrically. These observations were obtained over a period ofseveral years at the Kitt Peak National Observatory using a GaAsphotomultiplier with an 0.9 m reflector. Based on night-to-nightvariations in the measures of individual stars, the internal errors maybe estimated to be roughly 0.01 mag for the colors and 0.015 for the Vmagnitudes. The photometric parallaxes reported for each star werecomputed in the manner discussed by Weis (1986).
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Activity in Late Type Stars - Part Eight - the Nature of the Dm/e or Zero Hα Stars
Abstract image available at:http://adsabs.harvard.edu/abs/1993A&A...272..495B
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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.
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VRI photometry of late dwarf common proper motion pairs
VRI photometry and photometric distance moduli are presented for 266late dwarf common proper motion pairs. From the distance modulusdifferences between the components of each pair, it is inferred that atleast 56 percent of the pairs contain one or more additional stellarcomponents. The maximum separation of M dwarf binaries appears to be ofthe order 10,000-20,000 AU.
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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.
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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.
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Ly-alpha and MG II H and K fluxes in a sample of dwarf M stars
Ly-alpha and Mg II fluxes are given for a group of M dwarfs. TheLy-alpha and Mg II lines were extracted from low resolution spectrataken with the IUE satellite. The Ly-alpha line is shown to be animportant source of radiative losses in dMe chromospheres, being atleast a factor of two more important than Mg II. Overall it contributesapproximately 25 percent of the total chromospheric losses, about thesame as the more commonly observed H-alpha line. In order to haveapproximately equal contributions from these lines, one requires eithera plateau region in the lower transition region or different fillingfactors for the two lines. In dM stars, Ly-alpha is approximately thesame magnitude as Mg II.
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Flux-flux relation - MG II H and K versus X-rays in dwarf M and K stars
Surface X-ray and Mg II h and k fluxes are presented for a group of dMe,dKe, dM, and dK stars. No correlation is apparent between the fluxes forthe group of stars as a whole, although a good correlation is presentfor a subgroup, i.e., the dMe/dKe's. The Mg II and X-ray luminositiesfor these active stars define an upper boundary, which is dependent uponthe stellar radii. The Mg II luminosity from the less active dM/dK starsare also radii-dependent, but this is not the case for the X-rayluminosity. This may indicate a difference in the heating mechanisms forthe chromosphere and corona, with acoustic wave heating being animportant contributor in the chromosphere and/or a difference in theplage filling factors in the two regions.
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UBV (RI)c photometry of faint nearby stars.
Not Available
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Merged log of IUE observations.
Not Available
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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.
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A photometric study of six nearby common-proper-motion pairs
Six nearby common-proper-motion pairs are studied with new photometry.The constituents are found to be approximately one-half normal dwarfsand one-half subdwarfs, with an 'ultrasubdwarf' (3.8 mag under-luminous)and a degenerate star in the sample as well.
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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.
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Catalogue of stars with CaII H and K emissions
Not Available
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Spectral Types of M Dwarf Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJS...28....1J&db_key=AST
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The luminosity law for late-type main-sequence stars in the solar neighborhood
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974PASP...86..697E&db_key=AST
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Photoelectric UBV observations made on the Palomar 20-inch telescope
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973MNRAS.164..133P&db_key=AST
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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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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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Calcium emission intensities as indicators of stellar age.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970MNRAS.148..463W&db_key=AST
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Radial velocities of dK and dM stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967AJ.....72..905W&db_key=AST
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The radial velocities of 166 red dwarf stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954AJ.....59..218D&db_key=AST
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Dwarf M. Stars Found Spectrophotometrically-Third List.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1952ApJ...116..117V&db_key=AST
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INHABITED SKY
