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Speckle Interferometry of Southern Double Stars. II. Measures from the CASLEO 2.15 Meter Telescope, 1995-1996
Relative astrometry is presented for 198 observations of 160 doublestars. The data were obtained at the 2.15 m telescope at the ComplejoAstronómico El Leoncito (Argentina) with a multianodemicrochannel array (MAMA) detector system. Five high-qualitynondetections are also reported. When judged against ephemeris positionsfor binaries with very well determined orbits, the separation residualsexhibit a root mean square deviation of13.2+3.4-1.9 mas and the position angle residualsexhibit rms deviation of 2.9d+0.8d-0.5d. Factorsaffecting the measurement precision are discussed.
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| Lithium in population I subgiants
We present a lithium survey for a sample of 91 Pop. I stars. JHKLphotometry was also obtained for 61 stars in the sample. Besides Liabundances, [Fe/H] values were derived. Thanks to Hipparcos parallaxes,we could infer absolute V magnitudes for our sample stars and were ableto place them on the color-magnitude diagram, which allowed us toconstrain their evolutionary status. Masses and ages were derived formost of the stars by comparison with evolutionary tracks. The sample wasoriginally selected so to include class IV stars later thanspectral-type F0, but, based on the location on the color-magnitudediagram, we found a posteriori that a fraction of the stars (about 20%)are either main sequence stars or evolved giants. As it is the case fordwarfs and giants, a large spread in lithium abundance is present amongthe subgiants in our sample. As expected, the average lithium decreasesas the stars evolve along the subgiant branch; however, there is not aone-to-one relationship between the position on the color-magnitudediagram and lithium abundance, and the observed dispersion is onlypartially explainable as due to a dispersion in mass, metallicity, andage. In particular, a dispersion in lithium is seen among slightlyevolved subgiants with masses close to solar but in the sameevolutionary stage as the G2 IV star beta Hyi. The comparison of thebeta Hyi-like sample with a sample of non evolved solar-like starsindeed suggests that beta Hyi has most likely evolved from a mainsequence Li-rich star, rather than from a Li-poor star (like the Sun)that has dredged-up previously stored lithium. Our sample includesseveral stars that have completed the first-dredge up lithium dilution,but that have not yet evolved to the evolutionary point whereextra-mixing in the giant phase is thought to occur. A large number ofthem have Li abundances considerably below the theoretical predictionsof first dredge-up dilution. We confirm that this is due to the factthat the progenitors of these stars are most likely stars that havedepleted lithium while on the main sequence; the fraction of post-dredgeup Li rich/poor stars, in fact, is consistent with the observeddistribution of Li abundances among stars that have just left the mainsequence. The signature of the second mixing (or RGB extra-mixing)episode is evident in the log n(Li) vs. B-V and log n(Li) vs. M_boldistributions of the stars in the sample; it seems however that theextra-mixing occurs at luminosities lower than predicted by the modelsof Charbonnel (1994). Finally, a few evolved giants are found thatshould have passed the second mixing episode, but that do not show signsof it. At least half of them are spectroscopic binaries. Based onobservations carried out at the European Southern Observatory, La Silla,Chile
| ICCD Speckle Observations of Binary Stars. XIII. Measurements During 1989- 1994 From the Cerro Tololo 4 M Telescope
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111..936H&db_key=AST
| 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
| ICCD speckle observations of binary stars. VIII - Measurements during 1989-1991 from the Cerro Tololo 4 M telescope
One-thousand eighty-eight observations of 947 binary star systems,observed by means of speckle interferometry with the 4 m telescope onCerro Tololo, are presented. These measurements, made during the period1989-1991, comprise the second installment of results stemming from theexpansion of our speckle program to the southern hemisphere.
| Micrometric measurements of visual binaries (5th list)
The data resulting from 596 micrometric measurements of 152 binaries areset forth which represent observations taken on the GPO astrograph(described by Scardia, 1990). The traditional declination method is usedto track star position, and some of the measurements are related toprevious work by the author (1990). The data given include O-Cmeasurements corresponding to the Worley and Heintz catalogue (1984) andother relevant data.
| Observations of double stars and new pairs. XIV
Results of a continuing survey of visual double stars are presented,including 4880 measurements made from February 1987 to November 1989.The positions in WDS format and Durchmusterung numbers are given for 194pairs first reported here. Micrometer measurements of 1142 doubles madewith the Swarthmore 61 cm refractor are presented. Magnitudes areestimated for some of the objects. Plate measurements, plateorientations, position angles, number of nights, and measured exposuresare given. Visual observations of 342 pairs obtained in May 1989 atCerro Tololo, mostly with the 1.0 m reflector, are reported.
| The nature of the Yale Common Proper Motion groups of stars
Attention is given to a large group of approximately 90 stars, twogroups of 20-30 stars, and 12 groups of a few stars each, taken from DDOsystem image tube spectral classification and intermediate bandphotometry for the Yale Common Proper Motion groups of 180 southernstars. Spectroscopic and photometric analyses of these groups haveindicated a very scattered Pop I main sequence in their color-magnitudediagrams. Distance moduli of 5 or less were derived from the averagespectroscopic parallaxes, in keeping with the proper motion amplitude of0.1 arcsec/year. The main sequence of each group shows scatter whenplotted in an HR diagram, indicating that they are probably nothomogeneous groups of stars sharing common physical origins.
| Micrometric measurements of southern double stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983A&AS...53..177A&db_key=AST
| Visual double stars measured at Las Campanas Observatory, Chile.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977PASP...89..582H&db_key=AST
| Micrometer measures of 401 double stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..878W&db_key=AST
| H_alpha Photometry of Late-type Stars. II. F and G Type Dwarf Stars South of the Equator
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966MNRAS.131..467P&db_key=AST
| Fundamental data for southern stars (First list)
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1957MNRAS.117..534E&db_key=AST
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