Neon abundances in normal late-B and mercury-manganese stars
We make new non-local thermodynamic equilibrium calculations to deducethe abundances of neon from visible-region echelle spectra of selectedNei lines in seven normal stars and 20HgMn stars. We find that the beststrong blend-free Ne line that can be used at the lower end of theeffective temperature Teff range is λ6402, althoughseveral other potentially useful Nei lines are found in the red regionof the spectra of these stars. The mean neon abundance in the normalstars (logA=8.10) is in excellent agreement with the standard abundanceof neon (8.08). However, in HgMn stars neon is almost universallyunderabundant, ranging from marginal deficits of 0.1-0.3dex tounderabundances of an order of magnitude or more. In many cases, thelines are so weak that only upper limits can be established. The mostextreme example found is υ Her with an underabundance of at least1.5dex. These underabundances are qualitatively expected from radiativeacceleration calculations, which show that Ne has a very small radiativeacceleration in the photosphere, and that it is expected to undergogravitational settling if the mixing processes are sufficiently weak andthere is no strong stellar wind. According to theoretical predictions,the low Ne abundances place an important constraint on the intensity ofsuch stellar winds, which must be less than10-14Msolaryr-1 if they arenon-turbulent.
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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.
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Speckle Interferometry at the US Naval Observatory. III.
Position angles and separations resulting from 2578 speckleinterferometric observations of 590 binary stars are tabulated. This isthe third in a series of papers presenting measures obtained using the66 cm refractor at the US Naval Observatory in Washington, DC, andcovers the period from 1995 June through 1996 December. Program starsrange in separation from 0.2" to 4.3", with a limiting magnitude ofV=11. Random errors are estimated to be 17.0 mas in separation and0.56d/rho in position angle, where rho is the separation in arcseconds.These are the first results acquired using an improved intensified CCDdetector. The new detector, in concert with an intensity-filteringtechnique applied in software, has permitted a 1 mag increase in dynamicrange, to 3.5 mag, for pairs separated by about 2". The instrumentationand calibration are briefly described, with an emphasis on thecharacteristics of the new detector. The software filter used toincrease the dynamic range is also described.
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Micrometer Measures of Double Stars
Micrometer measures of 795 double stars made with the 26 inch (0.66 m)refractor of the US Naval Observatory from 1984 to 1990 are presented.
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Observations of Double Stars. XVIII.
Micrometer observations of 1350 pairs in 1995-1997 are listed.
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Speckle Interferometry at the US Naval Observatory. I.
We present speckle interferometer measurements of 467 binary stars takenat the US Naval Observatory in Washington, DC, using the 66 cmrefractor, from 1990 October through 1992 December. The observingprogram is designed to provide high-quality observations of binaries inthe 0."3--3."5 range of separations and as faint as 10.0 mag. More than8000 measurements have been made to date, of which we report the resultsfor 2329. Not only is it our intent to provide accurate data forinteresting binary stars, but also, by careful calibration, to firmlyrelate the "classical" astrometry of binary stars to that being obtainedtoday by speckle and that which will soon be obtained by other moderntechniques such as long-baseline optical interferometry.
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Visual double stars measured at Lick Observatory Mount Hamilton, California.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979PASP...91..479H&db_key=AST
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Mesures d'etoiles doubles faites AU refracteur de 38cm de l'Observatoire de Nice.
Not Available
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Micrometer measures of doubles stars. III.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963AJ.....68...57V&db_key=AST
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Mesures d'étoiles doubles faites au rĝfraceur de 38 cm de l'Observatoire de Nice
Not Available
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Measures of 241 double stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1960AJ.....65..156W&db_key=AST
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Mesures d'étoiles doubles faites à l'Observatoire de Paris
Not Available
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Measures of double stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61..162W&db_key=AST
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Measures d'étoiles doubles effectuées au Pic du Midi
Not Available
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Mesures d'étoiles doubles effectuées au réfracteur de 38 cm de l' Observatoire de Nice
Not Available
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INHABITED SKY
