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Multiplicity among Widely Separated Brown Dwarf Companions to Nearby Stars: Gliese 337CD
We present Lick Natural Guide Star Adaptive Optics observations of theL8 brown dwarf Gl 337C, which is resolved for the first time into twoclosely separated (0.53"+/-0.03"), nearly equal magnitude componentswith a Ks flux ratio of 0.93+/-0.10. Companionship isinferred from the absence of a 3.6" offset source in Two Micron All SkySurvey or photographic plate images, implying that the observedsecondary component is a comoving late-type dwarf. With a projectedseparation of 11 AU and nearly equal magnitude components, Gl 337CD hasproperties similar to those of other known companion and fieldsubstellar binaries. Its long orbital period (estimated to be ~140-180yr) inhibits short-term astrometric mass measurements, but the Gl 337CDsystem is ideal for studying the L-T transition at a fixed age andmetallicity. From a compilation of all known widely separated (>~100AU) stellar-brown dwarf multiple systems, we find evidence that thebinary fraction of brown dwarfs in these systems is notably higher thanthat of field brown dwarfs, 45+15-13% versus18+7-4% for analogous samples. We speculate onpossible reasons for this difference, including the possibility thatdynamic (ejection) interactions that may form such wide pairspreferentially retain binary secondaries because of their greatercombined mass and/or ability to absorb angular momentum.
| Speckle Interferometry at the US Naval Observatory. V.
The results of 1544 speckle interferometric observations of 637 binarystars, ranging in separation from 0.25" to 5.25", are tabulated. Theseobservations were obtained using the 66 cm refractor at the US NavalObservatory in Washington, DC, with an intensified CCD detector. This isthe fifth in a series of papers presenting measures obtained with thissystem and covers the period 1998 January 1 through December 31. Randomerrors for all measures are estimated to be 17.6 mas in separation and0.55d/ρ in position angle, where ρ is the separation inarcseconds.
| Speckle Interferometry at the US Naval Observatory. IV.
The results of 1314 speckle interferometric observations of 625 binarystars, ranging in separation from 0.2" to 5.2" with a limiting secondarymagnitude of V=11, are tabulated. These observations were obtained usingthe 66 cm refractor at the US Naval Observatory in Washington, DC, withan intensified CCD detector. This is the fourth in a series of paperspresenting measures obtained with this equipment and covers the period1997 January 1 through December 31. Random errors for all measures areestimated to be 18 mas in separation and 0.57d/rho in position angle,where rho is the separation in arcseconds.
| 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.
| UBV absolute CCD photometry and differential astrometry of a sample of visual double stars with A-type primaries
We present V magnitudes, (B-V) and (U-B) colours of the components of111 visual double stars and their relative position measurements rho andtheta . The primaries are of spectral class A; the angular separation isin the 2farcs5 -8arcsec range. The observations were made at the 61-cmreflector of University of Toronto Southern Observatory, Chile. Theobtained photometric results are of a moderate quality for absolutevalues (0.04() m (mag) in V and about 0.02() m in the (B-V) and (U-B)colour indices) and more precise in Delta V and Delta (U-B), Delta (B-V)(0.023() m and 0.015() m, respectively). We find that about 60% ofsecondaries are also of spectral type A; 56% of pairs have Delta (B-V)less than 0.1() m. The two-colour diagram reveals significant offset ofobjects from the curve of unreddened Main Sequence stars. Acomprehensive survey of stars in the close vicinity to the objects isalso presented. The final astrometric accuracy of ~ 0farcs01 in rho and0fdg1 in theta provides additional measurements for study of relativemotion of the components. Based on observations made at University ofToronto Southern Observatory, Las Campanas, Chile. Tables\arabic{tabptm}--\arabic{tabast} are only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/Abstract.html
| A preliminary compilation of DS-programme star positions
A catalog is presented of the double-star-program (DS-program) starpositions, listing right ascensions for 930 DSs and declinations for1225 DSs of the program. The positions were compiled from the observedvalues obtained between 1980 and 1987 with the meridian circles of sixUSSR observatories (the Moscow, Kazan', Kiev, Khar'kov, Odessa, andTashkent Observatories) and the Belgrade Observatory. The measurementsand the treatment of the observational material were performed using therelative method, and the FK-4 system stars were used as reference stars.
| Catalog of Indidual Radial Velocities, 0h-12h, Measured by Astronomers of the Mount Wilson Observatory
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...19..387A&db_key=AST
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