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Analysis of the Dynamic Stability of Selected Multiple Stars with Weak Hierarchy
The stability of multiple systems with known orbital elements and withsubsystems occupying adjacent hierarchy levels is analyzed using sixstability criteria and numerical simulations of their dynamicalevolution. All the stability criteria considered are in qualitativeagreement with the numerical computations. Of the 16 systems studied, 11are confirmed to be stable and five (HD 40887, HD 136176, HD 150680, HD217675, and HD 222326) may be unstable on time scales of ˜106 yr orless. The small dynamical ages of the unstable systems may indicate thatthey have captured components during encounters between close binariesand field or moving cluster stars. The instability could also resultfrom the perturbation of a stable system when it approaches a massiveobject (star, black hole, or molecular cloud). It is possible that someof the unstable systems are remnants of small clusters or stellargroups.

Rotation and differential rotation in field F- and G-type stars
We present a detailed study of rotation and differential rotationanalyzing high resolution high S/N spectra of 142 F-, G- and earlyK-type field stars. Using Least Squares Deconvolution we obtainbroadening profiles for our sample stars and use the Fourier transformmethod to determine projected rotational velocities v sin i.Distributions of rotational velocities and periods are studied in theHR-diagram. For a subsample of 32 stars of spectral type F0-G0 we derivethe amount of differential rotation in terms of alpha = (Omega_Equator- Omega_Pole )/Omega_Equator . We find evidence for differentialrotation in ten of the 32 stars. Differential rotation seems to be morecommon in slower rotators, but deviations from rigid rotation are alsofound in some fast rotators. We search for correlations betweendifferential rotation and parameters relevant for stellar activity andshow indications against strong differential rotation in very activestars. We derive values of Delta P and Delta Omega , which support aperiod dependence of differential rotation. Derived lap times 2pi /DeltaOmega are of the order of 20 d and contradict the assumption thatconstant lap times of the order of the solar one ( ~ 130 d) are therule in stars that are thought to harbour magnetic dynamos.Based on observations collected at the European Southern Observatory, LaSilla.Tables 3 and A1 are only available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr ( or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/398/647

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 ( or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521

Direct Observation of the Fourth Star in the ζ Cancri System
Direct imaging of the ζ Cnc system has resolved the fourth star inthe system, which is in orbit around ζ Cnc C. The presence of thefourth star has been inferred for many years from irregularities in themotion of star C and recently from C's spectroscopic orbit. However, itsmass is close to that of C, making its nondetection puzzling. Observingat wavelengths of 1.2, 1.7, and 2.2 μm with the adaptive opticssystem of the Canada-France-Hawaii Telescope, we have obtained imageswhich very clearly reveal star D and show it to have the color of an M2star. Its brightness is consonant with its being two M stars, which arenot resolved in our observations but are likely to be in a short-periodorbit, thereby accounting for the large mass and the difficulty ofdetection at optical wavelengths, where the magnitude difference is muchlarger. The positions and colors of all four stars in the system arereported and are consistent with the most recent astrometricobservations.

Spectroscopic binary orbits from photoelectric radial velocities. Paper 150: zeta Cancri C
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An investigation of the multiple star Zeta Cnc by a lunar occultation
We analyze and discuss a lunar occultation of the multiple starzeta Cnc, obtained in the near-infrared. Thelong-sought D component, recently imaged with the help of adaptiveoptics also by Hutchings et al. (\cite{Hut00}), is clearly seen in theoccultation light curve, and we determine its projected separation andbrightness ratio with high accuracy. Regarding the suggested binarynature of D, we provide an estimate of the upper limit of itsseparation. In addition, we find evidence for a further component in thesystem. The signal from this latter is at the limit of detection, but itis confirmed by three independent data analysis methods. We discuss theastrometry and photometry of the system, and the implications for themass and spectral characteristics of the components. With a projectedseparation of 0farcs064 , the proposed E component could form a closepair with zeta Cnc C. However, at the present stagewe have to consider it only as tentative, and further observations bylarge telescopes or large interferometric facilities will be needed toconfirm and study it in detail. Based on observations collected at TIRGO(Gornergrat, Switzerland), and at Calar Alto (Spain). TIRGO is operatedby CNR-CAISMI Arcetri, Italy. Calar Alto is operated by theGerman-Spanish Astronomical Center.

Inclination of the Orbital Planes of Visual Binaries
The inclination of the orbital planes of 78 visual binaries with knownorbits with respect to the galactic was examined. No double stargroupings were found having approximately equal orientation of theirorbital planes. Viewed the orbital plane north poles there are morebinary systems with counterclockwise motion than those moving clockwise.

The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars
We present X-ray data for all main-sequence and subgiant stars ofspectral types A, F, G, and K and luminosity classes IV and V listed inthe Bright Star Catalogue that have been detected as X-ray sources inthe ROSAT all-sky survey; several stars without luminosity class arealso included. The catalogue contains 980 entries yielding an averagedetection rate of 32 percent. In addition to count rates, sourcedetection parameters, hardness ratios, and X-ray fluxes we also listX-ray luminosities derived from Hipparcos parallaxes. The catalogue isalso available in electronic form via anonymous ftp tocdsarc.u-strasbg.fr ( or viahttp://cdsweb.u-strasbg.fr/Abstract.html

Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.

Optical Polarization of 1000 Stars Within 50-PARSECS from the Sun
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..101..551L&db_key=AST

Some revisions to the Bright Star Catalogue and its supplement
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Absolute quadrant determinations from speckle observations of binary stars
Vector-autocorrelation techniques are highly suited to extractingastrometric information from very large volumes of speckle data in nearreal time, but they inherently introduce a 180-deg ambiguity in theposition-angle measurement. This can be a problem in determining theorbital motions in binaries, so an algorithm is presented whichmaintains most of the simplicity of vector autocorrelation whileremoving the quadrant ambiguity. Results are provided fromabsolute-quadrant determinations for 66 binary star systems firstresolved by the long-term GSU/CHARA speckle program. The algorithm isused to eliminate the period ambiguity in the orbit of the close visualbinary ADS 9744.

A complete sample of wide binaries in the solar neighborhood
A well-defined sample of unambiguously bound wide binaries in the solarneighborhood is presented. The sample appears complete for physicalsystems where s is greater than 0.32 mpc, M(V) is less than 9.0, pi is0.040 arcsec or greater, and delta is larger than -12 deg. The samplecontains 39 systems, of which about 41 percent are hierarchical systems.The distribution of the separations from the sample obeys a simple powerlaw relation. A sharp cutoff in number density is indicated at about 0.1pc. Based on the sample, number densities for wide binaries arecalculated as a function of separation. It appears that about 3 percentof local stars should be members of systems wider than 0.01 pc.

Image sharpening of time-tagged counts from a photon counting detector - Application of a modified Wiener filter
A method for applying a modified Wiener filter to time-tagged singlephoton data is proposed which can preprocess the data for use by a widerange of image sharpening algorithms. The method is applied to data fromthe 50-cm Roque de los Muchachos Observatory telescope, resulting innear diffraction limited images of the bright triple-star system ADS6650with a high dynamic range at extremely low counting rates. The methodcan be used, with a 1.5-m telescope, for fields containing referencestars as faint as 16.75 mag.

Micrometer Measurements of Visual Double Stars - Part Three -
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Photometric Data for the Bright Stars
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Solar colors on the 13-color system
New photometry for an additional 63 solar-like stars is given. Usingthese new data, three independent methods for defining the solar colorson the 13-color system of photometry give unbiased color estimates forthe sun. The independent color determinations are compared to each otherand to previously selected solar analogs. We suggest that the two starsHR 1662 and HR 3309 deserve additional study as possible solar analogs.An improved absolute calibration of relative colors is also derived forthe 13-color system.

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.

Radial Velocities of Binary and Proper-Motion Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981ApJS...46..247H&db_key=AST

Visual multiples. VII - MK classifications
Classifications are given for 865 components of visual multiples; theyshow no systematic differences from the MK system, and the random errorsare one subclass in type and two-thirds of a luminosity class. It isfound that at least 1% of the F-type IV and V stars are weak-lined, 32%of the A4-F1 IV and V stars are Am, and 5% of the A0-A3 IV and V starsare early-type Am. Attention is called to the large fraction (55%) ofthe A3-A9 III-V stars that are of luminosity classes III or IV, unlikethe percentage (16%) at neighboring types.

Erratum - Discordances Between SAO and HD Numbers for Bright Stars
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Visual multiples. IV - Radial velocities of 13 systems
120 radial velocities are given from spectra obtained with the LickObservatory Mills spectrograph for 13 visual systems with periods of 2.6to 26.4 years. The various identifications, the 1900 coordinates, theheliocentric Julian dates, the corrected radial velocities and theinternal probable errors are tabulated.

Uvby-Beta Photometry of Equatorial and Southern Bright Stars - Part Two
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...42..311H&db_key=AST

Photometric differences of magnitude in southern double stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....84..108F&db_key=AST

Speckle interferometric measurements of binary stars. III.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979ApJ...228..493M&db_key=AST

The close approaches of the minor planet Eunomia to the stars SAO 97745, 97645, and 97646
The accuracy of predictions of occultations of minor planets has beenchecked. Eunomia showed close approaches to the stars SAO 97745, 97645,and 97646 as photographed from Observatoire de Haute Provence.Observations of this kind could improve the planetary theories and,eventually, lead to reliable asteroid diameters.

Double star measures at Lick Observatory, Mount Hamilton, California.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978PASP...90..465H&db_key=AST

Binary stars unresolved by speckle interferometry
The epochs of 372 speckle observations obtained with the 4-m Mayalltelescope at KPNO during 1975-77 are given for 156 unresolved visual,astrometric, spectrum, occultation, and spectroscopic binary stars.Specified thresholds are set for detectible angular separations andmagnitude differences so that the negative observations presented herecan be used to place constraints on orbital parameters.

Speckle interferometric measurements of binary stars. II
Results are presented for 219 observations of 155 binary systemsperformed by means of speckle interferometry. The measured separationsrange from 0.033 to 3.25 arcsec with a mean of 0.38 arcsec and 65observations of separation less than 0.12 arcsec. Directly resolvedsystems include HR 1129, HR 2304, 53 Aur, Beta Sco CE, HR 6697, 17 Sgr,74 Aqr, Omicron And, 94 Aqr Aa, and Psi And. Further observations arereported for the 'speckle binaries' 12 Per, 51 Tau, Eta Ori, 19 Leo, EtaVir Aa, Theta Vir, Beta CrB, Delta Sco, Sigma Her, Chi Dra, Delta Sge,Beta Cep Aa, and Xi Cep Aa, as well as for the interferometric binariesAlpha Aur and Alpha Del Aa. Orbit residuals are determined fromavailable orbits and used to check for systematic errors; it isconcluded that there are no serious systematic errors present in theobservations reported.

Photographic measures of double stars. II
Measures are presented for 302 double stars photographed on 657 plateswith the 36-in. Lick refractor in the period between 1945 and 1962. Thedata provided include the observing epochs, the rectangular coordinatesof the secondary components with reference to the respective primaries,the mean errors of a single measurement, the computed mean errors, thedouble-star separations, and the position angles both for the observingepoch and reduced to the equator of 2000. An additional 561 unmeasuredplates of acceptable quality obtained between 1948 and 1960 are listed.

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Observation and Astrometry data

Right ascension:08h12m13.30s
Apparent magnitude:6.2
Distance:25.569 parsecs

Catalogs and designations:
Proper Names   (Edit)
Bayerζβ Cnc
Flamsteed16 Cnc
HD 1989HD 68255
BSC 1991HR 3210

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