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Differential photometry of speckle-interferometric binary and multiple stars
A method for differential photometry of speckle-interferometric binaryand multiple stars is presented. Both the accuracy and sources ofsystematic errors of the method are analysed. The photometric accuracyranges between 0.02 m and 0.20 m, depending on the atmospheric seeing,the brightness and the separation of the system components. A comparisonbetween our magnitude differences and those of other authors ispresented.
| The Four-Quadrant Phase Mask Coronagraph. IV. First Light at the Very Large Telescope
We present the first high-contrast images obtained at the ESO Very LargeTelescope using a four-quadrant phase mask coronagraph. The two-nightcommissioning was carried out in 2004 January on NACO, the near-IRcamera with adaptive optics at UT4. We evaluated the behavior of thecoronagraph on a variety of astrophysical targets: binary stars,circumstellar disks, and active galactic nuclei. The performance of thecoronagraph is in agreement with our expectations based on numericalsimulations. The phase mask provides a stellar peak attenuation of afactor of about 10 on average (for long exposure), and its performanceis limited only by the phase residuals (mainly low-order aberrations)that are left uncorrected by the adaptive optics system.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| Speckle Observations of Binary Stars with the WIYN Telescope. IV. Differential Photometry
Five hundred seventy-six magnitude difference measures are presented for260 binary stars. These measures are derived from CCD-based speckleobservations taken at the WIYN 3.5 m telescope at Kitt Peak NationalObservatory during the period 1997-2000. Separations of the systemsrange from over 1" down to near the diffraction limit of the telescope.A study of multiple measures of the same targets indicates that themeasures have a typical uncertainty of better than 0.13 mag per 2 minuteobservation, and that multiple observations can be averaged to arrive atsmaller uncertainties. Results presented here are also compared, insofaras it is possible, with measures in the Hipparcos Catalogue and toprevious studies using adaptive optics. No major systematic errors wereidentified.The WIYN Observatory is a joint facility of the University ofWisconsin-Madison, Indiana University, Yale University, and the NationalOptical Astronomy Observatory.
| Speckle Observations of Binary Stars with the WIYN Telescope. II. Relative Astrometry Measures during 1998-2000
Five hundred twelve relative astrometry measures are presented for 253double stars, including 53 double stars discovered by Hipparcos. In 15cases, relative astrometry is reported for the first time for newlyconfirmed pairs. In addition, 20 high-quality nondetections ofcompanions are reported for stars suspected of being nonsingle byHipparcos. Observations were taken using a fast-readout CCD camerasystem at the WIYN 3.5 m telescope at Kitt Peak, Arizona. In comparingthese measures with ephemeris predictions for binary stars with verywell known orbits, we find that the measurement precision is better than3 mas in separation and 1° in position angle per individualobservation. Measurement precision and detection capabilities are fullydiscussed, and confirmed orbital motion is reported in four cases of theHipparcos double star discoveries. The WIYN Observatory is a jointfacility of the University of Wisconsin-Madison, Indiana University,Yale University, and the National Optical Astronomy Observatory.
| Speckle interferometry of nearby multiple stars
We present the results of diffraction-limited optical speckleinterferometry and infrared bispectrum speckle interferometry of 111double and 10 triple systems performed in 1998-1999 with the 6-mtelescope of the Special Astrophysical Observatory in Zelenchuk. Theobservations concentrated on nearby close binaries discovered during theHipparcos mission. Many nearby fast-orbiting low-mass binaries knownbefore Hipparcos were also included in the program. New companions werefirst resolved in 4 systems: HIP 5245, ADS 3179, Kui 99, and ADS 16138.In addition to accurate relative positions, magnitude differences weremeasured for most of the pairs. We combined our results with theHipparcos parallaxes to derive absolute magnitudes and spectral typesfor 63 binaries and 4 triples. Preliminary orbital elements and themass-sum are derived for HIP 689, and improved orbits are presented forHIP 16602 (CHR 117) and HIP 21280 (CHR 17). Based on data collected atthe Special Astrophysical Observatory, Russia Table 1 is only, and Table2 also, available in electronic form at the CDS via anonymons ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/385/87
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Observation and Astrometry data
| Constellation: | Ωρίων |
| Right ascension: | 05h52m29.42s |
| Declination: | -02°17'07.2" |
| Apparent magnitude: | 7.252 |
| Distance: | 54.348 parsecs |
| Proper motion RA: | -104 |
| Proper motion Dec: | -9.3 |
| B-T magnitude: | 7.901 |
| V-T magnitude: | 7.306 |
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