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Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| UBV photometry of ten southern hemisphere active-chromosphere stars
High-precision UBV photometry of ten southern hemisphereactive-chromosphere stars with strong Ca II H and K and/or H-alphaemission has been obtained. Eight of these stars showed variabilityduring June 1985. Complete or partial light curves are presented for thestars, and these data, as well as mean V magnitudes and colors, arecompared with the results of other investigators. In a number of cases,significant changes in photometric amplitude are found, which may serveto track the formation and evolution of active regions on these stars.
| Visual multiples. VIII - 1000 MK types
A total of 1000 new classifications are given for stars brighter than B= 8.0 mag in the Aitken double star catalog. The classificationssupplement 865 classifications obtained in 1981 and 1984. Among thenewly discovered stars are 12 new Ap stars, eight Lambda Bootis stars,one Ba II star, and 60 Am stars. A detailed list of the newclassifications is given.
| Mitteilungen uber Veranderliche der Bamberger Liste.
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Observation and Astrometry data
| Constellation: | Sagittarius |
| Right ascension: | 18h50m37.51s |
| Declination: | -26°46'13.7" |
| Apparent magnitude: | 7.224 |
| Distance: | 127.226 parsecs |
| Proper motion RA: | 0.3 |
| Proper motion Dec: | -23.7 |
| B-T magnitude: | 7.478 |
| V-T magnitude: | 7.245 |
Catalogs and designations:
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