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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).
| Occultations of stars by asteroids in 1995 and 1996
Predictions, based on a computerized comparison of asteroid ephemerideswith the catalog positions of 567,500 stars, are given for 155occultations of stars by asteroids in 1995 and 1996. On average, thepredictions are expected to be more accurate than in earlier searchesbecause of the use of more modern star catalogs. A number of veryfavorable occultations, visible in North America and elsewhere, arediscussed.
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Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Aslan |
| Sað Açýklýk: | 10h49m01.69s |
| Yükselim: | +20°53'14.1" |
| Görünürdeki Parlaklýk: | 8.696 |
| Uzaklýk: | 55.525 parsek |
| özdevim Sað Açýklýk: | 103.6 |
| özdevim Yükselim: | -104 |
| B-T magnitude: | 9.53 |
| V-T magnitude: | 8.765 |
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