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HD 21940


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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).

Secondary standards for H-beta photometry in the Southern Hemisphere (second series).
Not Available

UBV (RI)c standard stars in the E- and F-regions and in the Magellanic Clouds - a revised catalogue.
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UBV(RI)c photometry of some standard sequences in the Harvard F regions and in the Magellanic Clouds
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1988MNRAS.231.1047M&db_key=AST

DDO Observations of Southern Stars
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Standard Stars for VRI Photometry with S25 Response Photocathodes
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Further observations of magnitude with a coarse grating
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1952MNRAS.112..665W&db_key=AST

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Observation and Astrometry data

Constellation:Hydre mâle
Right ascension:03h24m36.88s
Declination:-76°44'46.6"
Apparent magnitude:6.801
Distance:94.162 parsecs
Proper motion RA:-42.1
Proper motion Dec:-67.9
B-T magnitude:7.05
V-T magnitude:6.822

Catalogs and designations:
Proper Names   (Edit)
HD 1989HD 21940
TYCHO-2 2000TYC 9363-826-1
USNO-A2.0USNO-A2 0075-00565633
HIPHIP 15886

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