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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).

Frequency domain analysis of the light changes of the close eclipsing systems TX Ursae Majoris and S CANCRI
The aim of this paper has been to carry out an analysis of the lightcurves of two eclipsing systems TX UMa and S Cnc by Kopal's new methodof the analysis of the light curves of eclipsing systems in thefrequency domain. The elements of these systems are evaluated and theresults are discussed

MK classifications for F-and G-type stars. 3.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79..682H&db_key=AST

Computation of Elements of Eclipsing Binary Stars by High-Speed Computing Machines.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962ApJS....7..351H&db_key=AST

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Dades d'Observació i Astrometria

Constel·lació:Hydra
Ascensió Recta:08h45m23.32s
Declinació:+00°11'51.9"
Magnitud Aparent:6.564
Distancia:110.254 parsecs
Moviment propi RA:-25.9
Moviment propi Dec:-5.9
B-T magnitude:7.842
V-T magnitude:6.67

Catàlegs i designacions:
Noms Propis   (Edit)
HD 1989HD 74686
TYCHO-2 2000TYC 212-933-1
USNO-A2.0USNO-A2 0900-06136802
HIPHIP 42957

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