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HD 157008


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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).

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观测天体数据

星座:天燕座
右阿森松:17h34m42.96s
赤纬:-81°04'06.0"
视星:7.698
距离:127.389 天文距离
右阿森松适当运动:6.6
赤纬适当运动:5
B-T magnitude:8.021
V-T magnitude:7.725

目录:
适当名称   (Edit)
HD 1989HD 157008
TYCHO-2 2000TYC 9456-369-1
USNO-A2.0USNO-A2 0075-05839501
HIPHIP 86012

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