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HD 170809


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Astrometric and astrophysical discontinuities between the galactic old disk and halo stellar populations
Intermediate band, RI, and DDO photometry of the weak-lined stars in thefirst three volumes of the Michigan catalogs of spectral type arediscussed on the basis of luminosity and heavy element abundance. Theinterface between the old disk (Fe/H greater than -0.8 dex) and halo(Fe/H less than -1.2 dex) populations represents discontinuities in boththe stellar motions and the stellar physics. The CN strengths of bothevolved and unevolved halo stars decrease with decreasing temperature,in a mirror image of the increase with decreasing temperature for thedisk objects. The result for the halo giants has been attributed to deepmixing in the stellar atmospheres but the similar result for unevolveddwarfs indicates a difference in formation rather than in evolutionaryprocess of the two populations.

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Observation and Astrometry data

Constellation:Ταώς
Right ascension:18h37m34.33s
Declination:-70°30'52.3"
Apparent magnitude:8.472
Distance:1075.269 parsecs
Proper motion RA:4.7
Proper motion Dec:-63.5
B-T magnitude:9.605
V-T magnitude:8.566

Catalogs and designations:
Proper Names   (Edit)
HD 1989HD 170809
TYCHO-2 2000TYC 9295-912-1
USNO-A2.0USNO-A2 0150-18553778
HIPHIP 91317

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