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A Precise Orbit Determination of χ1 Orionis from Astrometric and Radial Velocity Data
We have derived an accurate orbit of χ1 Orionis (HD39587, HIP 27913, HR 2047) by combining precise astrometric and radialvelocity data. The combined orbital analysis yields P=5156.7+/-2.5 days,K1=1.885+/-0.004 km s-1,α1=94.8+/-1.6 mas, e=0.451+/-0.003, and mass ratio(M2/M1) q=0.15+/-0.005. The mass ratio derivedhere is among the smallest well-determined ratio for a G-type dwarfprimary star. We have also obtained a parallax of χ1Orionis, 115.93+/-1.02 mas, in excellent agreement with the Hipparcosvalue.
| On the variability of BD +20 1171.
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| Spectroscopic parallaxes of MAP region stars from UBVRI, DDO, and uvbyH-beta photometry
This paper presents the results of spectral type and luminosityclassification of reference stars in the Allegheny Observatory MAPparallax program, using broadband and intermediate-band photometry. Inaddition to the use of UBVRI and DDO photometric systems, the uvbyH-betaphotometric system was included for classification of blue (B - V lessthan 0.6) reference stars. The stellar classifications made from thephotometry are used to determine spectroscopic parallaxes. Thespectroscopic parallaxes are used in turn to adjust the relativeparallaxes measured with the MAP to absolute parallaxes. A new methodfor dereddening stars using more than one photometric system ispresented. In the process of dereddening, visual extinctions, spectraltypes, and luminosity classes are determined, as well as a measure ofthe goodness of fit. The measure of goodness of fit quantifiesconfidence in the stellar classifications. It is found that the spectraltypes are reliable to within 2.5 spectral subclasses.
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