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An Astrometric Study of Procyon
We report on the analysis of observations of Procyon obtained with theMultichannel Astrometric Photometer during the years 1986-2004. Whilethe results significantly increase the precision of the estimatedcharacteristics of the components of the system, they are generally ingood agreement with the most recent studies. The F5 IV primary is foundto have a mass of 1.43+/-0.034 Msolar, while the white dwarfcompanion's mass is 0.58+/-0.014 Msolar. The distance modulusis 2.277+/-0.005 mag, yielding an absolute visual magnitude for thecombined light of the system of 2.640+/-0.006 and an absolute visualmagnitude of the secondary of 13.20+/-0.05. The residuals of the fit ofthe positions of the photocenter to the excepted orbit support theparameters of that orbit, showing only a slight deviation in rightascension. The most significant improvements in our knowledge of thebinary system can be made with further measurements of the separation ofthe components. The masses found here tend to reaffirm the recent modelsof the nature of the primary and secondary stars.
| Speckle Interferometry at the US Naval Observatory. II.
Position angles and separations resulting from 2406 speckleinterferometric observations of 547 binary stars are tabulated. This isthe second in a series of papers presenting measures obtained using the66 cm refractor at the US Naval Observatory in Washington, DC, with anintensified CCD detector. Program stars range in separation from 0.2" to3.8", with Deltam<=2.5 mag and a limiting magnitude of V=10.0. Theobservation epochs run from 1993 January through 1995 August. Randomerrors are estimated to be 14 mas in separation and 0.52d/rho inposition angle, where rho is the separation in arcseconds. Theinstrumentation and calibration are briefly described. Aspects of thedata analysis related to the avoidance of systematic errors are alsodiscussed.
| Photometry of astrometric reference stars
UBVRI, DDO, and uvby, H-beta photometry of astrometric reference starsis presented. Spectral types and luminosity classifications made fromthe colors are used to determine their spectroscopic parallaxes. In thispaper, colors for 309 stars in 25 regions are given, and classificationsfor 210 stars have been made. These stars form reference frames in theAllegheny Observatory Multichannel Astrometric Photometer astrometricprogram, and in the Praesepe cluster reduced by Russell (1976). It isfound that the present photometric spectral types are reliable to within2.5 spectral subclasses.
| 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.
| The Orbit and Parallax of Procyon.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1951ApJ...113....1S&db_key=AST
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