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Photometric Elements, Apsidal Motion, and a Third Body in the Eclipsing Binary HP Aur
Highly accurate W BV R photometric measurements of the eclipsing binaryHP Aur were performed in 2002 2003 with the 48-cm AZT-14 reflector atthe Tien-Shan High-Altitude Observatory to determine the rate of apsidalmotion. A consistent system of physical and geometrical parameters ofthe components and the binary as a whole has been constructed for thefirst time by analyzing these new measurements together with otherpublished data: we determined their radii (R 1 = 1.05R ȯ, R 2 =0.82R ȯ) and luminosities (L 1 = 1.10L ȯ, L 2 = 0.46L ȯ),spectral types (G2V + G8V) and surface gravities (log g 1 = 4.38, log g2 = 4.51), age (t = 9.5 × 109 yr), and the distance to the binary(d = 197 pc). We detected an ultraviolet excess in the spectra of bothcomponents, &$Delta (W - B) ≃ - 0mathop .limits(m) 25$; , that is probably attributable to a metal deficiency in theatmospheres of these stars. In this system of two solar-type stars, wefound a third body with the mass M 3 sin i 3 3 = 0.17M ȯ thatrevolved with the period P3 = 13.7 yr around the eclipsing binary in ahighly eccentric elliptical orbit: e 3 = 0.70 and A 3 sin i 3 ≃ 7AU. The orbit of the eclipsing binary itself was shown to be alsoelliptical, but with a low eccentricity (e = 0.0025(5)), while apsidalmotion with a period U obs > 80 yr was observed at a theoreticallyexpected period U th ≈ 92 yr. At least 20 to 30 more years ofphotoelectric measurements of this star will be required to reliablydetermine U obs.
| 2000 A UV imaging of a 6 deg diameter field around MU Aurigae
UV imagery of a 6 deg diameter field centered on Mu Aurigae in thegalactic plane was obtained with the SCAP 2000 experiment dedicated toan UV sky survey. Photometric UV magnitudes at 2000 A are given here formore than 500 stars detected in the field. A star-counting method isapplied to give a fine description of the interstellar matterdistribution up to 1000 pc. The mean space density for B8-A3 stars isderived. Stars with an UV excess are detected and spectralreclassification of some single or binary stars is suggested.
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