HR 8257: A Three-Dimensional Orbit And Basic Properties




Fekel, Francis C.
Boden, Andrew F.
Tomkin, Jocelyn
Torres, Guillermo

Journal Title

Journal ISSN

Volume Title



We have used interferometric and spectroscopic observations of HR 8257 to determine a three-dimensional orbit of the system. The orbit has a period of 12.21345 days and an eccentricity of 0.2895. The masses of the F0 and F2 dwarf components are 1.56 and 1.38M(circle dot), respectively, with fractional errors of 1.4%. Our orbital parallax of 13.632 +/- 0.095 mas, corresponding to a distance of 73.4 +/- 0.6 pc, differs from the Hipparcos result by just 2% and has a significantly smaller uncertainty. From our spectroscopic observations and spectral energy distribution modeling we determine the component effective temperatures and luminosities to be T(eff)(A) = 7030 +/- 200K and T(eff)(B) = 6560 +/- 200K and L(A) = 9.4 +/- 0.3 L(circle dot) and L(B) = 4.7 +/- 0.2 L(circle dot). The primary rotates pseudosynchronously, while the secondary is not far from its pseudosynchronous rotational velocity. Although both early-F stars are slowly rotating, neither component of this close binary is an Am star. A comparison with evolutionary tracks indicates that the stars are slightly metal poor, and although the components have evolved away from the zero-age main sequence, they are both still dwarfs.



LCSH Subject Headings


Fekel, Francis C., Andrew F. Boden, Jocelyn Tomkin, and Guillermo Torres. "HR 8257: a three-dimensional orbit and basic properties." The Astrophysical Journal, Vol. 695, No. 2 (Apr., 2009): 1527.