Browsing by Subject "spectroscopic binaries"
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Item HR 8257: A Three-Dimensional Orbit And Basic Properties(2009-04) Fekel, Francis C.; Boden, Andrew F.; Tomkin, Jocelyn; Torres, Guillermo; Tomkin, JocelynWe 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.Item KOI-54: The Kepler Discovery of Tidally Excited Pulsations and Brightenings in a Highly Eccentric Binary(2011-11) Welsh, William F.; Orosz, Jerome A.; Aerts, Conny; Brown, Timothy M.; Brugamyer, Erik; Cochran, William D.; Gilliland, Ronald L.; Guzik, Joyce Ann; Kurtz, D. W.; Latham, David W.; Marcy, Geoffrey W.; Quinn, Samuel N.; Zima, Wolfgang; Allen, Christopher; Batalha, Natalie M.; Bryson, Steve; Buchhave, Lars A.; Caldwell, Douglas A.; Gautier, Thomas N., III; Howell, Steve B.; Kinemuchi, K.; Ibrahim, Khadeejah A.; Isaacson, Howard; Jenkins, Jon M.; Prsa, Andrej; Still, Martin; Street, Rachel; Wohler, Bill; Koch, David G.; Borucki, William J.; Cochran, William D.Kepler observations of the star HD 187091 (KIC 8112039, hereafter KOI-54) revealed a remarkable light curve exhibiting sharp periodic brightening events every 41.8 days with a superimposed set of oscillations forming a beating pattern in phase with the brightenings. Spectroscopic observations revealed that this is a binary star with a highly eccentric orbit, e = 0.83. We are able to match the Kepler light curve and radial velocities with a nearly face-on (i = 5 degrees.5) binary star model in which the brightening events are caused by tidal distortion and irradiation of nearly identical A stars during their close periastron passage. The two dominant oscillations in the light curve, responsible for the beating pattern, have frequencies that are the 91st and 90th harmonic of the orbital frequency. The power spectrum of the light curve, after removing the binary star brightening component, reveals a large number of pulsations, 30 of which have a signal-to-noise ratio greater than or similar to 7. Nearly all of these pulsations have frequencies that are either integer multiples of the orbital frequency or are tidally split multiples of the orbital frequency. This pattern of frequencies unambiguously establishes the pulsations as resonances between the dynamic tides at periastron and the free oscillation modes of one or both of the stars. KOI-54 is only the fourth star to show such a phenomenon and is by far the richest in terms of excited modes.Item New Observational Constraints On The Nu Andromedae System With Data From The Hubble Space Telescope And Hobby-Eberly Telescope(2010-06) McArthur, Barbara E.; Benedict, G. Fritz; Barnes, Rory; Martioli, Elder; Korzennik, Sylvain; Nelan, Ed; Butler, R. Paul; McArthur, Barbara E.; Benedict, G. Fritz; Martioli, ElderWe have used high-cadence radial velocity (RV) measurements from the Hobby-Eberly Telescope with existing velocities from the Lick, Elodie, Harlan J. Smith, and Whipple 60 '' telescopes combined with astrometric data from the Hubble Space Telescope Fine Guidance Sensors to refine the orbital parameters and determine the orbital inclinations and position angles of the ascending node of components v And A c and d. With these inclinations and using M(*) = 1.31M(circle dot) as a primary mass, we determine the actual masses of two of the companions: And A c is 13.98+ 2.3 -5.3 MJUP, and. And A d is 10.25(-3.3)(+0.7) M(JUP). These measurements represent the first astrometric determination of mutual inclination between objects in an extrasolar planetary system, which we find to be 29 degrees.9 +/- 1 degrees. The combined RV measurements also reveal a long-period trend indicating a fourth planet in the system. We investigate the dynamic stability of this system and analyze regions of stability, which suggest a probable mass of v And A b. Finally, our parallaxes confirm that v And B is a stellar companion of v And A.