Examinando por Autor "Weinberger, A."

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    MagAO IMAGING OF LONG-PERIOD OBJECTS (MILO). I. A BENCHMARK M DWARF COMPANION EXCITING A MASSIVE PLANET AROUND THE SUN-LIKE STAR HD 7449
    (IOP PUBLISHING, 2016-02) Rodigas, T.J.; Arriagada, P.; Faherty, J.; Anglada-Escudé, G.; Kaib, N.; Butler, R.P.; Shectman, S.; Weinberger, A.; Males, J.R.; Morzinski, K.M.; Close, L.M.; Hinz, P.M.; Crane, J.D.; Thompson, I.; Teske, J.; Diaz, M.; Minniti, D.; Lopez-Morales, M.; Adams, F.C.; Boss, A.P.
    We present high-contrast Magellan adaptive optics images of HD 7449, a Sun-like star with one planet and a long-term radial velocity (RV) trend. We unambiguously detect the source of the long-term trend from 0.6-2.15 mu m. at a separation of similar to 0.'' 54. We use the object's colors and spectral energy distribution to show that it is most likely an M4-M5 dwarf (mass similar to 0.1-0.2 M-circle dot) at the same distance as the primary and is therefore likely bound. We also present new RVs measured with the Magellan/MIKE and Planet Finder Spectrograph spectrometers and compile these with archival data from CORALIE and HARPS. We use a new Markov chain Monte Carlo procedure to constrain both the mass (>0.17 M-circle dot at 99% confidence) and semimajor axis (similar to 18 AU) of the M dwarf companion (HD 7449B). We also refine the parameters of the known massive planet (HD 7449Ab), finding that its minimum mass is 1.09(-0.19)(+0.52) M-J, its semimajor axis is 2.33(-0.02)(+0.01) AU, and its eccentricity is 0.8(-0.06)(+0.08). We use N-body simulations to constrain the eccentricity of HD 7449B to less than or similar to 0.5. The M dwarf may be inducing Kozai oscillations on the planet, explaining its high eccentricity. If this is the case and its orbit was initially circular, the mass of the planet would need to be less than or similar to 1.5 M-J. This demonstrates that strong constraints on known planets can be made using direct observations of otherwise undetectable long-period companions.
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    MagAO IMAGING OF LONG-PERIOD OBJECTS (MILO). II. A PUZZLING WHITE DWARF AROUND THE SUN-LIKE STAR HD 11112
    (IOP PUBLISHING, 2016-11) Rodigas, T.J.; Bergeron, P.; Simon, A.; Arriagada, P.; Faherty, J.K.; Anglada-Escudé, G.; Mamajek, E.E.; Weinberger, A.; Butler, R.P.; Males, J.R.; Morzinski, K.; Close, L.M.; Hinz, P.M.; Bailey, J.; Carter, B.; Jenkins, J.S.; Jones, H.; O'Toole, S.; Tinney, C.G.; Wittenmyer, R.; Debes, J.
    HD 11112 is an old, Sun-like star that has a long-term radial velocity (RV) trend indicative of a massive companion on a wide orbit. Here we present direct images of the source responsible for the trend using the Magellan Adaptive Optics system. We detect the object (HD 11112B) at a separation of 2 2 (100 au) at multiple wavelengths spanning 0.6-4 mu m. and show that it is most likely a gravitationally bound cool white dwarf. Modeling its spectral energy distribution suggests that its mass is 0.9-1.1M(circle dot), which corresponds to very high eccentricity, near edge-on orbits from a. Markov chain Monte Carlo analysis of the RV and imaging data together. The total age of the white dwarf is > 2 sigma, which is discrepant with that of the primary star under most assumptions. The problem can be resolved if the white dwarf progenitor was initially a double white dwarf binary that then merged into the observed high-mass white dwarf. HD 11112B is a unique and intriguing benchmark object that can be used to calibrate atmospheric and evolutionary models of cool white dwarfs and should thus continue to be monitored by RV and direct imaging over the coming years.