Examinando por Autor "Stassun, Keivank, I."

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    Stellar and Planetary Characterization of the Ross 128 Exoplanetary System from APOGEE Spectra
    (Institute of Physics Publishing, 2018-06) Souto, Diogo; Unterborn, Cayman T.; Smith, Verne V.; Cunha, Katia; Teske, Johanna; Covey, Kevin; Rojas-Ayala, Bárbara; García-Hernández D.A.; Stassun, Keivank, I.; Zamora, Olga; Masseron, Thomas; Johnson J.A.; Majewski, Steven R.; Jönsson, Henrik; Gilhool, Steven; Blake, Cullen; Santana, Felipe
    The first detailed chemical abundance analysis of the M-dwarf (M4.0) exoplanet-hosting star Ross 128 is presented here, based upon near-infrared (1.5-1.7 μm), high-resolution (R ∼ 22,500) spectra from the SDSS Apache Point Galactic Evolution Experiment survey. We determined precise atmospheric parameters T eff = 3231 ±100 K, log g = 4.96 ±0.11 dex and chemical abundances of eight elements (C, O, Mg, Al, K, Ca, Ti, and Fe), finding Ross 128 to have near solar metallicity ([Fe/H] = +0.03 ± 0.09 dex). The derived results were obtained via spectral synthesis (1D LTE) adopting both MARCS and PHOENIX model atmospheres; stellar parameters and chemical abundances derived from the different adopted models do not show significant offsets. Mass-radius modeling of Ross 128b indicates that it lies below the pure-rock composition curve, suggesting that it contains a mixture of rock and iron, with the relative amounts of each set by the ratio of Fe/Mg. If Ross 128b formed with a subsolar Si abundance, and assuming the planet's composition matches that of the host star, it likely has a larger core size relative to the Earth despite this producing a planet with a Si/Mg abundance ratio ∼34% greater than the Sun. The derived planetary parameters - insolation flux (S Earth = 1.79 ±0.26) and equilibrium temperature (T eq = 294 ±10 K) - support previous findings that Ross 128b is a temperate exoplanet in the inner edge of the habitable zone. © 2018. The American Astronomical Society. All rights reserved.