Bibcode
Souto, D.; Unterborn, Cayman T.; Smith, Verne V.; Cunha, Katia; Teske, Johanna; Covey, Kevin; Rojas-Ayala, Bárbara; García-Hernández, D. A.; Stassun, Keivan; Zamora, O.; Masseron, T.; Johnson, J. A.; Majewski, Steven R.; Jönsson, Henrik; Gilhool, Steven; Blake, Cullen; Santana, Felipe
Bibliographical reference
The Astrophysical Journal Letters, Volume 860, Issue 1, article id. L15, 7 pp. (2018).
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6
2018
Citations
30
Refereed citations
29
Description
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.
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