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Stellar and Planetary Characterization of the Ross 128 Exoplanetary System from APOGEE Spectra

Souto, Diogo; Unterborn, Cayman T.; Smith, Verne V.; Cunha, Katia; Teske, Johanna; Covey, Kevin; Rojas-Ayala, Bárbara; García-Hernández, D. A.; Stassun, Keivan and Zamora, Olga, et al. (2018) In Astrophysical Journal Letters 860(1).
Abstract

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... (More)

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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published
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keywords
infrared: stars, planetary systems, planetstar interactions, stars: abundances, stars: fundamental parameters, stars: low-mass
in
Astrophysical Journal Letters
volume
860
issue
1
publisher
University of Chicago Press
external identifiers
  • scopus:85049052764
ISSN
2041-8205
DOI
10.3847/2041-8213/aac896
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English
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yes
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3dd418b8-3c98-43ec-b20d-98f68ee92167
date added to LUP
2018-07-06 12:36:12
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2018-07-06 12:36:12
@article{3dd418b8-3c98-43ec-b20d-98f68ee92167,
  abstract     = {<p>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 <sub>eff</sub> = 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 <sub>Earth</sub> = 1.79 ±0.26) and equilibrium temperature (T <sub>eq</sub> = 294 ±10 K) - support previous findings that Ross 128b is a temperate exoplanet in the inner edge of the habitable zone.</p>},
  articleno    = {L15},
  author       = {Souto, Diogo and Unterborn, Cayman T. and Smith, Verne V. and Cunha, Katia and Teske, Johanna and Covey, Kevin and Rojas-Ayala, Bárbara and García-Hernández, D. A. and Stassun, Keivan and Zamora, Olga and Masseron, Thomas and Johnson, J. A. and Majewski, Steven R. and Jönsson, Henrik and Gilhool, Steven and Blake, Cullen and Santana, Felipe},
  issn         = {2041-8205},
  keyword      = {infrared: stars,planetary systems,planetstar interactions,stars: abundances,stars: fundamental parameters,stars: low-mass},
  language     = {eng},
  month        = {06},
  number       = {1},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal Letters},
  title        = {Stellar and Planetary Characterization of the Ross 128 Exoplanetary System from APOGEE Spectra},
  url          = {http://dx.doi.org/10.3847/2041-8213/aac896},
  volume       = {860},
  year         = {2018},
}