http://arxiv.org/abs/1805.11633
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 \micron) high-resolution ($R$$\sim$22,500) spectra from the SDSS-APOGEE survey. We determined precise atmospheric parameters $T_{\rm eff}$=3231$\pm$100K, log$g$=4.96$\pm$0.11 dex and chemical abundances of eight elements (C, O, Mg, Al, K, Ca, Ti, and Fe), finding Ross 128 to have near solar metallicity ([Fe/H] = +0.03$\pm$0.09 dex). The derived results were obtained via spectral synthesis (1-D LTE) adopting both MARCS and PHOENIX model atmospheres; stellar parameters and chemical abundances derived from the different adopted models do not show significant offsets. Mass-radius modeling of Ross 128b indicate that it lies below the pure rock composition curve, suggesting that it contains a mixture of rock and iron, with the relative amounts of each set by the ratio of Fe/Mg. If Ross 128b formed with a sub-solar Si/Mg ratio, and assuming the planet’s composition matches that of the host-star, it likely has a larger core size relative to the Earth. The derived planetary parameters — insolation flux (S${\rm Earth}$=1.79$\pm$0.26) and equilibrium temperature ($T{\rm eq}$=294$\pm$10K) — support previous findings that Ross 128b is a temperate exoplanet in the inner edge of the habitable zone.
D. Souto, C. Unterborn, V. Smith, et. al.
Thu, 31 May 18
9/45
Comments: Accepted in ApJLetters, 3 figures, 2 tables, 12 pages
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