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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



ID: 742488.0, MPI für Astronomie / Publikationen_mpia
Candidate exoplanet host HD 131399A: a nascent Am star
Authors:Przybilla, N.; Aschenbrenner, P.; Buder, S.
Date of Publication (YYYY-MM-DD):2017
Title of Journal:Astronomy and Astrophysics
Volume:604
Start Page:id. L9 (9 pp)
Audience:Not Specified
Abstract / Description:Direct imaging suggests that there is a Jovian exoplanet around the primary A-star in the triple-star system HD 131399. We investigate a high-quality spectrum of the primary component HD 131399A obtained with FEROS on the ESO/MPG 2.2 m telescope, aiming to characterise the star's atmospheric and fundamental parameters, and to determine elemental abundances at high precision and accuracy. The aim is to constrain the chemical composition of the birth cloud of the system and therefore the bulk composition of the putative planet. A hybrid non-local thermal equilibrium (non-LTE) model atmosphere technique is adopted for the quantitative spectral analysis. Comparison with the most recent stellar evolution models yields the fundamental parameters. The atmospheric and fundamental stellar parameters of HD 131399A are constrained to Teff = 9200 ± 100 K, log g = 4.37 ± 0.10, , , and log L/L = 1.17 ± 0.07, locating the star on the zero-age main sequence. Non-LTE effects on the derived metal abundances are often smaller than 0.1 dex, but can reach up to 0.8 dex for individual lines. The observed lighter elements up to calcium are overall consistent with present-day cosmic abundances, with a C/O ratio of 0.45 ± 0.07 by number, while the heavier elements show mild overabundances. We conclude that the birth cloud of the system had a standard chemical composition, but we witness the onset of the Am phenomenon in the slowly rotating star. We furthermore show that non-LTE analyses have the potential to solve the remaining discrepancies between observed abundances and predictions by diffusion models for Am stars. Moreover, the present case allows mass loss, not turbulent mixing, to be identified as the main transport process competing with diffusion in very young Am stars.
Free Keywords:stars: abundances; stars: atmospheres; stars: chemically peculiar; stars: early-type; stars: fundamental parameters; stars: individual: HD131399
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-6361
URL:http://cdsads.u-strasbg.fr/abs/2017A%26A...604L......
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