Spectroscopic and asteroseismic analysis of the remarkable main-sequence A star KIC 11145123
Article
Article Title | Spectroscopic and asteroseismic analysis of the remarkable main-sequence A star KIC 11145123 |
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ERA Journal ID | 1074 |
Article Category | Article |
Authors | Takada-Hidai, Masahide (Author), Kurtz, Donald W. (Author), Shibahashi, Hiromoto (Author), Murphy, Simon J. (Author), Takata, Masao (Author), Saio, Hideyuki (Author) and Sekii, Takashi (Author) |
Journal Title | Monthly Notices of the Royal Astronomical Society |
Journal Citation | 470 (4), pp. 4908-4924 |
Number of Pages | 17 |
Year | 2017 |
Publisher | Oxford University Press |
Place of Publication | United Kingdom |
ISSN | 0035-8711 |
1365-2966 | |
Digital Object Identifier (DOI) | https://doi.org/10.1093/mnras/stx1506 |
Web Address (URL) | https://academic.oup.com/mnras/article/470/4/4908/3869259 |
Abstract | A spectroscopic analysis was carried out to clarify the properties of KIC 11145123 – the first main-sequence star with a directly measured core-to-surface rotation profile – based on spectra observed with the High Dispersion Spectrograph (HDS) of the Subaru telescope. The atmospheric parameters (Teff = 7600 K, log g = 4.2, ξ = 3.1 km s−1 and [Fe/H] = −0.71 dex), the radial and rotation velocities, and elemental abundances were obtained by analysing line strengths and fitting line profiles, which were calculated with a 1D LTE model atmosphere. The main properties of KIC 11145123 are: (1) a low [Fe/H] = −0.71 ± 0.11 dex and a high radial velocity of −135.4 ± 0.2 km s−1. These are remarkable among late-A stars. Our best asteroseismic models with this low [Fe/H] have slightly high helium abundance and low masses of 1.4 M⊙. All of these results strongly suggest that KIC 11145123 is a Population II blue straggler; (2) the projected rotation velocity confirms the asteroseismically predicted slow rotation of the star; (3) comparisons of abundance patterns between KIC 11145123 and Am, Ap, and blue stragglers show that KIC 11145123 is neither an Am star nor an Ap star, but has abundances consistent with a blue straggler. We conclude that the remarkably long 100-d rotation period of this star is a consequence of it being a blue straggler, but both pathways for the formation of blue stragglers – merger and mass loss in a binary system – pose difficulties for our understanding of the exceedingly slow rotation. In particular, we show that there is no evidence of any secondary companion star, and we put stringent limits on the possible mass of any such purported companion through the phase modulation technique. |
Keywords | Stars: abundances; Stars: atmospheres; Stars: individual: KIC 11145123; Stars: oscillations; Stars: rotation; Techniques: spectroscopic; Astrophysics - Solar and Stellar Astrophysics |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
Public Notes | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Byline Affiliations | Tokai University, Japan |
University of Central Lancashire, United Kingdom | |
University of Tokyo, Japan | |
University of Sydney | |
Tohoku University, Japan | |
National Astronomical Observatory of Japan, Japan | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q73w7/spectroscopic-and-asteroseismic-analysis-of-the-remarkable-main-sequence-a-star-kic-11145123
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