Spectroscopic and asteroseismic analysis of the remarkable main-sequence A star KIC 11145123

Abstract

A spectroscopic analysis was carried out to clarify the properties of KIC 11145123 -- the first main-sequence star with a determination of core-to-surface rotation -- based on spectra observed with the High Dispersion Spectrograph (HDS) of the Subaru telescope. The atmospheric parameters ($T_{\mathrm{eff}}=7600$ K, $\log g=4.2$, $\xi =3.1$ 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 $[Fe/H]=-0.71\pm 0.11$ dex and a high radial velocity of $-135.4\pm 0.2$ 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${}_{\odot }$. 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 (PM) technique.

arXiv comment19 pages, of which the final 7 are appendixed data tables. Ten figures, some of which do require colour. Accepted for publication in MNRAS

References in corpus (24)

• The chemical composition of the Sun
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Revised Stellar Properties of Kepler Targets for the Quarter 1-16 Transit Detection Run
• The r-Process Enriched Low Metallicity Giant HD 115444
• Asteroseismic measurement of surface-to-core rotation in a main sequence A star, KIC 11145123
• Stellar Parameters and Elemental Abundances of Late-G Giants
• Asteroseismic measurement of slow, nearly-uniform surface-to-core rotation in the main sequence F star KIC 9244992
• Abundances of C, N, O in slightly evolved stars in the globular clusters NGC 6397, NGC 6752 and 47 Tuc
• FM stars: A Fourier view of pulsating binary stars, a new technique for measuring radial velocities photometrically
• Discovery of Carbon/Oxygen depleted Blue Straggler Stars in 47 Tucanae: the chemical signature of a mass-transfer formation process
• Spectroscopic survey of Kepler stars. I. HERMES/Mercator observations of A- and F-type stars
• Asteroseismic modelling of the two F-type hybrid pulsators KIC10080943A and KIC10080943B
• Finding binaries among Kepler pulsating stars from phase modulation of their pulsations
• Blue Stragglers as Stellar Collision Products: the Angular Momentum Question
• Atmospheric velocity fields in tepid main sequence stars
• Deriving the orbital properties of pulsators in binary systems through their light arrival time delays
• The abundance pattern of the lambda Bootis stars
• An evaluation of the membership probability of 212 $\lambda$ Boo stars: I. A Catalogue
• Fast rotating Blue Stragglers in the globular cluster M4
• FLAMES and XSHOOTER spectroscopy along the two BSS sequences of M30
• Shape of a slowly rotating star measured by asteroseismology
• Lithium, Sodium, and Potassium Abundances in Sharp-Lined A-Type Stars
• HD 41641: A classical $\delta$ Sct-type pulsator with chemical signatures of an Ap star
• Another brick in understanding chemical and kinematical properties of BSSs: NGC 6752

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• Asteroseismic modeling of gravity modes in slowly rotating A/F stars with radiative levitation
• Reliability of stellar inclination estimated from asteroseismology: analytical criteria, mock simulations and Kepler data analysis
• Observations of Spin-Down in Post-Mast-Transfer Stars and the Possibility for Blue Straggler Gyrochronology
• Predictions for gravity-mode periods and surface abundances in intermediate-mass dwarfs from shear mixing and radiative levitation
• Calibrating angular momentum transport in intermediate-mass stars from gravity-mode asteroseismology
• The two-dimensional internal rotation of KIC11145123
• Semi-Analytical Expression of G-Mode Period Spacing: The Case of Brunt-Väisälä Frequency with Not a Jump But a Ramp
• Non-standard modeling of a possible blue straggler star, KIC 11145123