Bibcode
Beck, P. G.; do Nascimento, J.-D., Jr.; Duarte, T.; Salabert, D.; Tkachenko, A.; Mathis, S.; Mathur, S.; García, R. A.; Castro, M.; Pallé, P. L.; Egeland, R.; Montes, D.; Creevey, O.; Andersen, M. F.; Kamath, D.; van Winckel, H.
Bibliographical reference
Astronomy and Astrophysics, Volume 602, id.A63, 11 pp.
Advertised on:
6
2017
Journal
Citations
37
Refereed citations
27
Description
Context. Lithium abundance A(Li) and surface rotation are good
diagnostic tools to probe the internal mixing and angular momentum
transfer in stars. Aims: We explore the relation between surface
rotation, A(Li), and age in a sample of seismic solar-analogue stars,
and we study their possible binary nature. Methods: We selected a
sample of 18 solar-analogue stars observed by the NASA Kepler satellite
for an in-depth analysis. Their seismic properties and surface rotation
rates are well constrained from previous studies. About 53 h of
high-resolution spectroscopy were obtained to derive fundamental
parameters from spectroscopy and A(Li). These values were combined and
compared with seismic masses, radii, and ages, as well as with surface
rotation periods measured from Kepler photometry. Results: Based
on radial velocities, we identify and confirm a total of six binary star
systems. For each star, a signal-to-noise ratio of 80 ≲ S/N ≲
210 was typically achieved in the final spectrum around the lithium
line. We report fundamental parameters and A(Li). Using the surface
rotation period derived from Kepler photometry, we obtained a
well-defined relation between A(Li) and rotation. The seismic radius
translates the surface rotation period into surface velocity. With
models constrained by the characterisation of the individual mode
frequencies for single stars, we identify a sequence of three solar
analogues with similar mass ( 1.1 M⊙) and stellar ages
ranging between 1 to 9 Gyr. Within the realistic estimate of 7% for the
mass uncertainty, we find a good agreement between the measured A(Li)
and the predicted A(Li) evolution from a grid of models calculated with
the Toulouse-Geneva stellar evolution code, which includes rotational
internal mixing, calibrated to reproduce solar chemical properties. We
found a scatter in ages inferred from the global seismic parameters that
is too large when compared with A(Li). Conclusions: We present
the Li-abundance for a consistent spectroscopic survey of solar-analogue
stars with a mass of 1.00 ± 0.15 M⊙ that are
characterised through asteroseismology and surface rotation rates based
on Kepler observations. The correlation between A(Li) and
Prot supports the gyrochronological concept for stars younger
than the Sun and becomes clearer when the confirmed binaries are
excluded. The consensus between measured A(Li) for solar analogues with
model grids, calibrated on the Sun's chemical properties, suggests that
these targets share the same internal physics. In this light, the solar
Li and rotation rate appear to be normal for a star like the Sun.
Based on observations made with the NASA Kepler space telescope and the
Hermes spectrograph mounted on the 1.2 m Mercator Telescope at the
Spanish Observatorio del Roque de los Muchachos of the Instituto de
Astrofísica de Canarias.