The Gaia-ESO Survey: Spectroscopic-asteroseismic analysis of K2 stars in
  Gaia-ESO
  The extensive stellar spectroscopic datasets that are available for studies
in Galactic Archeaology thanks to, for example, the Gaia-ESO Survey, now
benefit from having a significant number of targets that overlap with
asteroseismology projects such as Kepler, K2 and CoRoT. Combining the
measurements from spectroscopy and asteroseismology allows us to attain greater
accuracy with regard to the stellar parameters needed to characterise the
stellar populations of the Milky Way. The aim of this Gaia-ESO Survey special
project is to produce a catalogue of self-consistent stellar parameters by
combining measurements from high-resolution spectroscopy and precision
asteroseismology. We carried out an iterative analysis of 90 K2@Gaia-ESO red
giants. The spectroscopic values of Teff were used as input in the seismic
analysis to obtain log(g) values. The seismic estimates of log(g) were then
used to re-determine the spectroscopic values of Teff and [Fe/H]. Only one
iteration was required to obtain parameters that are in good agreement for both
methods and thus, to obtain the final stellar parameters. A detailed analysis
of outliers was carried out to ensure a robust determination of the parameters.
The results were then combined with Gaia DR2 data to compare the seismic log(g)
with a parallax-based log(g) and to investigate instances of variations in the
velocity and possible binaries within the dataset. This analysis produced a
high-quality catalogue of stellar parameters for 90 red giant stars observed by
both K2 and Gaia-ESO that were determined through iterations between
spectroscopy and asteroseismology. We compared the seismic gravities with those
based on Gaia parallaxes to find an offset which is similar to other studies
that have used asteroseismology. Our catalogue also includes spectroscopic
chemical abundances and radial velocities, as well as indicators for possible
binary detections.
