GEPI

Chemical evolution of the Large Magellanic Cloud

The Large Magellanic Cloud (LMC) is among the closest galaxy to the
Milky Way. The LMC exhibits a stellar bar-shaped structure at its
center, embedded in an older stellar disc. The LMC is almost face-on
which is ideal to sample the bar’s and disc’s stellar populations. In
order to investigate the relation between the LMC bar and disc, we
performed a detailed chemical analysis of more than 250 LMC RGB stars
located in three different fields : a first field located on the bar, a
second in the inner disc at 2° South of the bar, and a third in the
outer parts of the LMC disc, at 4° from the bar. Thanks to a broad
spectral coverage ( 1000A), we are able to measure abundances for many
elements belonging to main elemental families (alpha, iron-peak, heavy
s- and r-process). Here, we focus on the alpha-element abundances (O,
Mg, Ca, Si and Ti), compare the trends for the three LMC fields and
discuss them in terms of chemical evolution.

Double and triple stellar systems in GES iDR5

Binary systems are ideal targets to test theories of stellar formation,
stellar evolution and nucleosynthesis. Numerous questions are still open
and among them, that of the frequency of binary systems. A crucial step
to shed new light on this topic is to identify and characterize those
objects. Thanks to the high-accuracy radial velocities brought by the
Gaia-ESO survey (GES), it is possible to hunt new multiple stellar
systems across the Milky Way. We exploit the numerous GIRAFFE HR10 and
HR21 spectra of the GES to detect spectroscopic multiple system
candidates (SBn, n≥2). To this end, we improved the computation of HR21
cross-correlation functions (CCF) and we improved the tool DOE,
developed at IAA, which automatically detects multi-peaked
cross-correlation functions. We present here the results of this
analysis applied to the GES iDR5. Compared to our results for iDR4, this
analysis benefits from an increased number of recorded spectra and from
the careful re-computation of the CCFs, which allows to significantly
improve the number of detected binaries.