Extending the Gaia Benchmark stars -- Optical vs. Infrared abundances

November 14 - 18 , 2022

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The Gaia Benchmark Stars (GBS) is an unprecedented sample of benchmark stars that already has proven to be valuable to (1) develop pipelines to determine atmospheric parameters and chemical abundances of stellar spectra (2) perform science verification on new instruments (3) calibrate the scales of parameters and abundances of large spectral data sets (4) test systematic uncertainties in spectral analyses using models and (5) build bridges between different spectroscopic surveys of the Milky Way (6) train young researchers in stellar spectroscopy.

The original GBS sample was put together 8 years ago, in 2014, and many advances have been achieved since then. In particular with stellar diameters from interferometry and Gaia parallaxes from DR3, where the original sample used Hipparcos parallaxes. This has now allowed us to increase the GBS sample from the original 38 stars to ~200 stars. The expanded sample will provide much better sampling of the HR-diagram. The expanded GBS sample is suggested as a calibration sample for SDSS-V, PLATO, WEAVE and 4MOST and as such is foreseen to be of the utmost importance in the years to come.

This workshop will serve to put together stellar spectroscopists to perform the aforementioned tests and so provide solid and comprehensive understanding of the uncertainties of the GBS chemical abundances. This will ensure the legacy of the GBS for the next decade. We will do this by performing tests that will stimulate and feed two key investigations: a) the comparison of elemental abundances obtained in the optical and the infrared in order to provide possible solutions when discrepancies are seen, and b) the impact of non-LTE and 3D effects in the infrared, an area that has seen great progress in the optical, but so far is only briefly studied in the infrared.

These items are crucial for putting the upcoming spectroscopic surveys onto the same scale whilst achieving accuracy on stellar abundances.