Detecting weak beryllium lines with CUBES
  Beryllium is a light element with one single stable isotope, 9Be, which is a
pure product of cosmic-ray spallation in the interstellar medium. Beryllium
abundances in late-type stars can be used in studies about evolutionary mixing,
Galactic chemical evolution, planet engulfment, and the formation of globular
clusters. Some of these uses of Be abundances figure among the science cases of
the Cassegrain U-Band Efficient Spectrograph (CUBES), a new near-UV low- and
medium-resolution spectrograph under development for the Very Large Telescope.
Here, we report on a study about beryllium abundances in extremely metal-poor
stars in the context of the phase A of CUBES. Our motivation is to understand
the limits for the detection of weak lines in extremely metal-poor stars of low
Be abundances. We analyze simulated CUBES observations, performed in
medium-resolution mode, based on synthetic spectra for four mock stars with
[Fe/H] \leq -3.0. We find that detecting the Be lines is possible in certain
cases, but is very challenging and requires high signal-to-noise ratio.
Depending on the atmospheric parameters of the target stars, and if
signal-to-noise per pixel of about 400 can be achieved, it should be possible
to detect Be abundances between log(Be/H) = -13.1 and -13.6, with a typical
uncertainty of \pm 0.15 dex. Using CUBES, the required data for such studies
can be obtained for stars that are fainter by two magnitudes with respect to
what is possible with current instrumentation.
