Search for associations containing young stars (SACY) VIII. An updated
  census of spectroscopic binary systems showing hints of non-universal
  multiplicity among these associations
  We seek to update the spectroscopy binary fraction of the SACY (Search for
Associations Containing Young stars) sample taking in consideration all
possible biases in our identification of binary candidates, such as activity
and rotation. Using high-resolution spectroscopic observations we have produced
$\sim$1300 cross-correlation functions (CCFs) to disentangle the previously
mentioned sources of contamination. The radial velocity values obtained were
cross-matched with the literature and were used to revise and update the
spectroscopic binary (SB) fraction in each of the SACY association. In order to
better describe the CCF profile, we calculated a set of high-order
cross-correlation features to determine the origin of the variations in radial
velocities. We identified 68 SB candidates from our sample of 410 objects. Our
results hint that the youngest associations have a higher SB fraction.
Specifically, we found sensitivity-corrected SB fractions of $22 \substack{+15
\\ -11} \%$ for $\epsilon$~Cha , $31 \substack{+16 \\ -14} \%$ for TW Hya and
$32 \substack{+9 \\ -8} \%$ for $\beta$~Pictoris, in contrast with the five
oldest ($\sim 35-125$ Myr) associations we have sampled which are $\sim 10\%$
or lower. This result seems independent of the methodology used to asses
membership to the associations. The new CCF analysis, radial velocity estimates
and SB candidates are particularly relevant for membership revision of targets
in young stellar associations. These targets would be ideal candidates for
follow-up campaigns using high-resolution techniques in order to confirm
binarity, resolve the orbits, and ideally calculate dynamical masses.
Additionally, if the results on SB fraction in the youngest associations are
confirmed, it could hint of non-universal multiplicity among SACY associations.
