A CEMP-no star in the ultra-faint dwarf galaxy Pisces II
  A probable carbon enhanced metal-poor (CEMP) star, Pisces II 10694, was
discovered recently in the ultra-faint (UFD) galaxy Pisces II. This galaxy is
supposed to be very old, suspected to include dark matter, and likely formed
the bulk of its stars before the reionisation of the Universe.
  New abundances have been obtained from observations of Pisces II 10694 at the
Kueyen ESO VLT telescope, using the high-efficiency spectrograph: X-Shooter.
  We found that Pisces II 10694 is a CEMP-no star with [Fe/H]=-2.60 dex.
Careful measurements of the CH and C2 bands confirm the enhancement of the C
abundance ([C/Fe]=+1.23). This cool giant has very probably undergone extra
mixing and thus its original C abundance could be even higher. Nitrogen, O, Na,
and Mg are also strongly enhanced, but from Ca to Ni the ratios [X/Fe] are
similar to those observed in classical galactic very metal-poor stars. With its
low Ba abundance ([Ba/Fe] =-1.10 dex) Pisces II 10694 is a CEMP-no star. No
variation in the radial velocity could be detected between the years 2015 and
2017. The pattern of the elements abundance has a shape similar to the pattern
found in galactic CEMP-no stars like CS 22949-037 ([Fe/H]=-4.0) or SDSS
J1349+1407 ([Fe/H]=-3.6). The existence of a CEMP-no star in the UFD galaxy
Pisc II suggests that this small galaxy likely hosted zero-metallicity stars.
This is consistent with theoretical predictions of cosmological models
supporting the idea that UFD galaxies are the living fossils of the first
star-forming systems.
