The origin of carbon-enhanced metal-poor ( CEMP ) stars and their possible connection with the chemical elements produced by the first stellar generation is still highly debated .
In contrast to the Galactic halo , not many CEMP stars have been found in the dwarf spheroidal galaxies around the Milky Way .
Here we present detailed abundances from ESO VLT/UVES high-resolution spectroscopy for ET0097 , the first CEMP star found in the Sculptor dwarf spheroidal , which is one of the best studied dwarf galaxies in the Local Group .
This star has \text { [ Fe / H ] } = -2.03 \pm 0.10 , \text { [ C / Fe ] } = 0.51 \pm 0.10 and \text { [ N / Fe ] } = 1.18 \pm 0.20 , which is the first nitrogen measurement in this galaxy .
The traditional definition of CEMP stars is \text { [ C / Fe ] } \geq 0.70 , but taking into account that this luminous red giant branch star has undergone mixing , it was intrinsically less nitrogen enhanced and more carbon-rich when it was formed , and so it falls under the definition of CEMP stars , as proposed by Aoki et al .
( 2007 ) to account for this effect .
By making corrections for this mixing , we conclude that the star had \text { [ C / Fe ] } \approx 0.8 during its earlier evolutionary stages .
Apart from the enhanced C and N abundances , ET0097 shows no peculiarities in other elements lighter than Zn , and no enhancement of the heavier neutron-capture elements ( Ba , La , Ce , Nd , Sm , Eu , Dy ) , making this a CEMP-no star .
However , the star does show signs of the weak r -process , with an overabundance of the lighter neutron-capture elements ( Sr , Y , Zr ) .
To explain the abundance pattern observed in ET0097 , we explore the possibility that this star was enriched by primordial stars .
In addition to the detailed abundances for ET0097 , we present estimates and upper limits for C abundances in 85 other stars in Sculptor derived from CN molecular lines , including 11 stars with \text { [ Fe / H ] } \leq - 2 .
Combining these limits with observations from the literature , the fraction of CEMP-no stars in Sculptor seems to be significantly lower than in the Galactic halo .