Preprint: Sculptor star DR20080 best matched by two metal-free supernovae

A team led by Francisco Cuadra has posted a preprint, arXiv:2611.13115, that is not yet peer-reviewed, on DR20080, an extremely metal-poor star in the Sculptor dwarf spheroidal galaxy. High-resolution spectra from the Very Large Telescope's UVES spectrograph yield abundances for 17 elements and upper limits for four more. The star has [Fe/H] = -3.26, mixing-corrected [C/Fe] = +1.60, and [Ba/Fe] = -1.28, the carbon-rich, barium-poor pattern labeled CEMP-no and long treated as a chemical heir of the first, metal-free stars.

Methods note: one star, VLT/UVES high-resolution spectra, 17 abundances and four limits; the progenitor story is a yield comparison, not an observed explosion, and n=1 cannot set a galaxy-wide rule. Oxygen is high at [O/Fe] = +1.53, above the Milky Way CEMP-no average in the preprint, while manganese and nickel are low ([Mn/Fe] = -1.02, [Ni/Fe] = -0.45). That oxygen-rich, barium-poor mix weighs against mass transfer from an asymptotic-giant-branch companion. Their preferred match is two metal-free events: a 43-solar-mass faint supernova at 0.6 times 10^51 erg, plus a 19.4-solar-mass hypernova at 10 times 10^51 erg.

CEMP-no stars are common in the Milky Way halo and ultra-faint dwarfs, yet scarce in classical dwarf spheroidals such as Sculptor, a gap often read as environmental dependence of the first stars. What a best-fit label hides is degeneracy. Faint-supernova fallback yields, following Heger and Woosley (2010), and fast-rotating spinstar models can both raise carbon relative to iron. A second explosion improves the match, but abundance uncertainties and yield choices mean two progenitors are not required by the data. On the abstract's numbers, carbon minus oxygen is about +0.07, so DR20080 is as oxygen-rich as it is carbon-rich.

Sculptor is massive enough that later generations should carry mixed supernova debris, so a star this iron-poor is a fossil of incomplete mixing, not a census of Population III. The uniqueness claim will stand or fall if other groups re-reduce the same UVES spectrum and if surveys find more Sculptor stars below [Fe/H] = -3. A fair test also needs spinstar yields beside supernova grids, with the evolutionary carbon correction stated explicitly. Until a second such star appears, any environmental rule for the first stars remains a hypothesis with a sample of one.