title: Nucleosynthetic signatures of the first stars.
abstract: The chemically most primitive stars provide constraints on the nature of the first stellar objects that formed in the Universe; elements other than hydrogen, helium and traces of lithium present within these objects were generated by nucleosynthesis in the very first stars. The relative abundances of elements in the surviving primitive stars reflect the masses of the first stars, because the pathways of nucleosynthesis are quite sensitive to stellar masses. Several models have been suggested to explain the origin of the abundance pattern of the giant star HE0107-5240, which hitherto exhibited the highest deficiency of heavy elements known. Here we report the discovery of HE1327-2326, a subgiant or main-sequence star with an iron abundance about a factor of two lower than that of HE0107-5240. Both stars show extreme overabundances of carbon and nitrogen with respect to iron, suggesting a similar origin of the abundance patterns. The unexpectedly low Li and high Sr abundances of HE1327-2326, however, challenge existing theoretical understanding: no model predicts the high Sr abundance or provides a Li depletion mechanism consistent with data available for the most metal-poor stars.
authors.affiliation: Research School of Astronomy & Astrophysics, The Australian National University, Cotter Road, Weston Creek, Australian Capital Territory 2611, Australia. anna@mso.anu.edu.au
authors.forename: Anna
authors.initials: A
authors.lastname: Frebel
authors.forename: Wako
authors.initials: W
authors.lastname: Aoki
authors.forename: Norbert
authors.initials: N
authors.lastname: Christlieb
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Ando
authors.forename: Martin
authors.initials: M
authors.lastname: Asplund
authors.forename: Paul S
authors.initials: PS
authors.lastname: Barklem
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Beers
authors.forename: Kjell
authors.initials: K
authors.lastname: Eriksson
authors.forename: Cora
authors.initials: C
authors.lastname: Fechner
authors.forename: Masayuki Y
authors.initials: MY
authors.lastname: Fujimoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Honda
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Kajino
authors.forename: Takeo
authors.initials: T
authors.lastname: Minezaki
authors.forename: Ken'ichi
authors.initials: K
authors.lastname: Nomoto
authors.forename: John E
authors.initials: JE
authors.lastname: Norris
authors.forename: Sean G
authors.initials: SG
authors.lastname: Ryan
authors.forename: Masahide
authors.initials: M
authors.lastname: Takada-Hidai
authors.forename: Stelios
authors.initials: S
authors.lastname: Tsangarides
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Yoshii