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Title: The origin of the most iron-poor star

We investigate the origin of carbon-enhanced metal-poor (CEMP) stars starting from the recently discovered [Fe/H] < -7.1 star SMSS J031300. We show that the elemental abundances observed on the surface of SMSS J031300 can be well fit by the yields of faint, metal-free, supernovae (SNe). Using properly calibrated faint SN explosion models, we study, for the first time, the formation of dust grains in such carbon-rich, iron-poor SN ejecta. Calculations are performed assuming both unmixed and uniformly mixed ejecta and taking into account the partial destruction by the SN reverse shock. We find that, due to the paucity of refractory elements beside carbon, amorphous carbon is the only grain species to form, with carbon condensation efficiencies that range between (0.15 and 0.84), resulting in dust yields in the range (0.025-2.25) M {sub ☉}. We follow the collapse and fragmentation of a star-forming cloud enriched by the products of these faint SN explosions and we explore the role played by fine structure line cooling and dust cooling. We show that even if grain growth during the collapse has a minor effect of the dust-to-gas ratio, due to C depletion into CO molecules at an early stage of the collapse, the formationmore » of CEMP low-mass stars, such as SMSS J031300, could be triggered by dust cooling and fragmentation. A comparison between model predictions and observations of a sample of C-normal and C-rich metal-poor stars supports the idea that a single common pathway may be responsible for the formation of the first low-mass stars.« less
Authors:
; ;  [1] ; ;  [2] ;  [3] ;  [4] ;  [5]
  1. INAF/Osservatorio Astronomico di Roma, Via di Frascati 33, I-00040 Monteporzio (Italy)
  2. Department of Physics, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan)
  3. Astronomical Institute, Tohoku University, Sendai 980-8578 (Japan)
  4. National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)
  5. INAF/IASF, Via Fosso del Cavaliere 100, I-00133 Roma (Italy)
Publication Date:
OSTI Identifier:
22370430
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 794; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; CARBON; CARBON MONOXIDE; COMPARATIVE EVALUATIONS; COOLING; DUSTS; EFFICIENCY; FINE STRUCTURE; FORECASTING; FRAGMENTATION; GRAIN GROWTH; IRON; MASS; MOLECULES; REFRACTORIES; STARS; SUPERNOVA REMNANTS; SUPERNOVAE; SURFACES