Back to the Lithium Plateau with J0023+0307 with [Fe/H]<-6. (arXiv:1904.04892v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Aguado_D/0/1/0/all/0/1">David S. Aguado</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hernandez_J/0/1/0/all/0/1">Jonay I. González Hernández</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Prieto_C/0/1/0/all/0/1">Carlos Allende Prieto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rebolo_R/0/1/0/all/0/1">Rafael Rebolo</a>
We present an analysis of the UVES high-resolution spectroscopic observations
at the 8.2m VLT of J0023+0307, a main-sequence extremely iron-poor dwarf star.
We are unable to detect iron lines in the spectrum but derive [Fe/H]<-6.1 from
the Ca II resonance lines assuming [Ca/Fe]>0.40. The chemical abundance pattern
of J0023+0307, with very low [Fe/Mg] and [Ca/Mg] abundance ratios, but
relatively high absolute Mg and Si abundances, suggests J0023+0307 is a second
generation star formed from a molecular cloud polluted by only one supernova in
which the fall-back mechanism played a role. We measure a carbon abundance of
A(C)=6.2 that places J0023+0307 on the low band in the A(C)-[Fe/H] diagram,
suggesting no contamination from a binary companion. This star is also unique
having a lithium abundance (A(Li)=2.02+-0.08) close to the level of the Lithium
Plateau, in contrast with lower Li determinations or upper limits in all other
extremely iron-poor stars. The upper envelope of the lithium abundances in
unevolved stars spanning more than three orders of magnitude in metallicity
(-6<[Fe/H]<-2.5) defines a nearly constant value. We argue that it is unlikely
that such uniformity is the result of depletion processes in stars from a
significantly higher initial Li abundance, but suggests instead a lower
primordial production, pointing to new physics such as decaying massive
particles, varying fundamental constants, or nuclear resonances, that could
have affected the primordial 7Li production.
We present an analysis of the UVES high-resolution spectroscopic observations
at the 8.2m VLT of J0023+0307, a main-sequence extremely iron-poor dwarf star.
We are unable to detect iron lines in the spectrum but derive [Fe/H]<-6.1 from
the Ca II resonance lines assuming [Ca/Fe]>0.40. The chemical abundance pattern
of J0023+0307, with very low [Fe/Mg] and [Ca/Mg] abundance ratios, but
relatively high absolute Mg and Si abundances, suggests J0023+0307 is a second
generation star formed from a molecular cloud polluted by only one supernova in
which the fall-back mechanism played a role. We measure a carbon abundance of
A(C)=6.2 that places J0023+0307 on the low band in the A(C)-[Fe/H] diagram,
suggesting no contamination from a binary companion. This star is also unique
having a lithium abundance (A(Li)=2.02+-0.08) close to the level of the Lithium
Plateau, in contrast with lower Li determinations or upper limits in all other
extremely iron-poor stars. The upper envelope of the lithium abundances in
unevolved stars spanning more than three orders of magnitude in metallicity
(-6<[Fe/H]<-2.5) defines a nearly constant value. We argue that it is unlikely
that such uniformity is the result of depletion processes in stars from a
significantly higher initial Li abundance, but suggests instead a lower
primordial production, pointing to new physics such as decaying massive
particles, varying fundamental constants, or nuclear resonances, that could
have affected the primordial 7Li production.
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