On the 12C/13C isotopic ratio at the dawn of chemical evolution
arXiv:2309.11664 · doi:10.1051/0004-6361/202347676
Abstract
The known Mega and Hyper Metal-Poor (MMP-HMP) stars with [Fe/H]<-6.0 and <-5.0, respectively, likely belong to the CEMP-no class, i.e. carbon-enhanced stars with low or absent second peak neutron capture elements. They are likely second generation stars and the few elements measurable in their atmospheres are used to infer the properties of single or very few progenitors. The high carbon abundance in the CEMP-no stars offers a unique opportunity to measure the carbon isotopic ratio, which directly monitors the presence of mixing between the He and H-burning layers either within the star or in the progenitor(s). By means of high-resolution spectra acquired with the ESPRESSO spectrograph at the VLT we aim to derive values for the 12C/13C ratio at the lowest metallicities. A spectral synthesis technique based on the SYNTHE code and on ATLAS models is used within a Markov-chain Monte Carlo methodology to derive 12C/13C in the stellar atmospheres of five of the most metal poor stars. These are the Mega Metal-Poor giant SMS J0313-6708 ([Fe/H]<-7.1), the Hyper Metal-Poor dwarf HE1327-2326 ([Fe/H]=-5.8),the Hyper Metal-Poor giant SDSS J1313-0019 ([Fe/H] = -5.0) and the Ultra Metal-Poor subgiant HE0233-0343 ([Fe/H]=-4.7). We also revise a previous value for the Mega Metal-Poor giant SMSS J1605-1443 with ([Fe/H] = -6.2). In four stars we derive an isotopic value while for HE1327-2326 we provide a lower limit. All Measurements are in the range 39<12C/13C<100 showing that the He- and H-burning layers underwent partial mixing either in the stars or, more likely, in their progenitors. This provides evidence of a primary production of 13C at the dawn of chemical evolution. [abridged]
10 pages, 6 figure, accepted A&A
References in corpus (30)
- Nucleosynthetic signatures of the first stars
- CH in stellar atmospheres: an extensive linelist
- TOPoS: II. On the bimodality of carbon abundance in CEMP stars. Implications on the early chemical evolution of galaxies
- Binarity in Carbon-Enhanced Metal-Poor stars
- First stars IX -Mixing in extremely metal-poor giants. Variation of the 12C/13C, [Na/Mg] and [Al/Mg] ratios
- HE 1327-2326, an unevolved star with [Fe/H]<-5.0. II. New 3D-1D corrected abundances from a VLT/UVES spectrum
- An Elemental Assay of Very, Extremely, and Ultra Metal-Poor Stars
- First stars X. The nature of three unevolved Carbon-Enhanced Metal-Poor stars
- Exploring the Origin of Lithium, Carbon, Strontium and Barium with four new Ultra Metal-Poor Stars
- A new imprint of fast rotators: low 12C/13C ratios in extremely metal-poor halo stars
- Elemental abundances and classification of CEMP stars
- The R-process Alliance: First Magellan/MIKE Release from the Southern Search for R-Process-enhanced Stars
- The first stars: CEMP--no stars and signatures of spinstars
- 3D NLTE analysis of the most iron-deficient star, SMSS0313-6708
- Faint Population III supernovae as the origin of the most iron-poor stars
- The lowest detected stellar Fe abundance: The halo star SMSS J160540.18-144323.1
- Lithium abundances in CEMP stars
- Broadband UBVRI Photometry of Horizontal-Branch and Metal-Poor Candidates from the HK and Hamburg/ESO Surveys. I
- Back to the Lithium Plateau with J0023+0307 with [Fe/H]<-6
- An equatorial ultra iron-poor star identified in BOSS
- The ESO UVES Advanced Data Products Quasar Sample - III. Evidence of Bimodality in the [N/alpha] Distribution
- TOPoS: III. An ultra iron-poor multiple CEMP system
- J0815+4729: A chemically primitive dwarf star in the Galactic Halo observed with Gran Telescopio Canarias
- Discovery of a thin lithium plateau among metal-poor red giant branch stars
- New ultra metal-poor stars from SDSS: follow-up GTC medium-resolution spectroscopy
- Carbon, isotopic ratio C/C and nitrogen in solar twins: constraints for the chemical evolution of the local disc
- Unusual Isotopic Abundances in a Fully-Convective Stellar Binary
- Espresso observations of HE 01075240 and other CEMP-no stars with
- On the dearth of C-enhanced metal-poor stars in the Galactic bulge
- 12C/13C ratio and CNO abundances in the classical very old metal-poor dwarf HD 140283