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An unexplored enrichment stochasticity and its implications for stellar abundance patterns

Anmol Aggarwal, Ralph Schoenrich

Abstract

Extremely low metallicity stars are intensely studied as they take observations the closest to the very first generations of stars in the universe. Widely assumed to be enriched by just one dying massive star, some of these very metal poor stars have abnormal chemical abundance ratios and have been taken to reflect a rare hypernova (with high explosion energy $\gtrsim \ 10^{52}$ erg.). Here we remodel the enrichment of three such stars and show that their abundances are better explained by enrichment from a normal (less energetic) supernova accounting for inhomogeneous distribution of the ejecta. This work establishes the importance of the inhomogeneity of supernovae, serves as a template for a required reassessment of all metal-poor/peculiar stars, and raises the need to quantify this inhomogeneity both in theory and in observations.

An unexplored enrichment stochasticity and its implications for stellar abundance patterns

Abstract

Extremely low metallicity stars are intensely studied as they take observations the closest to the very first generations of stars in the universe. Widely assumed to be enriched by just one dying massive star, some of these very metal poor stars have abnormal chemical abundance ratios and have been taken to reflect a rare hypernova (with high explosion energy erg.). Here we remodel the enrichment of three such stars and show that their abundances are better explained by enrichment from a normal (less energetic) supernova accounting for inhomogeneous distribution of the ejecta. This work establishes the importance of the inhomogeneity of supernovae, serves as a template for a required reassessment of all metal-poor/peculiar stars, and raises the need to quantify this inhomogeneity both in theory and in observations.

Paper Structure

This paper contains 19 sections, 3 equations, 13 figures, 6 tables.

Table of Contents

  1. Introduction
  2. The AS0039 star
  3. HE 1327-2326
  4. J0931+0038
  5. Underlying issues
  6. Theory and Methods
  7. Statistical model construction
  8. Models
  9. AS0039 fit
  10. C abundance
  11. Na and Al abundances
  12. Mg, Si, Ca, and Ti abundances
  13. Sc, Cr, Mn, Co, Ni, and Zn abundances
  14. HE 1327-2326 fit
  15. J0931+0038 fit
  16. ...and 4 more sections

Figures (13)

  • Figure 1: Comparison of Skúladóttir_2024's 20 $\textup{M}_\odot$ hypernova model fit and the predicted chemical abundance pattern obtained by using the method presented in this work with limongi2018's 13 $\textup{M}_\odot$ model.
  • Figure 2: The log mass coordinate (MC) of the 13 $\textup{M}_\odot$ model star vs. the contribution coefficients ($a_i$, on a log scale) resulting from fitting the AS0039 observations. The values of coefficients have been marked at the beginning of their respective regions. The solid line marks the end of the last region.
  • Figure 3: Comparison of our normal (15 $M_{\odot}$ SN fit with the HE 1327-2326 hypernova fit (upper limits not shown). See Fig. \ref{['fig:HE_ul_fit']} for a plot with upper limits.
  • Figure 4: Same as Fig. \ref{['fig:coeff']}, but for 15 $\textup{M}_\odot$ model star and HE 1327-2326.
  • Figure 5: Comparison of our normal (13 $M_{\odot}$ SN fit with the J0931+0038 hypernova fit (upper limits not shown). See Fig. \ref{['fig:80_SM_ul_fit']} for a plot with upper limits.
  • ...and 8 more figures