The R-Process Alliance

For each star, we inspected over 1400 individual absorption lines using a combination of equivalent width measurements and spectral synthesis. The analysis was conducted under the assumption of one-dimensional local thermodynamic equilibrium, employing the MOOG radiative transfer code. We derived abundances for 54 chemical species, including 29 neutron-capture (n-capture) elements covering the full mass range of the r-process abundance pattern.

A kinematic analysis reveals that stars likely originated from ten kinematically distinct systems. Based on this assumption, we use the sample to probe the maximum variation expected from ten independent r-process nucleosynthesis events and compute the intrinsic dispersion of each element relative to Zr and Eu, for the light and heavy r-process elements, respectively. This exercise results in a remarkably low cosmic scatter across the ten r-process sites enriching these stars, for the rare earth and third peak elements, for example, we find {sigma}[La/Eu]=0.08 and {sigma}[Os/Eu]=0.11dex while the scatter between light and heavy, {sigma}[Zr/Eu] is slightly higher at 0.18dex.

The elemental abundance patterns across the ten independent r-process sites show remarkably small cosmic dispersions. This minimal dispersion suggests a high degree of uniformity in r-process yields across diverse astrophysical environments.