A Galactic Perspective on the (Unremarkable) Relative Refractory Depletion Observed in the Sun

Abstract

Over the last two decades, the Sun has been observed to be depleted in refractory elements as a function of elemental condensation temperature (\tcond) relative to $\sim 80\%$ of its counterparts. We assess the impact of Galactic chemical evolution (GCE) on refractory element--\tcond\ trends for 109,500 unique solar analogs from the GALAH, APOGEE, Gaia RVS, and \cite{bedell18} surveys. We find that a star's \feh\ and \alphafe\ are predictive of its \tcond\ slope (\rsq\ = $15\pm 5\%$, $23\pm 10\%$ respectively) while \teff\ and \logg\ contribute more weakly (\rsq\ = $9\pm 5\%$, $13\pm 16\%$). The Sun's abundance pattern resembles that of more metal-rich (0.1 dex) and $\hat{I}\pm$-depleted stars ($-0.02$ dex), suggesting a connection to broader GCE trends. To more accurately model stars' nucleosynthetic signatures, we apply the K-process model from \cite{Griffith24}, which casts each star's abundance pattern as a linear combination of core-collapse and Type Ia supernovae contributions. We find the Sun appears chemically ordinary in this framework, consistent with the intrinsic population scatter expected from stellar nucleosynthesis. We show that refractory element--\tcond\ trends arise because elements with higher \tcond\ have higher contributions from core-collapse supernovae. Refractory element depletion trends primarily reflect nucleosynthetic enrichment patterns shaped by GCE and local ISM inhomogeneities, with these processes accounting for $>90\%$ of the observed variation within $2\ddot{I}ƒ$. This work highlights how abundance diversity due to local and global chemical enrichment complicates the interpretation of population-scale planet-related chemical signatures in current datasets.

38 pages, 12 figures, 3 tables, 2 appendices. Accepted in ApJ