Phosphorus enrichment by ONe novae in the Galaxy

TL;DR

This paper introduces new models showing that phosphorus enrichment in the Galaxy can be explained by oxygen-neon novae, matching observed trends better than previous supernova-only models, and predicts specific abundance trends for future observational testing.

Contribution

The study presents the first models incorporating phosphorus enrichment from ONe novae, explaining observed [P/Fe] trends with metallicity and providing testable predictions.

Findings

[P/Fe] decreases with increasing [Fe/H] for [Fe/H] > -1.

Models with ONe novae better reproduce observed phosphorus trends.

Predicted similar trends for [Cl/Fe] due to large yields from ONe novae.

Abstract

Recent observations have shown that [P/Fe] in the Galactic stars decreases with increasing [Fe/H] for [Fe/H] > -1 whereas it is almost subsolar for [Fe/H]< -2. These [P/Fe] trends with [Fe/H] have not been well reproduced by previous theoretical models incorporating phosphorus (P) enrichment only by core collapse supernoave. We here show, for the first time, that the trends can be naturally explained by our new models incorporating P enrichment by oxygen-neon (ONe) novae which occur at the surface of massive white dwarfs whose masses are larger than 1.25 M_sun with a metallicity-dependence rate. We also show that the observations can be better reproduced by the models by assuming that (i) the total mass of gaseous ejecta per ONe nov (M_ej) is as high as 4 * 10^{-5} M_sun and (ii) the number of such novae per unit mass (N_ONe) is as large as 0.01 at [Fe/H]~-3. The assumed M_ej is consistent with observations, and the high N_ONe is expected from recent theoretical models for ONe nova fractions. We predict that (i) [P/Fe] increases with increasing [Fe/H] for -2 < [Fe/H] < -1 and (ii) [P/Fe] and [Cl/Fe] trends with [Fe/H] are very similar with each other due to very large yields of P and Cl from ONe nova. It is thus worthwhile for future observations to assess the validity of the proposed P enrichment by ONe novae by confirming or ruling out these two predictions.