Calcium Excess in Novae: Beyond Nuclear Physics Uncertainties

TL;DR

This study investigates the persistent overabundance of calcium in classical novae, finding that nuclear physics uncertainties do not explain the discrepancy, and discusses implications for measuring beryllium in nova ejecta.

Contribution

First Monte Carlo simulations assess nuclear reaction rate uncertainties' impact on nova calcium predictions, revealing these uncertainties cannot explain observed overabundances.

Findings

Nuclear reaction rate uncertainties do not account for Ca overabundance.

Ca lines are crucial for estimating 7Be in nova ejecta.

Alternative explanations for Ca overabundance are discussed.

Abstract

We examine Ca abundances in classical novae from spectroscopic observations spanning 65 years and investigate whether they are systematically high compared to those predicted by nova models. For the first time, we perform Monte Carlo simulations assessing the impact of nuclear reaction rate uncertainties on abundances predicted by multi-zone nova models. While the Ca abundances in the models are sensitive to variations of rates of the reactions 37Ar(p,gamma)38K and 38K(p,gamma)39Ca, the nuclear physics uncertainties of these reactions cannot account for the discrepancy between the observed and predicted Ca abundances in novae. Furthermore, the overabundance of Ca has important implications for measuring 7Be in nova ejecta, as Ca lines are used to estimate 7Be abundances. If the Ca abundance is incorrectly determined, it could lead to inaccurate 7Be abundance estimates. Possible alternative explanations for the observed Ca overabundance are discussed.