The Neon Abundance in the Ejecta of QU Vul From Late-Epoch IR Spectra

TL;DR

This study analyzes late-epoch spectra of nova QU Vul to determine neon abundance, confirming a significant overabundance consistent with thermonuclear runaway on an ONeMg white dwarf, aligning with nucleosynthesis models.

Contribution

It provides the first detailed late-epoch spectral analysis of QU Vul's ejecta, quantifying neon overabundance over time, and confirms theoretical predictions of nucleosynthesis in such novae.

Findings

Neon is overabundant by over 76 times the solar value at first epoch.

Neon abundance increases to over 168 times the solar value at last epoch.

Results support the thermonuclear runaway model on an ONeMg white dwarf.

Abstract

We present ground-based SpectroCam-10 mid-infrared, MMT optical, and Spitzer Space Telescope IRS mid-infrared spectra taken 7.62, 18.75, and 19.38 years respectively after the outburst of the old classical nova QU Vulpeculae (Nova Vul 1984 #2). The spectra of the ejecta are dominated by forbidden line emission from neon and oxygen. Our analysis shows that neon was, at the first and last epochs respectively, more than 76 and 168 times overabundant by number with respect to hydrogen compared to the solar value. These high lower limits to the neon abundance confirm that QU Vul involved a thermonuclear runaway on an ONeMg white dwarf and approach the yields predicted by models of the nucleosynthesis in such events.