Elemental Abundances in the Ejecta of Old Classical Novae from Late-Epoch Spitzer Spectra

TL;DR

This study analyzes mid-infrared spectra of old classical novae to determine elemental abundances, revealing the white dwarf types involved and providing insights into ejecta composition and geometry years after eruption.

Contribution

First detection of neon emission in V1494 Aql and confirmation of white dwarf types in multiple novae through nebular analysis of late-time spectra.

Findings

V1974 Cyg and V382 Vel contain ONe white dwarfs.

V1494 Aql likely contains a CO white dwarf.

Spectra dominated by neon and oxygen emission lines.

Abstract

We present Spitzer Space Telescope mid-infrared IRS spectra, supplemented by ground-based optical observations, of the classical novae V1974 Cyg, V382 Vel, and V1494 Aql more than 11, 8, and 4 years after outburst respectively. The spectra are dominated by forbidden emission from neon and oxygen, though in some cases, there are weak signatures of magnesium, sulfur, and argon. We investigate the geometry and distribution of the late time ejecta by examination of the emission line profiles. Using nebular analysis in the low density regime, we estimate lower limits on the abundances in these novae. In V1974 Cyg and V382 Vel, our observations confirm the abundance estimates presented by other authors and support the claims that these eruptions occurred on ONe white dwarfs. We report the first detection of neon emission in V1494 Aql and show that the system most likely contains a CO white dwarf.