A search for cool molecular gas in GK Persei and other classical novae

TL;DR

This study conducted a comprehensive search for molecular gas emissions in classical novae, finding no strong evidence of such emissions at millimeter and submillimeter wavelengths, but suggesting future detections are possible with advanced instruments.

Contribution

The paper provides the first extensive survey of molecular line emissions in classical novae, establishing their general faintness at these wavelengths and clarifying the nature of observed emissions around GK Per.

Findings

Classical novae are generally weak sources of molecular emission at millimeter/submillimeter wavelengths.

Observed CO emission around GK Per is from the interstellar medium, not the nova ejecta.

Future high-sensitivity observations may detect molecular emissions in some novae.

Abstract

Detecting molecular line emission from classical nova remnants has the potential of revealing information on the composition of the ejecta, in particular, it can deliver accurate isotopic ratios in the matter processed by a thermonuclear runaway. We conducted searches toward more than 100 classical novae for emission in lines of the CO or HCN molecules using single-dish telescopes and interferometric arrays at millimeter and submillimeter wavelengths. The survey demonstrates that classical novae, young or old, are not strong sources of molecular emission at submillimeter and millimeter wavelengths. Additionally, we mapped CO emission around Nova Persei 1901 (GK Per), earlier claimed to be circumstellar in origin. Our measurements indicate that the observed emission is from the interstellar medium. Although no molecular emission at millimeter and submillimeter wavelengths has been found in classical novae, it is still likely that some will be detected with high-sensitivity interferometers such as ALMA.