A dusty rain falls on the nova V959 Monocerotis

TL;DR

This study analyzes infrared observations of nova V959 Mon, revealing unprecedented late dust emission likely caused by interaction of ejecta with circumbinary material, providing new insights into nova dust formation and evolution.

Contribution

It presents the first evidence of late-time dust emission in a nova, linked to ejecta interaction with pre-existing circumbinary material, and identifies the secondary star as a G5 main sequence star.

Findings

Detection of late dust emission at >600 days post-eruption.

Interpretation of dust behavior as due to ejecta-circumbinary interaction.

Observation of dust temperature increase and dust mass decline over time.

Abstract

We present archival and ground-based infrared observations of the gamma-ray-emitting nova V959 Mon, covering the period 100-4205 days after the 2012 eruption. We use these data to determine that the secondary in the nova system is a G5 main sequence star. Data from the NEOWISE survey reveal a significant increase in the emission at 3.4 microns and 4.6 microns at late (>~600 days) times, which we interpret as emission by dust. Other interpretations are considered but cannot be reconciled with the data. The presence of such late dust emission, and in particular its variation with time, are unprecedented in the context of novae. The behaviour of the dust emission suggests a qualitative interpretation in which ejecta from the 2012 eruption encounter denser pre-eruption circumbinary material, giving rise to Rayleigh-Taylor instabilities that cause clumps of dust-bearing material to fall back towards the central binary, the dust undergoing destruction by chemisputtering as it does so. The observed rise in the dust temperature, the decline in the nova-dust distance and in the dust mass, are consistent with this interpretation. Not all novae are expected to show this behaviour, but inspection of resources such as NEOWISE might reveal other novae post-eruption that do.