Mid-infrared Spectroscopic Observations of the Dust-forming Classical Nova V2676 Oph

TL;DR

This study presents mid-infrared spectroscopic observations of the dust-forming nova V2676 Oph, revealing its CO-rich white dwarf nature and detecting various dust grains and molecules, contributing to understanding nova compositions and evolution.

Contribution

First mid-infrared spectroscopic analysis of V2676 Oph confirming its CO-rich white dwarf and identifying dust and molecular features in its envelope.

Findings

No significant [Ne II] emission detected, indicating a CO-rich white dwarf.

Detection of carbon-rich and oxygen-rich grains in the nova envelope.

Presence of unidentified infrared feature from PAHs or hydrogenated amorphous carbon.

Abstract

The dust-forming nova V2676 Oph is unique in that it was the first nova to provide evidence of C_2 and CN molecules during its near-maximum phase and evidence of CO molecules during its early decline phase. Observations of this nova have revealed the slow evolution of its lightcurves and have also shown low isotopic ratios of carbon (12C/13C) and nitrogen (14N/15N) in its nova envelope. These behaviors indicate that the white dwarf (WD) star hosting V2676 Oph is a CO-rich WD rather than an ONe-rich WD (typically larger in mass than the former). We performed mid-infrared spectroscopic and photometric observations of V2676 Oph in 2013 and 2014 (respectively 452 and 782 days after its discovery). No significant [Ne II] emission at 12.8 micron was detected at either epoch. These provided evidence for a CO-rich WD star hosting V2676 Oph. Both carbon-rich and oxygen-rich grains were detected in addition to an unidentified infrared feature at 11.4 micron originating from polycyclic aromatic hydrocarbon molecules or hydrogenated amorphous carbon grains in the envelope of V2676 Oph.