Optical and Near-Infrared Photometry of Nova V2362 Cyg : Rebrightening Event and Dust Formation

TL;DR

This study presents detailed optical and near-infrared observations of nova V2362 Cyg, revealing a rebrightening event, dust formation, and the evolution of the nova's pseudophotosphere, providing insights into dust production in novae.

Contribution

It provides the first detailed multiwavelength photometric analysis of the rebrightening and dust formation in V2362 Cyg, highlighting the interaction of outflows and dust grain formation.

Findings

Rebrightening occurred 100-240 days after maximum.

Dust formation was confirmed with a dust mass estimate of 10^(-8) to 10^(-10) solar masses.

Optical and NIR fluxes during rebrightening fit blackbody radiation at 1500 K.

Abstract

We present optical and near-infrared (NIR) photometry of a classical nova, V2362 Cyg (= Nova Cygni 2006). V2362 Cyg experienced a peculiar rebrightening with a long duration from 100 to 240 d after the maximum of the nova. Our multicolor observation indicates an emergence of a pseudophotosphere with an effective temperature of 9000 K at the rebrightening maximum. After the rebrightening maximum, the object showed a slow fading homogeneously in all of the used bands for one week. This implies that the fading just after the rebrightening maximum ( less or equal 1 week ) was caused by a slowly shrinking pseudophotosphere. Then, the NIR flux drastically increased, while the optical flux steeply declined. The optical and NIR flux was consistent with blackbody radiation with a temperature of 1500 K during this NIR rising phase. These facts are likely to be explained by dust formation in the nova ejecta. Assuming an optically thin case, we estimate the dust mass of 10^(-8) -- 10^(-10) M_solar, which is less than those in typical dust-forming novae. These results support the senario that a second, long-lasting outflow, which caused the rebrightening, interacted with a fraction of the initial outflow and formed dust grains.