Rebrightening Phenomenon in Classical Novae

TL;DR

This paper analyzes the rebrightening phenomena in classical novae V1493 Aql and V2362 Cyg, proposing a shock breakout model involving secondary ejection and explaining various unusual nova behaviors.

Contribution

It introduces a schematic interpretation of nova rebrightenings as shock breakouts from secondary ejections, linking light curve features to shock physics.

Findings

Rebrightening light curves fit a combined power-law decline and exponential brightening model.

Shock breakout from secondary ejection explains rapid fading after rebrightening.

The model accounts for early variations and dust formation in novae.

Abstract

Two classical novae V1493 Aql and V2362 Cyg were known to exhibit unprecedented large-amplitude rebrightening during the late stage of their evolution. We analyzed common properties in these two light curves. We show that these unusual light curves are very well expressed by a combination of power-law decline, omnipresent in fast novae, and exponential brightening. We propose a schematic interpretation of the properties common to these rebrightenings can be a consequence of a shock resulting from a secondary ejection and its breakout in the optically thick nova winds. This interpretation has an advantage in explaining the rapid fading following the rebrightening and the subsequent evolution of the light curve. The exponential rise might reflect emerging light from the shock front, analogous to a radiative precursor in a supernova shock breakout. The consequence of such a shock in the nova wind potentially explains many kinds of unusual phenomena in novae including early-stage variations and potentially dust formation.