# Optical and radio transients after the collapse of super-Chandrasekhar white dwarf merger remnants

## TL;DR

This paper explores the optical and radio transient signals produced by super-Chandrasekhar white dwarf merger remnants collapsing into neutron stars, highlighting the effects of surrounding dusty winds on observable emissions.

## Contribution

It introduces a model for dust-affected optical and radio transients following the collapse of super-Chandrasekhar white dwarf mergers, linking these signals to the remnants' properties.

## Key findings

- Dusty winds can suppress optical peak emission and create scattering plateaus.
- Shock interactions produce detectable radio transients over tens of days.
- Observations of these transients can reveal properties of white dwarf mergers and their gravitational wave contributions.

## Abstract

Super-Chandrasekhar remnants of double white dwarf mergers could sometimes collapse into a rapidly rotating neutron star (NS), accompanying with a mass ejection of a few times $0.01M_{\odot}$. Bright optical transient emission can be produced by the ejecta due to heating by radioactivities and particularly by energy injection from the NS. Since the merger remnants before collapse resemble a star evolving from the asymptotic giant branch phase to the planetary nebula phase, an intense dusty wind is considered to be driven about several thousand years ago before the collapse and surround the remnant at large radii. Therefore, the optical transient emission can be somewhat absorbed and scattered by the dusty wind, which can suppress the peak emission and cause a scattering plateau in optical light curves. Several years later, as the ejecta finally catches up with the wind material, the shock interaction between them can further give rise to a detectable radio transient emission on a timescale of tens of days. Discovery of and observations to such dust-affected optical transients and shock-driven radio transients can help to explore the nature of super-Chandrasekhar merger remnants and as well as the density and type ratios of double white dwarf systems, which is beneficial in assessing their gravitational wave contributions.