Gap Transients Interacting with Circumstellar Medium

TL;DR

This review discusses the discovery, observational features, and possible physical explanations of a recently identified class of transients that bridge the luminosity gap between supernovae and novae.

Contribution

It provides a comprehensive overview of the observational characteristics and physical models of gap transients, summarizing recent developments in understanding their nature.

Findings

Identification of a new class of transients in the luminosity gap

Classification into subgroups based on phenomenology

Summary of physical scenarios proposed for their origins

Abstract

In the last 20 years, modern wide-field surveys discovered a new class of peculiar transients, which lie in the luminosity gap between standard supernovae and classical novae. These transients are often called 'intermediate luminosity optical transients' or 'gap transients'. They are usually distinguished in subgroups based on their phenomenology, such as supernova impostors, intermediate luminosity red transients, and luminous red novae. In this review, we present a brief overview of their observational features and possible physical scenarios to date, in the attempt to understand their nature.