IIb or not IIb: A Catalog of ZTF Kilonova Imposters

TL;DR

This paper compiles a catalog of transient objects that mimic kilonovae, analyzing photometric features to distinguish true kilonovae from imposters without relying on spectroscopy.

Contribution

It introduces a comprehensive list of kilonova imposters, including IIb supernovae, and evaluates photometric criteria for their identification.

Findings

Identified key photometric differences between kilonovae and imposters.

Provided a classification catalog for fast optical transients.

Suggested methods to exclude imposters without spectroscopy.

Abstract

Among the various classes of fast optical transients (FOTs), kilonovae (KNe), which can emerge as a result of neutron star mergers, are extremely challenging to observe because of not only the rapid timescale on which they fade (on the order of days), but also due to the relative scarcity of their occurrence. This scarcity is compounded by the large number of other FOTs that may initially resemble the characteristic rise of a KNe. While these objects can be ruled out as candidate KNe by taking spectroscopy, a method of confidently ruling out transients based on photometric analysis alone would be incredibly valuable. We describe the compilation of various "imposter" transients, including a plurality of IIb SNe, and investigate a number of comparative metrics by which one might be able to remove transients from consideration without the use of spectroscopy. We provide a list of these objects and their classifications as well as a glossary of the transient types included in the sample.