Towards rapid transient identification and characterization of kilonovae

TL;DR

This paper compares kilonova lightcurve models to improve electromagnetic counterpart identification for gravitational wave events, emphasizing the need for more realistic models to enhance parameter estimation and detection accuracy.

Contribution

It evaluates recent analytical and parametrized kilonova models against complex simulations, highlighting their potential for rapid transient identification.

Findings

Qualitative agreement between simple models and detailed simulations.

Improved models can help extract ejecta and binary parameters.

Combining gravitational-wave and kilonova data yields tighter constraints.

Abstract

With the increasing sensitivity of advanced gravitational wave detectors, the first joint detection of an electromagnetic and gravitational wave signal from a compact binary merger will hopefully happen within this decade. However, current gravitational-wave likelihood sky areas span $\sim 100-1000\,\textrm{deg}^2$, and thus it is a challenging task to identify which, if any, transient corresponds to the gravitational-wave event. In this study, we make a comparison between recent kilonovae/macronovae lightcurve models for the purpose of assessing potential lightcurve templates for counterpart identification. We show that recent analytical and parametrized models for these counterparts result in qualitative agreement with more complicated radiative transfer simulations. Our analysis suggests that with improved lightcurve models with smaller uncertainties, it will become possible to extract information about ejecta properties and binary parameters directly from the lightcurve measurement. Even tighter constraints are obtained in cases for which gravitational-wave and kilonovae parameter estimation results are combined. However, to be prepared for upcoming detections, more realistic kilonovae models are needed. These will require numerical relativity with more detailed microphysics, better radiative transfer simulations, and a better understanding of the underlying nuclear physics.