Toward Rapid Transient Identification and Characterization of Kilonovae

With the increasing sensitivity of advanced gravitational-wave (GW) detectors, the first joint detection of an electromagnetic and GW signal from a compact binary merger will hopefully happen within this decade. However, current GW likelihood sky areas span ∼ 100-1000 deg², and thus it is a challenging task to identify which, if any, transient corresponds to the GW event. In this study, we make a comparison between recent kilonova/macronova light-curve models for the purpose of assessing potential light-curve templates for counterpart identification. We show that recent analytical and parameterized models for these counterparts result in qualitative agreement with more complicated radiative transfer simulations. Our analysis suggests that with improved light-curve models with smaller uncertainties it will become possible to extract information about ejecta properties and binary parameters directly from the light-curve measurement. Even tighter constraints are obtained in cases for which GW and kilonova parameter estimation results are combined. It will therefore be important to make comparisons and potentially combine parameter estimation with the kilonova and GW results. However, to be prepared for upcoming detections, more realistic kilonova 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.