# Impact of Pulsar and Fallback Sources on Multifrequency Kilonova Models

## TL;DR

This study investigates how pulsar and fallback accretion emissions influence kilonova brightness and color evolution, revealing fallback models better match observed trends but highlighting the need for further refinement.

## Contribution

It introduces detailed models of pulsar and fallback emissions affecting kilonova light curves, comparing their effects on observed color evolution and luminosity.

## Key findings

- Fallback models better match B and V magnitude evolution.
- Current models cannot simultaneously fit all observed light curves.
- Further parameter exploration is necessary for accurate modeling.

## Abstract

We explore the impact of pulsar electromagnetic dipole and fallback accretion emission on the luminosity of a suite of kilonova models. The pulsar models are varied over pulsar magnetic field strength, pulsar lifetime, ejecta mass, and elemental abundances; the fallback models are varied over fallback accretion rate and ejecta mass. For the abundances, we use Fe and Nd as representatives of the wind and dynamical ejecta, respectively. We simulate radiative transfer in the ejecta in either 1D spherical or 2D cylindrical spatial geometry. For the grid of 1D simulations, the mass fraction of Nd is 0, $10^{-4}$, or $10^{-3}$ and the rest is Fe. Our models that fit the bolometric luminosity of AT 2017gfo (the kilonova associated with the first neutron star merger discovered in gravitational waves, GW170817) do not simultaneously fit the B, V, and I time evolution. However, we find that the trends of the evolution in B and V magnitudes are better matched by the fallback model relative to the pulsar model, implying the time dependence of the remnant source influences the color evolution. Further exploration of the parameter space and model deficiencies is needed before we can describe AT 2017gfo with a remnant source.