Surrogate light curve models for kilonovae with comprehensive wind ejecta outflows and parameter estimation for AT2017gfo

Atul Kedia, Marko Ristic, Richard O'Shaughnessy, Anjali B. Yelikar, Ryan T. Wollaeger, Oleg Korobkin, Eve A. Chase, Christopher L. Fryer, Christopher J. Fontes

Submitted on 8 November 2022


The electromagnetic emission resulting from neutron star mergers have been shown to encode properties of the ejected material in their light curves. The ejecta properties inferred from the kilonova emission has been in tension with those calculated based on the gravitational wave signal and numerical relativity models. Motivated by this tension, we construct a broad set of surrogate light curve models derived for kilonova ejecta. The four-parameter family of two-dimensional anisotropic simulations and its associated surrogate explore different assumptions about the wind outflow morphology and outflow composition, keeping the dynamical ejecta component consistent. We present the capabilities of these surrogate models in interpolating kilonova light curves across various ejecta parameters and perform parameter estimation for AT2017gfo both without any assumptions on the outflow and under the assumption that the outflow must be representative of solar \emph{r}-process abundance patterns. Our parameter estimation for AT2017gfo shows these new surrogate models help alleviate the ejecta property discrepancy while also illustrating the impact of systematic modeling uncertainties on these properties, urging further investigation.


Comment: 15 pages, 6 figures, data available in Zenodo and GitHub

Subject: Astrophysics - High Energy Astrophysical Phenomena


\textbf{Illustrating off-sample interpolations for two morphologies}. \emph{Top panel}: The bottom panel from Figure 4 of Ref. \cite{Ristic22} showing interpolation of various LCs versus time for the TPwind2 morphology adopted in that work. Different colors denote different filter bands, described in the legend. The dashed lines show full simulation output for each band. The colored points show our interpolated magnitude predictions at the evaluation times. The simulated parameters and viewing angle for this configuration are ($m_d/{\rm M}_\odot$, $v_d/c$, $m_w/{\rm M}_\odot$, $v_w/c$) = (0.097, 0.198, 0.084, 0.298) at $0^\circ$ \cite{Ristic22}. \emph{Bottom panel}: As above, but for the TSwind2 model morphology. The shaded region surrounding each solid curve shows our estimated GP fitting uncertainty at each time. The differences between these two panels illustrate the impact of outflow morphology on our results.