Impact of Ejecta Temperature and Mass on the Strength of Heavy Element Signature in Kilonova

Kilonova, the electromagnetic emission produced by compact binary mergers, is formed through a delicate interplay of physical processes, involving r-process nucleosynthesis and interactions between heavy elements and photons through radiative transfer. This complexity makes it difficult to achieve a comprehensive understanding of the kilonova spectrum. In this study, we aim to enhance our understanding and establish connections between physical parameters and observables through the radiative-transfer simulation. Specifically, we investigate how the ejecta temperature and element mass influence the resulting kilonova spectrum. For each species, the relative strength of its line features in the kilonova spectrum depends on these parameters, leading to the formation of a distinct region in the parameter space, named as the Prominent Signature Region (PSR), where the line signature of that species is notably evident in the kilonova spectrum. We explore the origin and applications of PSR. Among explored r-process elements (31<Z<92), we find that four species-Sr II, Y II, Ba II, and Ce II-exhibit large and strong PSR, suggesting their significant contributions to the kilonova spectrum in specific wavelengths. In addition, we discuss potential challenges and future perspectives in observable heavy elements and their masses in the context of PSR.

Further details can be found in Tak et al. (2024; arXiv: ). If you have any questions or comments, please contact Donggeun Tak (donggeun.tak@gmail.com).