Identifying Kilonovae in the Presence of Optical Afterglow for the Wide Field Survey Telescope
Abstract
Identifying kilonovae associated with binary neutron star mergers is often complicated by the presence of a dominant synchrotron afterglow. In this work, we evaluate the performance of the Wide Field Survey Telescope (WFST) in identifying kilonova signals in composite afterglow-kilonova transients. Using a numerical framework based on the Fisher information matrix, we simulate $10,000$ realizations for each of two scenarios: an AT2017gfo-based template model and a physically sampled population that accounts for kilonova diversity. Our results indicate that kilonova identification is primarily limited by source distance. In both scenarios, the identification efficiency is largely insensitive to variations in afterglow microphysical parameters and exceeds 80% at distances within approximately 600 Mpc for AT2017gfo-like events. Under our adopted assumptions and a short gamma-ray burst (sGRB)-triggered target-of-opportunity (ToO) observational strategy, we estimate that the WFST could identify 0.1−1.2 kilonovae per year in the optimistic scenario. Furthermore, we find that the discriminating power of color-based filters rapidly saturates, reaching a stable plateau by the second night after the merger. We therefore propose a staged observing strategy that prioritizes high-cadence g and r-band monitoring during the first night and incorporates the z band from the second night onward. This strategy improves the identification precision by exploiting the increasingly prominent red excess produced by the kilonova. Our results provide a physical basis for optimizing WFST observing resources to efficiently detect and characterize kilonovae in the multimessenger era.
Versions
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BibTeX
@misc{yang2026identifying,
title = {{Identifying Kilonovae in the Presence of Optical Afterglow for the Wide Field Survey Telescope}},
author = {Huan Yang and Zhengyan Liu and Liang-Duan Liu and Wen Zhao and Zigao Dai},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2607.20233},
eprint = {2607.20233},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.20233},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Identifying Kilonovae in the Presence of Optical Afterglow for the Wide Field Survey Telescope
AU - Huan Yang
AU - Zhengyan Liu
AU - Liang-Duan Liu
AU - Wen Zhao
AU - Zigao Dai
PY - 2026
DA - 2026/09/18
PB - arXiv
DO - 10.48550/arxiv.2607.20233
UR - https://arxiv.org/abs/2607.20233
AB - Identifying kilonovae associated with binary neutron star mergers is often complicated by the presence of a dominant synchrotron afterglow. In this work, we evaluate the performance of the Wide Field Survey Telescope (WFST) in identifying kilonova signals in composite afterglow-kilonova transients. Using a numerical framework based on the Fisher information matrix, we simulate $10,000$ realizations for each of two scenarios: an AT2017gfo-based template model and a physically sampled population that accounts for kilonova diversity. Our results indicate that kilonova identification is primarily limited by source distance. In both scenarios, the identification efficiency is largely insensitive to variations in afterglow microphysical parameters and exceeds 80% at distances within approximately 600 Mpc for AT2017gfo-like events. Under our adopted assumptions and a short gamma-ray burst (sGRB)-triggered target-of-opportunity (ToO) observational strategy, we estimate that the WFST could identify 0.1−1.2 kilonovae per year in the optimistic scenario. Furthermore, we find that the discriminating power of color-based filters rapidly saturates, reaching a stable plateau by the second night after the merger. We therefore propose a staged observing strategy that prioritizes high-cadence g and r-band monitoring during the first night and incorporates the z band from the second night onward. This strategy improves the identification precision by exploiting the increasingly prominent red excess produced by the kilonova. Our results provide a physical basis for optimizing WFST observing resources to efficiently detect and characterize kilonovae in the multimessenger era.
ER -