GECKO Follow-up Observation of the Binary Neutron Star-Black Hole Merger Candidate S230518h
Year: 2025
Type: preprint
Abstract: The gravitational wave (GW) event S230518h is a potential binary neutron star-black hole merger (NSBH) event that was detected during engineering run 15 (ER15), which served as the commissioning period before the LIGO-Virgo-KAGRA (LVK) O4a observing run. Despite its low probability of producing detectable electromagnetic emissions, we performed extensive follow-up observations of this event using the GECKO telescopes in the southern hemisphere. Our observation covered 61.7\% of the 90\% credible region, a $\rm 284\:deg^2$ area accessible from the southern hemisphere, reaching a median limiting magnitude of $R=21.6$ mag. In these images, we conducted a systematic search for an optical counterpart of this event by combining a CNN-based classifier and human verification. We identified 128 transient candidates, but no significant optical counterpart was found that could have caused the GW signal. Furthermore, we provide feasible KN properties that are consistent with the upper limits of observation. Although no optical counterpart was found, our result demonstrates both GECKO's efficient wide-field follow-up capabilities and usefulness for constraining properties of kilonovae from NSBH mergers at distances of $\sim 200$ Mpc.
Source: arXiv (Cornell University)
Authors: Paek, Gregory S. H., Im, Myungshin, Jeong, Mankeun, Chang, Seo-Won, Hur, Martin Moonkuk, Hong, YoungPyo, Kim, Sophia, Lee, Jaewon, Lee, Dongjin, Lee, Seong-Heon, Jung, Jae-Hun, Kim, Joonho, Lee, Hyung Mok, Lee, Chung-Uk, Kim, Seung-Lee
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: Australian National Data Service, National Computational Infrastructure, Astronomy Australia Limited, Australian Government, Australian National University, National Research Foundation, Monash University, Swinburne University of Technology, Curtin University of Technology, Korea Astronomy and Space Science Institute, National Research Foundation of Korea, Ministry of Science and ICT, South Korea, Korea Research Environment Open Network, Australian Research Council, Australian Astronomical Optics-Macquarie, National Cancer Institute
OpenAlex ID: W4406975474