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Main 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
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2501.17506
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author 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
author_facet 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
contents 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.
format Preprint
id arxiv_https___arxiv_org_abs_2501_17506
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle GECKO Follow-up Observation of the Binary Neutron Star-Black Hole Merger Candidate S230518h
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
High Energy Astrophysical Phenomena
Instrumentation and Methods for Astrophysics
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.
title GECKO Follow-up Observation of the Binary Neutron Star-Black Hole Merger Candidate S230518h
topic High Energy Astrophysical Phenomena
Instrumentation and Methods for Astrophysics
url https://arxiv.org/abs/2501.17506