_version_ 1866917415227490304
author Liu, Zhengyan
Xu, Zelin
Jiang, Ji-an
Zhao, Wen
Jin, Zhiping
Dai, Zigao
Meng, Dezheng
Wu, Xuefeng
Wei, Daming
Liang, Runduo
He, Lei
Cai, Minxuan
Fan, Lulu
Wu, Weiyu
Zhao, Junhan
Jia, Ziqing
Yu, Kexin
Geng, Jinjun
Xiao, Di
Li, Feng
Tang, Jinlong
Zuo, Yingxi
Zhang, Xiaoling
Liu, Hao
Wang, Jian
Zhang, Hongfei
Liang, Ming
Wang, Hairen
Yao, Dazhi
Hu, Lei
Kong, Xu
Li, Bin
Jiang, Ning
Wang, Tinggui
Wan, Zhen
Xue, Yongquan
Zhu, Qingfeng
Zheng, Xianzhong
author_facet Liu, Zhengyan
Xu, Zelin
Jiang, Ji-an
Zhao, Wen
Jin, Zhiping
Dai, Zigao
Meng, Dezheng
Wu, Xuefeng
Wei, Daming
Liang, Runduo
He, Lei
Cai, Minxuan
Fan, Lulu
Wu, Weiyu
Zhao, Junhan
Jia, Ziqing
Yu, Kexin
Geng, Jinjun
Xiao, Di
Li, Feng
Tang, Jinlong
Zuo, Yingxi
Zhang, Xiaoling
Liu, Hao
Wang, Jian
Zhang, Hongfei
Liang, Ming
Wang, Hairen
Yao, Dazhi
Hu, Lei
Kong, Xu
Li, Bin
Jiang, Ning
Wang, Tinggui
Wan, Zhen
Xue, Yongquan
Zhu, Qingfeng
Zheng, Xianzhong
contents The gravitational wave (GW) event S250206dm, as the first well-localized neutron star merger candidate potentially located in the mass gap, presented a unique opportunity to probe the electromagnetic signatures from such a system. Here we report a deep, multiband search with the new 2.5-meter Wide Field Survey Telescope (WFST), covering about 64% of the localization region up to a 5-sigma limiting magnitude of 23 mag. In total, 12 potential candidates have been identified while none of them are likely related to S250206dm. This non-detection provides the most stringent constraint to date on any associated kilonova. Crucially, an AT 2017gfo-like event at 269 Mpc can be excluded by WFST observations alone. Based on ejecta mass limits, a neutron star-black hole with a large mass ratio (Q >= 3.2) is disfavored. This optical-derived constraint on the mass ratio reaches, for the first time, a precision comparable to that inferred from the GW signal. This work presents the best observation of this type of events until now, and demonstrates the power of rapid, deep follow-up observations to constrain the properties of compact binary progenitors, offering key insights into the constituents of the mass gap.
format Preprint
id arxiv_https___arxiv_org_abs_2602_17267
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Illuminating the Mass Gap Through Deep Optical Constraint on a Neutron Star Merger Candidate S250206dm
Liu, Zhengyan
Xu, Zelin
Jiang, Ji-an
Zhao, Wen
Jin, Zhiping
Dai, Zigao
Meng, Dezheng
Wu, Xuefeng
Wei, Daming
Liang, Runduo
He, Lei
Cai, Minxuan
Fan, Lulu
Wu, Weiyu
Zhao, Junhan
Jia, Ziqing
Yu, Kexin
Geng, Jinjun
Xiao, Di
Li, Feng
Tang, Jinlong
Zuo, Yingxi
Zhang, Xiaoling
Liu, Hao
Wang, Jian
Zhang, Hongfei
Liang, Ming
Wang, Hairen
Yao, Dazhi
Hu, Lei
Kong, Xu
Li, Bin
Jiang, Ning
Wang, Tinggui
Wan, Zhen
Xue, Yongquan
Zhu, Qingfeng
Zheng, Xianzhong
High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
The gravitational wave (GW) event S250206dm, as the first well-localized neutron star merger candidate potentially located in the mass gap, presented a unique opportunity to probe the electromagnetic signatures from such a system. Here we report a deep, multiband search with the new 2.5-meter Wide Field Survey Telescope (WFST), covering about 64% of the localization region up to a 5-sigma limiting magnitude of 23 mag. In total, 12 potential candidates have been identified while none of them are likely related to S250206dm. This non-detection provides the most stringent constraint to date on any associated kilonova. Crucially, an AT 2017gfo-like event at 269 Mpc can be excluded by WFST observations alone. Based on ejecta mass limits, a neutron star-black hole with a large mass ratio (Q >= 3.2) is disfavored. This optical-derived constraint on the mass ratio reaches, for the first time, a precision comparable to that inferred from the GW signal. This work presents the best observation of this type of events until now, and demonstrates the power of rapid, deep follow-up observations to constrain the properties of compact binary progenitors, offering key insights into the constituents of the mass gap.
title Illuminating the Mass Gap Through Deep Optical Constraint on a Neutron Star Merger Candidate S250206dm
topic High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2602.17267