GCN Circular 41184
Subject
GRB 250727A: AST3-2 Upper limit
Event
Date
2025-07-28T10:02:21Z (2 months ago)
From
Tianrui Sun at Purple Mountain Obs,CAS <trsun@pmo.ac.cn>
Via
Web form
Tian-Rui Sun, Yan-Long Hua (Purple Mountain Observatory, CAS), Kun Ma, Jiali Chen, Kai-wen Zheng, Yi-Qiao Yang, Xiao-Yan Li(Nanjing Institute of Astronomical Optics & Technology, CAS), Jin-Jun Geng, Wenlong Zhang, Xue-Feng Wu (Purple Mountain Observatory, CAS), report on behalf of the AST3 Team:
Following the detection of GRB 250727A by ECLAIRs onboard SVOM (Cao et al., GCN 41176),
we carried out follow-up observations using the Antarctic Survey Telescope AST3-2 located at Dome A, Antarctica (Lat. −80.4173°, Long. 77.0950°).
Observations began at 2025-07-27T11:09:43.449 UT.
No significant optical counterpart was detected within the ECLAIRs error circle (~9 arcmin radius), compared to the Gaia DR2 catalog. The stacked image (71 × 30 s exposures) in the i-band reached a 5σ limiting magnitude of ~18.9. This non-detection is consistent with the non-detection reported by SVOM/VT (Li et al., GCN 41181).
Photometric calibration was performed using the ATLAS Reference Catalog (Tonry et al. 2018).
We thank Prof. Michael Ashley (UNSW) for his continuous support in the operation of AST3-2.