TITLE: GCN CIRCULAR NUMBER: 40188 SUBJECT: GRB 250419A: JinShan optical observations DATE: 25/04/21 07:08:51 GMT FROM: sqjiang at NAOC sqjiang@bao.ac.cn
S.Q. Jiang (NAOC), S.Y. Fu (HUST), J. An, X. Liu, Z.P. Zhu, D. Xu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration:
We observed the field of GRB 250419A detected by SVOM/ECLAIRs (Wang et al., GCN 40168), using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 15:46:46.98 UT on 2025-04-20, i.e., 37.287 hr after the SVOM/ECLAIRs trigger, and a series of 600 s frames were obtained in the Sloan g-, r-, i- and z- bands.
The optical afterglow (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley et al., GCN 40181; Pankov et al., GCN 40182; Pérez-Fournon GCN 40183; Kuin et al., GCN 40185; WU et al., GCN 40186; Xie et al., GCN 40187), which is consistent with the X-ray observed result (Page et al., GCN 40173 and GCN 40176), of GRB 250419A is clearly detected in our stacked images. Preliminary photometry results are as follows:
T_mid(hr) Filter Mag(AB) MagErr 38.707 g 20.83 0.04 39.552 r 20.47 0.03 40.396 i 20.20 0.04 41.156 z 20.04 0.07
calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction.
We acknowledge the excellent support from T.Q. Chen and Z.K. Feng for enabling these observations.
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