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.