TITLE:   GCN CIRCULAR
NUMBER:  37347
SUBJECT:  GRB 240828B: SVOM/C-GFT optical upper limit
DATE:    24/08/30 02:28:00 GMT
FROM:    Chao Wu at NAOC <cwu@nao.cas.cn>

SVOM/C-GFT team: Chao WU (NAOC), Zhe Kang (CHO)，Liping Xin(NAOC), Xuhui Han(NAOC),Pinpin Zhang (NAOC)，Xiaomeng Lu (NAOC), Zhenwei Li (CHO)，You Lv (CHO)，Ruosong Zhang (NAOC)，Yujie Xiao(NAOC)

SVOM JSWG: Jian-Yan Wei (NAOC,  China), Bertrand Cordier (CEA, F), Shuang-Nan Zhang (IHEP, CN), Stephane  Basa (LAM, F), Jean-Luc Attéia (IRAP, F), Arnaud Claret (CEA, F),  Zi-Gao Dai (USTC, CN), Frederic Daigne (IAP, F), Jin-Song Deng (NAOC, CN), Andrea Goldwurm (APC, F), Diego  Götz (CEA, F), Xu-Hui Han (NAOC, CN), Cyril Lachaud (APC, F), En-Wei Liang (GXU, CN), Yu-Lei Qiu (NAOC, CN), Susanna Vergani (Obs.Paris, F), Jing Wang (NAOC, CN), Chao Wu(NAOC, CN), Li-Ping Xin (NAOC,CN), Bing Zhang (UNLV, CN)

We observed the field of the SVOM/ECLAIRs-detected burst GRB 240828B (Le Provost et al., GCN 37318) starting at 16:14:47 UT, August 28, 2024, ~3.06 hr after the burst trigger with C-GFT (Chinese Ground Follow-up Telescope in SVOM mission) in System Test Mode (STM). C-GFT is located at Jilin (long.=126.33 deg, lat.= 43.8243778 deg), Changchun Observatory, National Astronomical Observatories, CAS. It has FOV of 1.28 deg x 1.28 deg with a 4k*4k CMOS detector mounted on the primary focus of 1.2-meter-aperure telescope.

A series of g ,r, and i band images were obtained. We obtained stacked images of g: 249x10s, r: 232x 10s and i: 244x10s. No optical counterpart candidate was detected within the X-ray afterglow error
circles (Page et al. GCN 37334) down to the limiting magnitude of mag_g=19.7, mag_r=19.2, and
mag_i=20.1 . It is consistent with the results reported by Zheng et al.(GCN 37345) and Moskvitin et al. (GCN 37346). 

The photometry was calibrated with nearby Pan-STARRS 1 catalogs.

We thank the observation assistant Chunlei Guo at Jilin observatory for their excellent support.