TITLE:   GCN CIRCULAR
NUMBER:  33283
SUBJECT: GRB 230205A: SVOM/C-GFT optical upper limit
DATE:    23/02/06 13:09:38 GMT
FROM:    Chao Wu at NAOC  <wuchao.lamost@gmail.com>

Chao Wu (NAOC),  Zhe Kang (CHO), Liping Xin (NAOC), Xuhui Han (NAOC),
Xiaomeng Lu (NAOC),  Damien Turpin(CEA),  Zhenwei Li (CHO)，Pinpin
Zhang (NAOC)，Ruosong Zhang (NAOC)，Yulei Qiu (NAOC)，You  Lv (CHO)，Jing
Wang(GXU), Cordier Bertrand (CEA)  and Jianyan Wei (NAOC) on behalf of
SVOM GRB team

We observed the burst GRB230205A (Ambrosi et al. GCN 33271) on
14:02:03 UT, Feb. 5th, 2023, about 3.5 hours after the Swift 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 1.5 deg X 1.5 deg with a 4k*4k CMOS
detector mounted on the primary focus of  1.2-meter-aperure telescope.

A series of g and r band images were obtained. The exposure time was
30 seconds for each frame.

No optical afterglow was detected within the enhanced XRT error box
(Goad et al., GCN 33275) down to a limit magnitude of 17.0 mag in each
r-band single frame (in STM).  The photometry was calibrated with
nearby UCAC 4 catalogs. The upper limit is consistent with the limit
reports (Ambrosi et al. GCN 33271;  Hu et al., GCN 33274).

More detailed analysis is continuing.

We thank the observation assistant Bowen Li at Jilin observatory for
their excellent support.