TITLE:   GCN CIRCULAR
NUMBER:  37985
SUBJECT: GRB 241030B: Nanshan/HMT optical afterglow detection
DATE:    24/10/30 19:17:38 GMT
FROM:    Dong Xu at NAOC/CAS <dxu@nao.cas.cn>

S.Y. Fu, S.Q. Jiang, J. An, X. Liu, Z.P. Zhu, D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report on behalf of a large collaboration:

We observed the field of GRB 241030B detected by Fermi/GBM (Fermi GBM team, GCN 37980), Swift/BAT (Klingler et al., GCN 37981), and SVOM/ECLAIRs (Zhao et al., GCN 37984), using the HMT-0.5m telescope located at Nanshan, Xinjiang, China. Observations started at 18:36:30 UT on 2024-10-30, i.e., 2.17 mins after the Swift trigger, and a series of 20 s, 40 s , 60 s, 120 s frames have been obtained without any filter. 

An uncatalogued and varying optical transient (OT) is detected in our images, being consistent with the enhanced XRT position (Evans et al., GCN 37983), at coordinates (J2000)

R.A. = 3:23:10.26
Dec. = +34:26:49.98

with an uncertainty of ~ 0.5 arcsec. The OT has R ~ 19.1 mag at 8.17 mins post-trigger, calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction.

Observations are ongoing.