TITLE:   GCN CIRCULAR
NUMBER:  37824
SUBJECT: GRB241018A: XingLong Optical Upper Limit
DATE:    24/10/19 12:04:59 GMT
FROM:    Fei-Fan Song at Yunnan Observatories <songfeifan@ynao.ac.cn>

F.-F. Song (YNAO), X.-H. Han, L.-P. Xin, J. Wang, H.-L. Li, C. Wu (NAOC), R.-Z. Li, B.-T. Wang, J. Mao (YNAO), Y.-L. Qiu, J.-Y. Wei (NAOC), E.-W. Liang, X.-G. Wang (GXU), H. Gao (BNU), J.-J. Jie and J. Zheng (NAOC)  report on behalf of a large collaboration:

We observed the field of GRB241018A (Atteia et al., GCN 37812, T0 at 2024-10-18T11:54:34 UT) using the Xinglong-2.16m telescope. The observation began at 2024-10-18T14:50:59, about 2.93 hours after the trigger.

No new uncataloged optical source was detected within the SOVM-ECLAIRs error circle (GCN 37812).

The preliminary analysis results are shown as follows:
+----------------+------------+----------+----------------+
|  Tmid-T0 [hr]  |  Exp. [s]  |  Filter  |  5-sigma U.L.  |
+================+============+==========+================+
|      2.97      |    300     |    R     |      19.09     |
+----------------+------------+----------+----------------+

The given magnitudes are derived based on calibrating against Pan-STARRS1 field stars.