GCN Circular 37245
Subject
GRB 240821A: JinShan optical upper limits
Date
2024-08-23T12:04:05Z (9 months ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
S.Q. Jiang, J. An, Z.P. Zhu, X. Liu, S.Y. Fu, D. Xu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration:
We observed the field of GRB 240821A detected by Fermi (GCN 37219 & GCN 37239), SVOM (GCN 37220 & GCN 37226), and EIRSAT-1 (GCN 37232), using the 100cm-C telescope (100C) located at Altay, Xinjiang, China. Observations started at 18:43:03.73 UTC on 2024-08-22, i.e., 24.12 hr after the Fermi trigger, and a series of frames were obtained in the Sloan i- and z- bands.
No new optical source is detected within the EP/FXT (Turpin et al., GCN 37230) and Swift/XRT (Evans et al., GCN37236) error circles, down to the following 3-sigma optical upper limits:
Source | R.A. | Dec. | Mag_i | Mag_z
------------------------------------------------------------
EP J233704.9-101126 | 354.2703 | -10.1905 | >20.0 | >19.4
EP J233641.3-100257* | 354.1720 | -10.0491 | >20.2 | >19.4
EP J233641.6-101036 | 354.1735 | -10.1767 | >20.2 | >19.4
EP J233642.1-101318 | 354.1754 | -10.2217 | >20.2 | >19.4
EP J233708.1-101515 | 354.2836 | -10.2542 | >20.0 | >19.4
EP J233710.3-100324+ | 354.2929 | -10.0566 | >20.0 | >19.4
EP J233727.8-100744 | 354.3657 | -10.1290 | >20.0 | >19.4
EP J233636.5-100302 | 354.1522 | -10.0507 | >20.2 | >19.4
XRT Source1+ | 354.28992 | -10.05366 | >20.0 | >19.4
XRT Source2* | 354.17265 | -10.04975 | >20.2 | >19.4
calibrated with nearby PanSTARRS stars and the magnitudes are not corrected for Galactic extinction. The sources marked with the same symbol (i.e., * and +) are very likely an identical one detected by both EP/FXT and Swift/XRT.
We acknowledge the excellent support from S.W. Luo, Z.K. Feng, M.M. Yang, and L.F. Huo for enabling these observations.