TITLE:   GCN CIRCULAR
NUMBER:  37217
SUBJECT: GRB 240819A: JinShan optical upper limits on one Swift/XRT source
DATE:    24/08/21 15:22:52 GMT
FROM:    Dong Xu at NAOC/CAS <dxu@nao.cas.cn>

S.Q. Jiang, Z.P. Zhu, X. Liu, J. An, S.Y. Fu, D. Xu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration:

We observed the Swift/XRT Source 1 (Evans et al., GCN37203), an X-ray afterglow candidate of GRB 240819A detected by SVOM/Eclairs (Coleiro et al., GCN 37208), using the 100C telescope of the JinShan project located at Altay, Xinjiang, China. Observations started at 20:16:17.46 UTC on 2024-08-20, i.e., 1.737 day after the T0 of this GRB, and a series of frames were obtained in the Sloan i- and z- bands.

No new optical source is detected within the Swift/XRT Source 1 error circle, down to the following 3-sigma optical upper limits:

-----------------------------------------------------------------
Tmid-T0(hr)  exp(s)   filter      UL(3-sigma)
-----------------------------------------------------------------
41.974        14x120      i           >20.6
42.663        22x120      z           >20.3
-----------------------------------------------------------------

calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction.

We acknowledge the excellent support from S.W. Luo, Z.K. Feng, Q.C. Zhao, M.M. Yang, and L.F. Huo for enabling these observations.