GCN Circular 39804
Subject
EP250321a: TRT optical counterpart detection
Date
2025-03-21T08:39:06Z (5 days ago)
From
sqjiang at NAOC <sqjiang@bao.ac.cn>
Via
Web form
S.Y. Fu (HUST), W.X. Li, J. An, S.Q. Jiang (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), X. Liu, Z.P. Zhu, Z. Fan, N.C. Sun, D. Xu, Y.N. Wang (NAOC) report on behalf of a large collaboration:
We observed the field of EP250321a detected by EP/WXT (Hu et al., GCN 39800) using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Sierra Remote Observatories in California. We obtained several 300 s frames in the R and I filters.
An uncatalogued and decaying optical source is detected within the error circle at coordinates
R.A. (J2000) = 11:57:03.02
Dec. (J2000) = +17:21:45.94
with an uncertainty of ~0.5 arcsec. The source has R ~ 19.7 mag at 1.24 hr and I ~ 18.8 mag at 1.72 hr after the EP trigger, calibrated with nearby Pan-STARRS DR2 stars and not corrected for Galactic extinction.
We think that the source is very likely the optical counterpart of EP250321a.