GCN Circular 40607
Subject
GRB 250601A: EP-FXT follow-up observation and afterglow candidates
Date
2025-06-02T15:46:51Z (4 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Q. C. Liu (THU), X. Y. Zhou (PRIC), H. L. Peng (NNU), B. B. Zhang (BNU) and Y. Liu (NAO,CAS) report on behalf of the Einstein Probe (EP) team :
We performed a follow-up observation of GRB 250601A (detected through on-broad trigger of Fermi/GBM, Fermi, GCN #40596, and localized by Swift/BAT, DeLaunay, GCN #40600; followed by Swift/XRT, Page et al., GCN #40604), with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation began at 2025-06-02T02:10:26 (T-TGRB ~ 8.7 hrs) with an exposure time of about 5.8 ks.
Two uncatalogued sources were detected by FXT-A and FXT-B in the 3-sigma Swift/BAT error circle with a radius of 493 arcsecond centered at RA, DEC = 90.0709 deg, -57.2892 deg, as listed below (the FXT flux is taken from FXT-B module). EP J060023.3-571631 has a separation of 11.6 arcsecond from the XRT source 3, and EP J060048.7-571413 has a separation of 4.8 arcsecond from the XRT source 2.
Source name | RA | DEC | Estimated Flux | SNR | Dist from Swift/BAT |
| deg | deg | (erg/s/cm^2) | | offset (in arcmin) |
EP J060023.3-571631 | 90.0971 | -57.2752 | 3.2(+/-1.2) x 10^-14 | 4.1 | 1.19 |
EP J060048.7-571413 * | 90.2037 | -57.2368 | 1.0(+/-0.2) x 10^-13 | 9.4 | 5.33 |
Note: * EP J060048.7-571413 was also detected by Swift/XRT (GCN #40604) in a ~4.6 ks observation conducted at T-TGRB ~ 4.8 hrs, with a flux of ~ 4e-13 erg/s/cm^2. The source thus exhibits a decreasing trend in the X-ray flux within the two epochs.
The above observation was made with the EP-FXT instrument. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.