GCN Circular 40583
Subject
GRB 250530A: EP-FXT counterpart detection
Event
Date
2025-05-30T15:06:14Z (a month ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
D.Y. Li (NAO, CAS), Z. H. Yang, Q. C. Zhao (IHEP, CAS), J. Yang (NJU), H. W. Pan (NAO, CAS) on behalf of the Einstein Probe (EP) team:
EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 250530A (SVOM/sb25053002, Wang et al. GCN #40576) at 2025-05-30T07:26:04 (UTC), about 1 hour after the SVOM/ECLAIRs trigger, with an exposure time of 2970s. Three uncatalogued sources are detected within the ECLAIRs error circle, among which Source 1 is spatially consistent with the candidate counterpart detected by Swift/XRT (Evans et al. GCN #40579). Preliminary analysis on these source are automatically conducted, and details are listed as follows.
Source 1: EPF_J122650.7-023433
RA (J2000): 186.7114
Dec (J2000): -2.5759
Flux: 4.54 x 10^-12 erg/s/cm2 (observed, 0.5-10 kev)
Flux_err: 4.89 x 10^-13 erg/s/cm2 (1 sigma)
Note: This source is spatially consistent with the candidate counterpart detected by Swift/XRT, whose flux is (4.86 +/- 0.27) x 10^-11 erg/s/cm2 (0.3-10 keV).
Source 2: EPF_J122627.9-023807
RA (J2000): 186.6163
Dec (J2000): -2.6354
Flux: 6.31 x 10^-14 erg/s/cm2 (observed, 0.5-10 kev)
Flux_err: 1.94 x 10^-14 erg/s/cm2 (1 sigma)
Source 3: EPF_J122655.8-023705
RA (J2000): 186.7326
Dec (J2000): -2.5759
Flux: 1.33 x 10^-13 erg/s/cm2 (observed, 0.5-10 kev)
Flux_err: 2.74 x 10^-14 erg/s/cm2 (1 sigma)
The position uncertainty of the sources are about 10 arcsec in radius (90% C.L. statistical and systematic).
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).