GCN Circular 40300

S.Q. Jiang, H.Y. Liu, R.D. Liang, H.W. Pan (NAO, CAS) on behalf of the Einstein Probe (EP) team:

EP-FXT performed a follow-up observation on SVOM/sb25043004 at 2025-04-30T17:26:25 (UTC), about 7 hours after the SVOM/ECLAIRs trigger (Liang et al. GCN # 40287). Two previously known X-ray sources and an uncatalogued X-ray source are detected within the ECLAIRs error circle.

Preliminary analysis on these source are automatically conducted, and details are listed as follows. 

Source 1: EPF_J180814.9-384246 (1eRASS J180815.0-384254) 
RA (J2000): 272.0610 
Dec (J2000): -38.7126
Flux: 1.77 x 10^-13 erg/cm^2/s (observed, 0.5-10 keV)
Flux_error: 3.7 x 10^-14 erg/cm^2/s (1 sigma)
Note: The source is spatially consistent with 1eRASS J180815.0-384254, which has a flux of 
8.34 (+4.22/-3.17, 1 sigma) x 10^-14 erg/cm^2/s (0.2-2.3 keV).

Source 2: EPF_J180840.1-384205 (1eRASS J180840.7-384211)
RA (J2000): 272.1683
Dec (J2000): -38.7025
Flux: 4.88 x 10^-13 erg/cm^2/s (observed, 0.5-10 keV)
Flux_error: 5.9 x 10^-14 erg/cm^2/s (1 sigma)
Note: The source is spatially consistent with 1eRASS J180840.7-384211, which has a flux of
1.41 (+0.52/-0.41, 1sigma) x 10^-13 erg/cm^2/s (0.2-2.3 keV).

Source 3: EPF_J180801.1-384501 (uncataloged)
RA (J2000): 272.0057
Dec (J2000): -38.7511
Flux:  2.44 x 10^-13 erg/cm^2/s (observed, 0.5-10 keV)
Flux_error: 4.6 x 10^-14 erg/cm^2/s (1 sigma)
Note: The upper limit given by eROSITA DR1 is 1.71 x 10^-13 erg/cm^2/s (0.2-2.3 keV).

The position uncertainties of the above 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).