GCN Circular 37872
Subject
EP241025a (GRB 241025A): EP observations update
Date
2024-10-25T10:20:16Z (3 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
D. Y. Li (NAO, CAS), Z. Y. Liu, M. Q. Huang (USTC), J. Q. Peng (IHEP, CAS), C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team:
The preliminary analysis of the telemetry EP-WXT data shows that the bright transient EP241025a (GRB 241025A, Swift GCN 37859, Fermi GBM GCN 37860, SVOM/GRM GCN 37863, EP GCN 37864) began at (T0) 2024-10-25T01:35:29 (UTC), and lasted for around 300 seconds, with the peak flux in 0.5-4.0 keV to be around 1e-8 erg/s/cm2. The EP-FXT autonomous observation began at T0+3min and caught the latter half of the bright transient, followed by lasting fainter emission. The ground calculated EP-FXT position is RA=333.6550 deg, DEC=83.5750 deg (J2000), with an uncertainty of 10 arcsecs (radius, 90% C.L. statistical and systematic), which is consistent with the enhanced XRT position (GCN 37868). The averaged EP-FXT spectrum can be fitted with an absorbed powerlaw, with a photon index of (1.41 +/- 0.09), and an absorption of NH= (2.2 +/- 0.4) e21 cm^(-2). The derived average unabsorbed flux in 0.5-4.0 keV is (1.6 +/- 0.7) e-10 erg/s/cm2. All the errors of the parameters quoted are at 90% C.L.
Please note that the temporal and spectral analyses presented above are preliminary. The final results will be presented in future publications. EP-FXT will also keep monitoring this transient in the following days.
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).