TITLE: GCN CIRCULAR NUMBER: 39095 SUBJECT: GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading DATE: 25/01/30 09:08:18 GMT FROM: Damien Turpin at CEA-Saclay dturpin-astro@hotmail.com
Y.-H. I. Yin (NJU), Y. L. Wang, H. N. Yang, H. Y. Liu (NAO, CAS), Z. Y. Liu, M. Q. Huang (USTC), Z. X. Ling, Y. Liu (NAO, CAS), B. Cordier, D. Turpin (CEA) on behalf of the Einstein Probe team:
We performed a second follow-up observation of GRB 250127A (SVOM, Wu et al., GCN 39041) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started at 2025-01-29 09:55:45 (UTC) with ~ 4.9 ks of exposure in total.
The uncatalogued x-ray source detected by both Swift/XRT (Source 2, Kennea et al., GCN 39056) and EP-FXT (Yin et al. GCN 39053) is no longer detected in our second EP-FXT epoch. Assuming Galactic equivalent hydrogen column density of 4.52 x 10^20 cm^-2 and a photon index of 2.0, the upper limit of the 0.5-10 keV flux is estimated to be 1.93 x 10^-14 erg/s/cm^2. The fading behavior of the x-ray source identified by Yin et al. GCN 39053 and Kennea et al., GCN 39056, confirms it as being the afterglow of GRB 250127A.
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.
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