GCN Circular 43906
Subject
EP260302a: analysis of the follow-up EP-FXT observation
Event
Date
2026-03-03T11:54:52Z (3 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y. J. Zhang (THU), Y. H. Cheng, D. Zhu, K. J. Zhang (YNU), H. W. Pan (NAOC) on behalf of the Einstein Probe (EP) team:
The fast X-ray transient EP260302a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission at 2026-03-02T23:52:58 (UTC) (Zhang et al., GCN 43899), and was followed by several telescopes (Li et al., GCN 43898, Pérez-García et al., GCN 43903, Corcoran et al., GCN 43904). The X-ray source detected by WXT exhibited a flare within the first 100 seconds of the observation. The X-ray source detected by WXT has a 0.5--4 keV flux of approximately 1.4 x 10^-10 erg s^-1 cm^-2, with an power-law index of 1.1. The NH value is fixed to galactic value (8.6 x 10^20 cm^-2).
A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically, starting at 2026-03-02T23:54:17(UTC), about 2 minutes after the trigger. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 132.9717 deg, Dec. = -65.9839 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The uncatalogued X-ray source revealed a decline in its light curve during the FXT observation. Its X-ray spectrum has a 0.5–10 keV flux of 1.84(+0.05/-0.04) x 10^-10 erg s^-1 cm^-2, with a power-law index of 1.46(+0.04/-0.04) and a NH value of 8.6 x 10^20 (fixed galactic value) + 5.7 (+1.5/-1.4) x 10^20 cm^-2. All errors are performed with 90% significance.
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).