TITLE:   GCN CIRCULAR
NUMBER:  45368
SUBJECT: EP260812b: Einstein Probe detection of an X-ray transient
DATE:    26/08/13 02:29:37 GMT
FROM:    EP Team at NAOC/CAS <ep_ta@bao.ac.cn>

A. Li (BNU), G. L. Huang (IHEP), C. Y. Wang (THU) and W. D. Zhang (NAOC) on behalf of the Einstein Probe (EP) team:

We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260812b. The transient triggered EP-WXT (ID: 01709278129) at 2026-08-12T23:35:41 (UTC). The WXT position of the source is R.A. = 307.783 deg, DEC = -9.857 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).

A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 307.7920 deg, DEC = -9.8600 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). NOT also detected an possible optical counterpart 6.8 arcsec from FXT location (D. B. Malesani et al. 2026, GCN 45367).

Further information will be updated when the telemetry data is received.

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).