{
  "submittedHow": "web",
  "circularId": 45070,
  "eventId": "EP260703a",
  "format": "text/plain",
  "body": "R.-Z. Li (YNAO, CAS), G. L. Huang (IHEP, CAS), Z.-Y. Jian (HKU), X. Mao and Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team:\n\nWe report on the detection of a fast X-ray transient, designated EP260703a (notice ID: 11900792707), by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission . The transient was identified in the telemetry data. The transient started at 2026-07-03T03:13:57 (UTC) and lasted for about 50s, with a peak flux of ~ 2 x 10^(-9) erg cm^-2 s^-1 in 0.5-4 keV. The position of the transient is R.A. = 274.7265 deg, Dec. = -62.6004 (J2000), with an uncertainty radius of 2.7 arcmin in radius (90% confidence level, including both statistical and systematic uncertainties). There are no known X-ray sources in the WXT error circle.\n\nThe average WXT 0.5-4 keV spectrum can be fitted by an absorbed power-law model with a fixed Galactic hydrogen column density of 5.56×10^20 cm^-2 and a photon index of 0.22 (-1.17/+1.08). The derived average unabsorbed 0.5-4 keV flux is 1.46 (-0.81/+2.22) x 10^(-9) erg cm^-2 s^-1. The uncertainties are at the 90% confidence level for the above parameters.\n\nFollow-up observations by EP-FXT will be arranged.\n\nLaunched on 2024 January 9, Einstein Probe is a space-based X-ray observatory designed to monitor the dynamic X-ray sky and perform rapid follow-up observations of newly discovered transients (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).",
  "createdOn": 1783082687852,
  "submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
  "subject": "EP260703a: EP-WXT detection of a fast X-ray transient"
}