GCN Circular 40919
Subject
GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
Event
Date
2025-07-03T15:14:48Z (a day ago)
From
Jamie Kennea at Penn State <jak51@psu.edu>
Via
Web form
J. A. Kennea, M. H. Siegel (PSU), P. A. Evans, K. L. Page (Leicester) and B. O'Connor (CMU) report on behalf of the Swift Team:
Swift began an TOO observation of the Einstein Probe (GCN #40906) of this source that showed repeated outbursts detected by Fermi/GBM (GCN #40883, #40885, #40886, #40890, #40891) and Swift/BAT-GUANO (GCN #40903) on July 3, 2025 at 01:34UT. We detect a bright uncatalogued X-ray point source at the following localization: RA/Dec(J2000) = 284.69006, -7.87413 which is equivalent to:
RA(J2000) = 18h 58m 45.61s,
Dec(J2000) = -07d 52' 26.9'',
with an estimated error uncertainty of 2.0 arc-seconds radius (90% confidence). This position is not coincident with any UVOT detected source. The X-ray flux during the Swift TOO observation is highly variable, showing a rapid fading behavior during the first orbit of data, suggesting the tail end of a flare, with the average rate over the orbit of 1.5 +/- 0.1 c/s. Following orbits the source has count rate between of 0.4-0.5 c/s.
The spectrum is well fit by an absorbed power law with N_H = 1.1 +/- 0.2 x 10^22 cm^-2, and a photon index of 1.65 +/- 0.20. The average flux of the source is 4.5 +/- 0.4 10^-11 erg/s/cm^2 (0.3-10 keV) observed, and 6.8 (+0.9/-0.6) x 10^-11 erg/s/cm^2 (0.3 - 10 keV) corrected for absorption.
Further Swift observations of this object are planned. Follow-up observations to classify the source are highly encouraged.