TITLE:   GCN CIRCULAR
NUMBER:  40110
SUBJECT: GRB 250407A: SRG/ART-XC afterglow detection
DATE:    25/04/07 19:48:18 GMT
FROM:    Sergey Molkov <serge.molkov@gmail.com>

S. Molkov, A. Tkachenko, I. Mereminskiy, A. Semena, A. Lutovinov,
I. Lapshov, V. Arefiev, A. Shtykovskiy and D. Karasev
on behalf of the ART-XC team (IKI Moscow) report:


During the ongoing all sky survey the Mikhail Pavlinsky ART-XC telescope
passed through the localization area of GRB250407A (GCN 40104,
GCN 40105) and detected a new X-ray source with coordinates:
(RA,Dec)=(110.7564,36.7979) J2000; the 1 sigma statistical error radius is 20 arcsec.
The source was in the FoV of the ART-XC telescope during ~20 seconds
with a central time of 2025-04-07T17:08:20 UTC (on-board time),
approximately 90 minutes after the burst had been detected
by GBM (GCN 40104).

The mean flux during the transition was about 1.4e-10 ergs/s/cm2
in the 4-12 keV energy band.  We expect that it's an afterglow detection
of GRB 250407A.

Urgent Swift/XRT follow-up observation was requested to obtain
precise localization.