GCN Circular 32591

D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova,
A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team

and

A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,
report:

The ultra-long GRB 220525B was initially found in
the Konus-Wind (KW) waiting mode data.

As observed by Konus-Wind the source of the burst
is in the southern ecliptic hemisphere
at ecliptic latitude of -32 +/- 22 deg (3 sigma).

A Bayesian block analysis of the KW waiting mode data in
the 20-1600 keV band reveals a 30 sigma count rate increase
over background in the interval from 13447 s UT (03:44:07),
hereafter T0, to 18763 s UT (05:12:43; T0 + 5316 s).
The burst lightcurve shows a single smooth pulse peaking at ~T0+600 s.

The Konus-Wind lightcurve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB220525B/

As observed by Konus-Wind, the burst had a fluence of
1.94(-0.11,+0.13)x10^-4 erg/cm2 and a 2.944-s peak flux,
measured from ~T0+521 s, of 3.55(-0.77,+0.78)x10^-7 erg/cm2/s
(both in the 20 - 1500 keV energy band).

The KW 3-channel time-integrated spectrum
(from T0 to T0 + 3147 s)
can be described by a cutoff power-law model
with alpha = -0.24(-0.14,+0.15) and Ep = 478(-33,+48) keV.

All the quoted KW errors are estimated at the 1 sigma confidence level.

The Fermi-GBM Earth Occultation Technique was run over positions
covering the Konus-Wind ecliptic band, identifying a setting step of
a bright, uncatalogued source. The region that becomes occulted by Earth
for Fermi during the step time is weighted by the Konus-Wind ecliptic
band to generate the HEALPix map available at the Konus summary link.