TITLE: GCN CIRCULAR NUMBER: 32591 SUBJECT: Ultra-long GRB 220525B: Konus-Wind and Fermi-GBM detection DATE: 22/09/26 21:01:55 GMT FROM: Dmitry Svinkin at Ioffe Institute svinkin@mail.ioffe.ru
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.