TITLE:   GCN CIRCULAR
NUMBER:  40460
SUBJECT: Konus-Wind detection of GRB 250512B / EP250512a
DATE:    25/05/15 11:03:14 GMT
FROM:    Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>

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

The long-duration GRB 250512B / EP250512a
(EP-WXT detection: Zhao et al., GCN 40437;
Yang et al., GCN 40448;
SVOM-ECLAIRs detection: Maggi et al., GCN 40439)
was detected by Konus-Wind (KW) in the waiting mode 
at about T0 = T0(EP) = 40803 s UT (11:20:03).

A Bayesian block analysis of the KW waiting mode data in
the 20-400 keV band reveals a ~8 sigma count-rate increase in
the interval from T0+7.4 s to T0+113.3 s.

The KW light curve of this burst is available
at http://www.ioffe.ru/LEA/GRBs/GRB250512B/

The total burst fluence is 6.68(-2.23,+1.59)x10^-6 erg/cm^2,
and the 2.944 s peak energy flux, measured from T0+10.309 s,
is 3.08(-1.14,+0.89)x10^-7 erg/cm^2.
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst,
measured from T0+7.4 s to T0+113.3 s,
can be described by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha > -1.82 and Ep = 114(-37,+57) keV.

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.