TITLE:   GCN CIRCULAR
NUMBER:  41013
SUBJECT: GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
DATE:    25/07/07 17:17:34 GMT
FROM:    Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>

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

The long-duration GRB 250706C triggered Konus-Wind (KW)
at T0=60322.626 s UT (16:45:22.626).

The burst light curve shows a very bright, multi-peaked
emission pulse with the duration of ~50 s (20-1500 keV).
This pulse is followed by a weaker, smoothly decaying emission tail,
visible at lower energies (20-100 keV) up to the end
of the KW triggered data record (~T0+250 s).

A preliminary plot of the KW light curve is available at
http://www.ioffe.ru/LEA/GRBs/GRB250706_T60322/KW20250706_60322_BG.png

The KW ecliptic latitude response suggest the source location
in the southern ecliptic hemisphere, at moderate-to-high ecliptic latitude.

We note that the KW trigger time is ~1200 s before SVOM/ECLAIRs trigger
on GRB 250706B at 2025-07-06T17:05:23 (Palmerio et al., GCN 40989),
in the [5-20] keV energy band, and localized to R.A., Dec. 41.1337, -50.1172 deg,
which is consistent with the KW ecliptic latitude response.

This may suggest that the KW GRB 250706C is an initial, prompt emission
episode of GRB 250706B.

The KW analysis of GRB 250706C is ongoing and its detailed results will
be reported in a separate GCN.