TITLE: GCN CIRCULAR NUMBER: 41109 SUBJECT: Konus-Wind detection of GRB 250716A DATE: 25/07/17 15:32:45 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 bright, long-duration GRB 250716A (Fermi-GBM detection: Fermi GBM team, GCN 41099; Mukherjee and Meegan, GCN 41102) triggered Konus-Wind at T0=5348.122 s UT (01:29:08.122).

The burst light curve shows a multipeaked structure which starts at ~T0-91 s and has a total duration of ~235 s. The emission is seen up to ~20 MeV.

The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250716_T05348/

As observed by Konus-Wind, the burst had a fluence of 2.39(-0.09,+0.09)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+2.544 s, of 4.26(-0.33,+0.33)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst (measured from T0 to T0+88.064 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.25(-0.04,+0.04), the high energy photon index beta = -1.78(-0.04,+0.03), the peak energy Ep = 554(-84,+93) keV (chi2 = 124/97 dof).

The spectrum near the maximum count rate (measured from T0+0.256 to T0+4.096 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.78(-0.06,+0.07), the high energy photon index beta = -1.59(-0.03,+0.03), the peak energy Ep = 726(-113,+139) keV (chi2 = 106/86 dof).

All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.

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