TITLE: GCN CIRCULAR NUMBER: 45196 SUBJECT: Konus-Wind detection of GRB 260721A DATE: 26/07/22 14:58:58 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, V. Panteleeva, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 260721A (NuSTAR-ACS detection: Grefenstette and Waratkar, GCN 45192) triggered Konus-Wind at T0=04620.710 s UT (01:17:00.710). The burst light curve shows a single pulse which starts at ~T0-0.6 s and has a total duration of ~33 s (75-1200 keV). The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260721_T04620/ As observed by Konus-Wind, the burst had the total fluence of 2.03(-0.14,+0.18)x10^-5 erg/cm2, and the 64-ms peak flux, measured from T0+1.568 s, of 2.41(-0.44,+0.45)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+33.024 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 = -0.48(-0.11,+0.14), the high energy photon index beta = -2.69(-0.22,+0.19), the peak energy Ep = 161(-11,+10) keV (chi2 = 93/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+8.448 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 = 0.02(-0.15,+0.17), the high energy photon index beta = -2.76(-0.27,+0.18), the peak energy Ep = 196(-12,+13) keV (chi2 = 84/82 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/45196. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...