TITLE: GCN CIRCULAR NUMBER: 44968 SUBJECT: Konus-Wind detection of GRB 260616B/EP260616a DATE: 26/06/17 15:37:56 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 260616B (BALROG localization: Preis & Greiner, GCN 44951; Fermi-GBM detection: Malacaria et al., GCN 44953; EP-WXT detection: Li et al., GCN 44956; CALET-GBM detection: Asaoka et al., GCN 44966) triggered Konus-Wind at T0=25522.793 s UT (07:05:22.793). The burst light curve shows two multi-peaked emission pulses. The total duration of the burst is ~13 s. 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/GRB260616_T25522/ As observed by Konus-Wind, the burst had the total fluence of 2.52(-0.29,+0.30)x10^-5 erg/cm2, and the 64-ms peak flux, measured from T0+9.760 s, of 8.62(-1.09,+1.12)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+16.832 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(-0.18,+0.23), the high energy photon index beta = -2.25(-0.28,+0.16), the peak energy Ep = 279(-49,+62) keV (chi2 = 101/97 dof). The spectrum near the maximum count rate (measured from T0+8.640 to T0+16.832 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.05(-0.10,+0.11) and Ep = 382(-41,+52) keV (chi2 = 87/85 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.0 (chi2 = 87/84 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/44968. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...