TITLE: GCN CIRCULAR NUMBER: 44806 SUBJECT: Konus-Wind detection of GRB 260601B/EP260601a DATE: 26/06/03 16:14:45 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 260601B (GECAM-B detection: Yu et al., GCN 44767; Wang et al., GCN 44768; NuSTAR detection: Waratkar et al., GCN 44771; CALET-GBM detection: Sugita et al., GCN 44773; Insight-HXMT detection: Wang et al., GCN 44785; Glowbug detection: Cheung et al., GCN 44801) triggered Konus-Wind at T0=69173.304 s UT (19:12:53.304). The burst light curve shows a multipeaked structure which starts at ~T0-3.2 s and has a total duration of ~230 s. The emission is seen up to ~8 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260601_T69173/ As observed by Konus-Wind, the burst had the total fluence of 3.34(-0.17,+0.17)x10^-4 erg/cm2, and the 64-ms peak flux, measured from T0+27.552 s, of 1.66(-0.19,+0.19)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+210.688 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 = -0.79(-0.10,+0.12), the high energy photon index beta = -1.74(-0.05,+0.04), the peak energy Ep = 441(-68,+82) keV (chi2 = 125/97 dof). The 'peak-flux' spectrum (measured from T0+24.832 to T0+31.232 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 = -0.89(-0.07,+0.07), the high energy photon index beta = -1.82(-0.06,+0.05), the peak energy Ep = 671(-98,+117) keV (chi2 = 108/82 dof). Assuming a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimated the burst isotropic energy release E_iso, the isotropic peak luminosity L_iso, and the rest-frame peak spectral energy Ep,z of the burst at different redshifts. With the obtained estimates GRB 260601B is consistent with the 68% prediction band of the 'Amati' relation for z >~0.2 and with the 68% prediction band of the 'Yonetoku' relation for z>~1.0 (see http://www.ioffe.ru/LEA/GRBs/GRB260601_T69173/GRB260601B_rest_frame.pdf) 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/44806. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...