TITLE: GCN CIRCULAR NUMBER: 35567 SUBJECT: Konus-Wind detection of GRB 240118A DATE: 24/01/18 18:44:56 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, very bright GRB 240118A (Fermi GBM observation: Hamburg et al., GCN 35563; Fermi LAT detection: Bissaldi et al., GCN 35560; NuSTAR detection: Grefenstette, GCN 35564) triggered Konus-Wind (KW) at T0=6508.107 s UT (01:48:28.107). The burst light curve shows a multi-peaked structure, which starts at ~T0-2.4 s, peaks at ~T0+37.5 s, and has a total duration of ~90 s. The emission is seen up to ~15 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB240118_T06508/ As observed by Konus-Wind, the burst had a fluence of (8.24 ± 0.38)x10^-4 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 37.568 s, of (6.65 ± 0.63)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+90.880 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.69 (-0.03,+0.03), the high energy photon index beta = -2.37 (-0.05,+0.05), the peak energy Ep = 402 (-12,+13) keV, chi2 = 167/97 dof. The spectrum near the peak count rate (measured from T0+36.352 s to T0+38.144 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.61 (-0.06,+0.07), the high energy photon index beta = -2.62 (-0.21,+0.15), the peak energy Ep = 634 (-51,+55) keV, chi2 = 74/66 dof. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/35567. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...