TITLE: GCN CIRCULAR NUMBER: 36768 SUBJECT: Konus-Wind detection of GRB 240619A DATE: 24/06/26 21:43:33 GMT FROM: Dmitry Svinkin at Ioffe Institute svinkin@mail.ioffe.ru
D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 240619A (Fermi-GBM detection: The Fermi GBM team, GCN 36694; CALET-CGBM detection: Torii et al., GCN 36719; GRBAlpha detection: Dafcikova et al., GCN 36724; GOTO OT detection: Gompertz et al., GCN 36715; Swift-XRT afterglow detection: Capalbi et al., GCN 36721) triggered Konus-Wind at T0=13408.204 s UT (03:43:28.204).
The burst light curve shows two separated emission episodes. The initial harder episode starts at ~T0-0.2 s and has a total duration of ~14 s. The following softer episode starts at ~T0+22 s and ends at ~T0+36 s. The total burst duration is ~36 s. The emission is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB240619_T13408/
As observed by Konus-Wind, the burst had a fluence of 1.35(-0.36,+0.79)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+0.052 s, of 1.48(-0.50,+0.49)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+41.216 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 = -1.62(-0.21,+0.32) and Ep = 557(-300,+4475) keV (chi2 = 93/86 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -1.9 (chi2 = 93/85 dof).
The spectrum near the maximum count rate (measured from T0 to T0+0.256 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 = -0.60(-0.52,+0.86), the high energy photon index beta = -1.98(-8.02,+0.25), the peak energy Ep = 480(-218,+870) keV (chi2 = 29/40 dof).
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
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