TITLE: GCN CIRCULAR NUMBER: 36809 SUBJECT: Konus-Wind detection of GRB 240703A (a counterpart of EP240703a) DATE: 24/07/03 13:48:13 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: A long-duration GRB 240703A was detected by Konus-Wind (KW) in the waiting mode at ~00:38:32 UT. The burst source is located in the southern ecliptic hemisphere. Corrected for the propagation time, the burst was detected ~2 s before the start time of the fast X-ray transient EP240703a (T0=T0(EP)=00:38:40 UT; Wang et al., GCN 36807). The positional and temporal coincidence of this burst with the EP transient supports the conclusion that EP240315a is the GRB counterpart. A Bayesian block analysis of the KW waiting mode data in the 20-1250 keV band reveals a >12 sigma count rate increase in the interval from T0-2 s to T0+136 s. The burst light curve shows a multi-peaked structure with the brightest peak around ~T0+13 s. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB240703A/ The time-integrated spectrum of the burst, measured from T0-2 s to T0+136 s, is best described by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.09(-0.30,+0.47) and Ep = 180(-44,+62) keV. The spectrum near the peak count rate, measured from T0-2 s to T0+33 s, can be described by a CPL model with alpha = -0.75(-0.33,+0.41) and Ep = 276(-58,+81) keV. The total burst fluence is 1.36(-0.18,+0.18)x10^-5 erg/cm^2, and the 2.944 s peak energy flux, measured from T0+12.5 s, is 2.8(-0.4,+0.4)x10^-7 erg/cm^2. (both in the 20 keV - 10 MeV energy range). 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/36809. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...