TITLE: GCN CIRCULAR NUMBER: 39375 SUBJECT: Konus-Wind detection of GRB 250215A / EP250215a DATE: 25/02/19 15:45:03 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 250215A / EP250215a (Fermi-GBM detection: The Fermi GBM team, GCN 39327; Scotton and Meegan, GCN 39342; EP-WXT detection: Wang et al., GCN 39329; INTEGRAL-SPI-ACS detection: Barria et al., GCN 39331; AstroSat-CZTI detection: Tembhurnikar et al., GCN 39334; SVOM/GRM detection: Zheng et al., GCN 39335) triggered Konus-Wind at T0=09130.387 s UT (02:32:10.387). The burst light curve shows a multipeaked structure which starts at ~T0-14 s and has a total duration of ~22 s. The emission is seen up to ~1 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250215_T09130/ As observed by Konus-Wind, the burst had a fluence of 8.33(-1.97,+2.51)x10^-6 erg/cm2, and a 64-ms peak flux, measured from T0+0.054 s, of 5.12(-1.37,+1.66)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). Since a major part of the burst emission was detected before the trigger time and the burst shows a minor spectral evolution, we use the spectrum measured from T0 to T0+8.448 s to estimate the total burst fluence. This spectrum is best fit in the 20 keV - 20 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.03(-0.54,+0.69), the high energy photon index beta = -2.31(-1.22,+0.30), the peak energy Ep = 130(-36,+80) keV (chi2 = 80/97 dof). The spectrum near the maximum count rate (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 4 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.14(-0.74,+3.47), the high energy photon index beta = -2.35(-0.68,+0.29), the peak energy Ep = 118(-51,+53) keV (chi2 = 18/17 dof). Assuming the redshift z=4.61 (Sanchez-Ramirez et al., GCN 39343) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the following rest-frame parameters: the isotropic energy release E_iso is 3.35(-0.79,+1.01)x10^53 erg, the peak luminosity L_iso is 1.15(-0.31,+0.37)x10^54 erg/s, the rest-frame peak energy of the time-averaged spectrum Ep,i,z is 660(-250,+298) keV. With the obtained estimates, GRB 250215A is inside 68% prediction band for the 'Amati' and 90% - for the 'Yonetoku' relations derived for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250215_T09130/GRB250215A_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/39375. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...