TITLE: GCN CIRCULAR NUMBER: 40753 SUBJECT: Konus-Wind detection of GRB 250615A / EP250615a DATE: 25/06/17 11:35:08 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-duration GRB 250615A (Swift detection: Dichiara et al., GCN 40736; AstroSat CZTI detection: Tembhurnikar et al., GCN 40752), coincident with the X-ray transient EP250615a (Yang et al., GCN 40743), triggered Konus-Wind (KW) at T0=80722.429 s UT (22:25:22.429).
The burst light curve shows a multi-peaked emission pulse which starts at ~T0-5 s and has a total duration of ~50 s. The emission is seen up to ~4 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250615_T80722/
As observed by Konus-Wind, the burst had a fluence of (3.57 ± 0.50)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 5.248 s, of (5.32 ± 0.53)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+49.408 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 = -0.96 (-0.09,+0.11), the high energy photon index beta = -2.41 (-1.15,+0.35), the peak energy Ep = 908 (-187,+218) keV, chi2 = 84/97 dof.
The spectrum near the peak count rate(measured from T0 to T0+8.448 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 = -0.92 (-0.09,+0.09), the high energy photon index beta = -2.62 (-7.38,+0.41), the peak energy Ep = 1290 (-234,+320) keV, chi2 = 89/93 dof.
All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary.
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