TITLE: GCN CIRCULAR NUMBER: 38968 SUBJECT: Konus-Wind detection of GRB 250116A DATE: 25/01/17 13:56:46 GMT FROM: Anna Ridnaia at Ioffe Institute ridnaia@mail.ioffe.ru
A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The long-duration, bright GRB 250116A (Fermi/GBM detection: Bissaldi et al., GCN 38962; Fermi/LAT detection: Holzmann Airasca et al., GCN 38963; INTEGRAL/SPI-ACS and PICsIT detection: Barria et al., GCN 38965; GECAM-B detection: Wang et al., GCN 38967) triggered Konus-Wind at T0=45234.821 s UT (12:33:54.821).
The burst light curve shows a bright initial multipeaked emission episode which starts at ~T0-0.3 s and has a total duration of ~24.2 s, followed by a weaker emission traced up to ~175 s. The emission is seen up to ~3 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250116_T45234/
As observed by Konus-Wind, the initial emission episode had a fluence of 1.05(-0.03,+0.03)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+15.344 s, of 1.77(-0.14,+0.14)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the initial episode (measured from T0 to T0+26.112 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 = -0.58(-0.04,+0.04), the high energy photon index beta = -3.21(-0.28,+0.18), the peak energy Ep = 382(-10,+11) keV (chi2 = 111/98 dof).
A spectrum of the weaker emission tail (measured from T0+26.112 to T0+181.760 s) is best fit by a simple power-law (PL) function with the PL index of -2.13(-0.17,+0.19), chi2 = 97/100 dof. A 20 keV - 10 MeV fluence in this interval is estimated to 1.25(-0.29,+0.39)x10^-5 erg/cm2.
All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.
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