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GCN Circular 35059

GRB 231115A: GBM/Fermi Observations of a probable Giant Flare of Magnetar
2023-11-16T09:52:35Z (6 months ago)
Alexei Pozanenko at IKI, Moscow <>
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P. Minaev (IKI), A. Pozanenko (IKI) report on behalf of GRB IKI FuN:

We analyzed GRB 231115A, detected till now by GBM/Fermi (GCN 35035, GCN 35044) and INTEGRAL (GCN 35037), Glowbug (GCN 35045), using publicly available data of GBM/Fermi. The light curve of the burst is FRED-like with duration of T_90 = 0.06 +/- 0.01 s in (7, 850) keV energy range. The spectral analysis in a time interval of (-0.05, 0.05) s since GBM trigger, the best fit is obtained for CPL model with following parameters: E_p = 613 (- 60, +74) keV, alpha = 0.33 +/- 0.21. The fluence of F = (7.2 +/- 0.5)E-7 erg/cm**2 is obtained in 10 - 1000 keV energy band, Eiso = (1.24 +/- 0.14)E45 erg in (1, 10000) keV energy range for D_L = 3.5 Mpc of M82. Using Ep,i – Eiso correlation and T_90,i - EH diagram [1,2] we classify the burst as the SGR giant flare. Taking into account the non-detection of gravitational waves with LIGO/Virgo/KAGRA (LIGO Scientific Collaboration, Virgo Collaboration, KAGRA Collaboration, GCN 35049) we can suggest the GRB 231115A as the giant flash of a new SG!
 R in M82 galaxy.

Ep,i – Eiso correlation can be found at

T_90,i - EH diagram can be found at

[1] - Minaev et al., MNRAS, 492, 1919, 2020 
[2] - Minaev et al., Astronomy Letters, 46, 9, 573, 2020

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