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GCN Circular 15025

Subject
GRB 130702A in the Ep,i - Eiso plane
Date
2013-07-23T13:50:35Z (11 years ago)
From
Lorenzo Amati at INAF-IASF/Bologna <amati@iasfbo.inaf.it>
L. Amati (INAF - IASF Bologna), S. Dichiara, F. Frontera, C. Guidorzi
(University of Ferrara), Luca Izzo (ICRANet, Rome), M. Della Valle
(INAF-Osservatorio Astronomico di Capodimonte) report:

A preliminary analysis of the spectral data of GRB130702A provided by the 
Fermi/GBM integrated over the whole duration of the event (63.3 s from 
T0-3.0 to T0 +60.3; detectors n7 and n8) suggests that the spectrum can be 
fit with a simple power-law with index ~2.1+/-0.1, which is significantly 
softer than the value obtained by considering only the brightest part of 
the event (Collazzi & Connaughton GCN 14972; Golenetskii et al. GCN 
14986). This result indicates that the spectral peak energy, Ep, is close 
to the low energy threshold of the instrument or lower than it. After 
fitting the spectrum with a Band function with alpha fixed at different 
values and by assuming the redshift of 0.145 (e.g., Leloudas et al. GCN 
14983; Mulchaey et al. GCN 14985), we find a 90% upper limit to the 
cosmological rest-frame peak energy, Ep,i, of ~15-20 keV and and 
isotropic-equivalent radiated energy, Eiso, of ~(6.5+/-0.10)x10^50 erg 
(flat FLRW Universe with H0=70 km/s/Mpc and Omega_M = 0.3).

Based on these estimates, GRB 130702A is consistent with the Ep,i - Eiso 
correlation holding for typical long GRBs and lies in the region bridging 
classical cosmological long GRBs with closer and weaker GRB-SN events like 
GRB060218/SN2006aj and XRF020903 (see 
http://www.iasfbo.inaf.it/~amati/grb130702a.pdf).
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