[vsnet-grb-info 13239] GRB 130505A: Largest E_iso ever measured

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14576
SUBJECT: GRB 130505A: Largest E_iso ever measured
DATE:    13/05/05 20:03:36 GMT
FROM:    Alexander Kann at TLS Tautenburg  <kann at tls-tautenburg.de>

D. A. Kann (TLS Tautenburg), and S. Schulze (PUC, MCSS) report:

Using the energetics provided by the Konus-Wind detection (Golenetskii et
al. 2013, GCN 14575) of the extremely intense Swift GRB 130505A (Cannizzo
et al. 2013, GCN 14564), and employing k-correction (Bloom et al. 2003,
ApJ, 594, 674), we determine the isotropic energy release in the
bolometric band (rest-frame 1 keV - 10 MeV) to be (5.65 +/- 0.13) x 10^54
erg (log E_iso = 54.75 +/- 0.01).

The most isotropically energetic GRBs known so far (all in the rest-frame
bolometric band) are GRBs 990123, 080916C and 090323, for which log E_iso
~ 54.5 - 54.6 has been found (e.g., Kann et al. 2010, ApJ, 720, 1513).

This makes GRB 130505A the most energetic GRB known, and may indicate
either an ultra-luminous event or a high degree of collimation.

We additionally note that the nearby GRB 130427A (Maselli et al. 2013, GCN
14448; Golenetskii et al. 2013, GCN 14487) is also highly energetic, with
log E_iso,bol = 54.21 +/- 0.05, but this is about 3.5 times less than GRB
130505A.

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