GCN Circular 32793

The prompt emission of the extraordinarily bright GRB 221009A was detected in space by Swift (Dichiara et al. GCNC 32632, Krimm et al. 32688), Fermi (Veres et al. GCNC 32636, Bissaldi et al. GCNC 32637, Lesage et al. GCNC 32642, Pillera et al. GCNC 32658, Omodei et al. GCNC 32760), AGILE (Ursi et al. GCNC 32650, Piano et al. GCNC 32657), INTEGRAL (Gotz et al. GCNC 32660), Solar Orbiter (Xiao et al. GCNC 32661), SRG (Lapshov et al. GCNC 32663), Konus (Frederiks et al. GCNC 32668), GRBAlpha (Ripa 
et al. GCNC 32685), STPSat-6 (Mitchell et al. GCNC 32746), HEBS (Liu et al. GCNC 32751). Various estimates of its prompt isotropic energy ranks it among the most energetic GRBs (Cenko et al. 2011, Atteia et al. 2017):
Gotz et al. GCNC 32660 -���������� Eiso = 8e53 ergs in [75 keV 1 MeV] ;
Frederiks et al. GCNC 32668 - Eiso = 3e54 ergs in [20 keV - 10 MeV ?] ;
Kann et al. GCNC 32762 -���������� Eiso = 6e54 ergs in [0.1 keV - 100 MeV] ;

We discuss here the chance to observe such an energetic GRB at redshift z = 0.151 (de Ugarte Postigo GCNC 32648, Castro-Tirado et al. GCNC 32686), considering the rate of such extremely energetic GRBs observed at higher redshifts.

Considering a flat cosmology with H0 = 67.4 km/s/Mpc and Omegam = 0.315 (Planck Collaboration et al. 2020), we extrapolate the rate of ���4 extremely energetic GRBs per year derived by Atteia et al. (2017) in the redshift range [1,5], to the volume of the nearby universe enclosed within z = 0.151.

- Assuming a constant GRB formation rate, we obtain 1 extremely energetic GRB per ~130 yr.
- Assuming the GRB formation rate of Palmerio & Daigne (2021), we obtain 1 extremely energetic GRB per ~520 yr.

We conclude that there is a ~10% probability to observe an event like GRB 221009A about 50 years after the discovery of the first GRB.

Bibliography :
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- Atteia, J.-L., Heussaff, V., Dezalay, J.-P., et al. 2017, ApJ, 837, 119
- Palmerio, J.T. & Daigne, F. 2021, A&A, 649, 166
- Planck Collaboration, Aghanim, N., Akrami, Y., et al. 2020, A&A, 641, A6