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GCN Circular 23019

GRB 180720B: Testing the universality of the newly born neutron star in BdHNe
2018-07-22T22:30:27Z (5 years ago)
Remo Rufinni at ICRA <>
R. Ruffini, Y. Aimuratov, C. L. Bianco, Y. C. Chen, D. M. Fuksman, M. Karlica, R. Moradi, D. Primorac, J.A. Rueda, N. Sahakyan, Y. Wang, on behalf of the ICRANet team, report:

GRB 180720B (Siegel et al., GCN 22973) is a long GRB with isotropic energy ~6.0e53 erg (Frederiks et al., GCN 23011). It belongs to the long GRB subclass of Binary Driven Hypernovae (BdHNe) (Ruffini et al., 2016, ApJ, 832, 136), with energies larger than 1e52 erg and GeV radiation, which allows the determination of the black hole mass (Ruffini et al., arXiv:1803.05476). It includes GRB 130427A associated to SN 2013cq (Ruffini et al., GCN 14526, Xu et al., GCN 14646), as well as GRB 160625B (Troja et al., 2017). The comparison of X-ray light-curves is attached [1], plotted in the rest frame of the sources. These sources are polar views from the normal to the plane of the binary progenitor (Ruffini et al., arXiv:1803.05476). In GRB 180720B, which has redshift z = 0.654 (GCN 22996), being a BdHN, a supernova is expected to peak, using the averaged observed value (Cano et al., 2016), at 21.8 +/ 4.3 day after the trigger (11 August 2018, uncertainty from August 7th to August 15th): the prolonged observations of the afterglow in all bands, especially the optical band, is recommended to further probe the nature of the supernova and of the newly born neutron star, strikingly constant in all BdHNe (see also Becerra et al., arXiv:1803.04356).

[1] Link:

Caption of figure: Three BdHNe with polar views from the normal to the plane of the binary progenitor, pointing to the similarities. GRB 130427A with redshift z=0.34 is associated to the companion supernova SN 2013cq. GRB 160625B has redshift z=1.406, which is too far for the optical observation of the associated supernova (Woosley & Bloom, 2006). GRB 180720B with redshift z=0.654 is expected to have the observation of an associated supernova.
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