GCN Circular 19456
Subject
GRB 160521B: Theoretical estimate of the redshift and urgent need for further x-ray observations
Date
2016-05-24T19:29:15Z (8 years ago)
From
Remo Rufinni at ICRA <ruffini@icra.it>
R. Ruffini, Y. Aimuratov, L. Becerra, C.L. Bianco, M. Kovacevic, R.
Moradi, M. Muccino, A.V. Penacchioni, G.B. Pisani, D. Primorac, J.
Rueda, Y. Wang report:
From preliminary data of GRB 160521B detected by the Fermi satellite (Yu
& Veres, GCN 19443) and from the presence of both gamma-ray (Fermi-GBM,
8 keV - 40 MeV) and GeV emission (Fermi-LAT, 0.1-100 GeV, see Axelsson
et al., GCN 19444) it is likely that this source is a Binary driven
Hypernova (BdHN) at very high redshift.
Following Ruffini et al. 2016 (arXiv:1602.02732), it lies in the BdHN
region of the Ep-Eiso plane for selected values of the redshift above
0.5 (see purple filled circles in Fig.[1]). The observed GeV emission
implies that the source cannot be a XRF.
The current paucity of data of the X-ray afterglow (Page et al., GCN
19448) is surprising and should be further examined up to late times
taking as an example GRB 090423 at z = 8.
Assuming that GRB 160521B is actually a BdHN, we can test the overlap of
its X-ray flux with the prototypical BdHN sources (see Pisani et al.
2013, A&A, 552, L5). In Fig.[2] it is plotted the single available data
point (Page et al., GCN 19448), not yet observed dimming, of GRB 160521B
X-ray luminosity, assuming 20 different values of the redshift from 0.5
(the lowest blue point) to 10 (the highest one) in steps of 0.5.
From these preliminary data, GRB 160521B is a BdHN with possible
redshift z > 2.5 all the way up to z ~ 10, assuming that the single
observed X-ray data point belongs to the afterglow. A deep search for
the afterglow in the X-ray band is indeed crucial to define the nature
of this source.
[1] http://www.icranet.org/documents/GRB160521b_Fig1.pdf
[2] http://www.icranet.org/documents/GRB160521b_Fig2.pdf