TITLE:   GCN CIRCULAR
NUMBER:  29481
SUBJECT: GRB 210210A as a BdHN II
DATE:    21/02/11 16:53:10 GMT
FROM:    Remo Rufinni at ICRA  <ruffini@icra.it>

R. Ruffini, R. Moradi, Y. Aimuratov, C. L. Bianco, M. Karlica,  J.A. Rueda,
N. Sahakyan, Y. Wang, Liang Li, S. S. Xue on behalf of the ICRANet team,
report:


GRB 210210A has T90=6.6s , observed by Swif-BAT (GCN 29467), with z=0.715
(GCN 29450), with an isotropic energy of E_iso ~ 2 x 10^51 erg, is the twin
of GRB 180728A ( Wang et al 2019 ApJ 874 39) with an  isotropic energy of
E_iso ~ 3 x 10^51 erg. It presents the typical characteristic of a subclass
of long GRBs called  Binary-driven Hypernovae of type II (BdHN II)
originating from a tight binary of a FeCO Core undergoing a supernova
explosion in presence of a companion neutron star (NS) which undergoes
hypercritical accretion.  The outcome (see Fig. [1]) is a new binary
composed by a more massive NS (MNS) and a newly born NS (*v*NS).


In both GRB 210210A and 180728A The GeV emission is not observed (GCN
29473); as it is expected in BdHN II. The follow-up observation in the
X-ray afterglow emission is recommended in order to determine the spin and
magnetic field of the new Neutron star (vNS) in this BdHN. We look forward
to possible data obtained from Fermi-GBM to recognize the supernovae rise
(SN-rise)(see Fig. [2]).

Using the averaged observed value (Cano et al., 2016), and considering the
redshift z=0.715 (A. Rossi et al., GCN 23055), a bright optical signal will
peak at 22 +/- 5 days after the trigger. However, the high redshift z=0.715
makes the observation challenging for this source.


Fig. 1: http://www.icranet.org/documents/SPHsimulation_CO-starSN-NS.pdf
Fig. 2:
http://www.icranet.org/documents/X-ray_afterglow_GRB180728A-GRB210210A.pdf


[GCN OPS NOTE: Per author's request, the last paragraph changes from:
"Using the averaged observed value (Cano et al., 2016), and considering the
redshift z=0.715 (A. Rossi et al., GCN 23055), a bright optical signal will
peak at 22 +/- 5 days after the trigger. However, the high redshift z=0.715
makes the observation challenging for this source."
to:
"Considering the red shift Z=0.715 (Ugarte et al, GCN 29450) a Supernova optical signal
will peak at 22 +/- 5 days after the trigger. However, the high redshift z=0.715,
makes the observation challenging for this source."
Removeing the Cano portion of the first sentence and correcting the Rossi citation
with the Ugarte citation.]