Two Predictions of supernova: GRB 130427A / SN 2013cq and GRB 180728A / SN 2018fip

Understand

On 2018 July 28, GRB 180728A triggered \textit{Swift} satellites and, soon after the determination of the redshift, we identified this source as a type II binary-driven hypernova (BdHN II) in our model.

• Consequently, we predicted the appearance time of its associated supernova (SN), which was later confirmed as SN 2018fip.
• A BdHN II originates in a binary composed of a carbon-oxygen core (CO$_{\rm core}$) undergoing SN, and the SN ejecta hypercritically accrete onto a companion neutron star (NS).
• From the time of the SN shock breakout to the time when the hypercritical accretion starts, we infer the binary separation $\simeq 3 \times 10^{10}$ cm.