2021/03/16 by R. Moradi, Liang Li, Moradi, R. +9
Physics and Astronomy · #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Astrophysical Phenomena (astro-ph.HE) #astro-ph.HE #gr-qc
paper · pdf · doi:10.48550/arxiv.2103.09158
Submitted for publication on February 26, 2021
arxiv created 2021/03/16 · arxiv updated 2021/03/17
GRB 180720B, observed by \it Fermi-GBM, with redshift z=0.653, isotropic energy E\rm iso=5.92× 1053 erg, and X-ray afterglow observed by the XRT onboard the Neil Gehrels Swift satellite, is here classified as a Binary-driven Hypernova I (BdHN I). BdHN I are long GRBs with a binary progenitor composed of a carbon-oxygen core (CO\rm core) and a neutron star (NS) companion with orbital period ∼ 5 min. The gravitational collapse of the CO\rm core generates a supernova (SN) and a new NS (νNS) at its center. The SN hypercritical accretion onto the companion NS triggers its gravitational collapse forming a black hole (BH). An electrodynamical process near the BH horizon leads to the long-lasting GeV emission with power-law luminosity L\rm GeV∝ t-1.19±0.04, powered by the BH rotational energy. Correspondingly, we determine the BH mass and spin. The νNS via its pulsar-like emission and fallback accretion injects energy into the magnetized SN ejecta generating synchrotron radiation. This explains the long-lasting X-ray afterglow with power-law luminosity LX ∝ t-1.48± 0.32, energized by the νNS rotational energy. We apply this to GRB 180720B determining the νNS magnetic field and spin. We also analyze the GRB 180720B emission observed by the High-Energy Stereoscopic System (H.E.S.S.), at 100-440 GeV energies, 10.1-12.1 h after the Fermi-GBM trigger. We propose that this short-term radiation of energy 2.4× 1050 erg and duration ∼ 103 s, is powered by a "glitch" event that suddenly injects relativistic electrons into the νNS magnetosphere during its slowing down phase.