GRBs, known for their intense luminosities which can rival the collective output of all stars in the observable universe within seconds, have been a focal point for astronomers. However, the technical limitations of the XRT instrument on the Neil Gehrels Swift Observatory satellite have historically restricted timely observations of these bursts' early X-ray emissions, typically within about 40 seconds of detection.
The research team tackled this challenge by analyzing data from the Swift GRB catalog, which includes 368 GRBs with measured distances spanning from 2005 to the end of 2023. Through their analysis, the team was able to identify early X-ray emissions in over 220 GRB events by exploiting the time dilation effects present at high cosmological redshifts. These findings provide crucial insights into the dynamics of the cosmos at its nascent stages.
"Our results not only extend our capabilities in observing the universe but also challenge our theoretical understanding of these monumental cosmic events," said Prof. Remo Ruffini, Director of ICRANet. "By observing GRBs at such high redshifts, we effectively see these events in slow motion, which dramatically increases our window of observation relative to their cosmological timeline."
In detailing their methodology, the team highlighted the cases of GRB 090423, GRB 090429B, and GRB 220101A, observed at redshifts of 8.233, approximately 9.4, and 4.61, respectively. These particular observations verified the collapse of the carbon-oxygen core and the formation of new neutron stars, which are thought to trigger the GRB under the binary-driven hypernova model. Additionally, the team observed the spin-up and subsequent slowdown of the neutron stars, potentially punctuated by brief gravitational wave emissions marking a transition in the star's rotation.
Moreover, the analysis of the redshift distribution within these GRB samples supports the hypothesis that certain types of hypernovae may evolve into binary neutron star systems, which later serve as progenitors for short GRBs. This correlation provides a novel perspective on the lifecycle of neutron stars and their role in the cosmos.
The findings, detailed in the team's publication in The Astrophysical Journal, promise to not only refine existing models of GRBs but also assist in planning future missions. Upcoming missions like THESEUS and HERMES, equipped with wide field-of-view X-ray instruments, are poised to take advantage of this methodology, providing immediate observations of GRB emissions without the delays that currently hamper our understanding.
Research Report:Probing electromagnetic-gravitational wave emission coincidence in a type I binary-driven hypernova family of long GRBs at very-high redshift
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