Research: Short gamma-ray bursts traced farther into distant universe
Washington, November 22: Astronomers have developed the most extensive inventory to date of the galaxies where short gamma-ray bursts (SGRBs) originate.
Using several highly sensitive instruments and sophisticated galaxy modeling, the researchers pinpointed the galactic homes of 84 SGRBs and probed the characteristics of 69 of the identified host galaxies.
The astronomers also found that more SGRBs occurred at earlier times, when the universe was much younger -- and with greater distances from their host galaxies' centers -- than previously known. Surprisingly, several SGRBs were spotted far outside their host galaxies -- as if they were "kicked out," a finding that raises questions as to how they were able to travel so far away.
"This is the largest catalog of SGRB host galaxies to ever exist, so weexpect it to be the gold standard for many years to come," said Anya Nugent, a Northwestern graduate student who led the study focused on modeling host galaxies. "Building this catalog and finally having enough host galaxies to see patterns and draw significant conclusions is exactly what the field needed to push our understanding of these fantastic events and what happens to stars after they die."
When two neutron stars collide, they generate momentary flashes of intense gamma-ray light, known as SGRBs. While the gamma rays last mere seconds, the optical light can continue for hours before fading below detection levels (an event called an afterglow). SGRBs are some of the most luminous explosions in the universe with, at most, a dozen detected and pinpointed each year. They currently represent the only way to study and understand a large population of merging neutron star systems.
Since NASA's Neil Gehrels Swift Observatory first discovered an SGRB afterglow in 2005, astronomers have spent the last 17 years trying to understand which galaxies produce these powerful bursts. Stars within a galaxy can give insight into the environmental conditions needed to produce SGRBs and can connect the mysterious bursts to their neutron-star merger origins. So far, only one SGRB (GRB 170817A) has a confirmed neutron-star merger origin -- as it was detected just seconds after gravitational wave detectors observed the binary neutron-star merger (GW170817).
"In a decade, the next generation of gravitational wave observatories will be able to detect neutron star mergers out to the same distances as we do SGRBs today," Fong said. "Thus, our catalog will serve as a benchmark for comparison to future detections of neutron star mergers."
"The catalog can really make impacts beyond just a single class of transients like SGRBs," said Yuxin "Vic" Dong, study co-author and astrophysics Ph.D. student at Northwestern. "With the wealth of data and results presented in the catalog, I believe a variety of research projects will make use of it, maybe even in ways we have yet not thought of."
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