Almost exactly a year after an international group of astronomers reported the first ever merger of two neutron stars, a team of researchers from the University of Maryland claim to have identified a direct relative of that event.
In October 2017, astronomers from the Laser Interferometer Gravitational-wave Observatory (LIGO) recorded a simultaneous detection of light and gravitational waves from the same source, and named it GW170817.
This was two years after NASA's Neil Gehrels Swift Observatory reported and localised a gamma-ray burst in 2015, which was later named GRB150101B.
However, follow-up observations by NASA's Chandra X-ray Observatory, the Hubble Space Telescope (HST) and the Discovery Channel Telescope (DCT) this week suggest that the neutron star merger named in 2017 and the gamma ray burst first named in 2015 may be directly related.
"It's a big step to go from one detected object to two," Eleonora Troja, an associate research scientist in the UMD Department of Astronomy.
"Our discovery tells us that events like GW170817 and GRB150101B could represent a whole new class of erupting objects that turn on and off--and might actually be relatively common."
Troja and her colleagues suspect that both GRB150101B and GW170817 were produced by the same type of event: a merger of two neutron stars. These catastrophic coalescences each generated a narrow jet, or beam, of high-energy particles. The jets each produced a short, intense gamma-ray burst (GRB - a powerful flash that lasts only a few seconds.
GW170817 also created ripples in space-time called gravitational waves, suggesting that this might be a common feature of neutron star mergers.
The apparent match between GRB150101B and GW170817 is striking, the astronomers said, as both produced an unusually faint and short-lived gamma ray burst and both were a source of bright, blue optical light and long-lasting X-ray emission.
The host galaxies are also remarkably similar, based on HST and DCT observations. Both are bright elliptical galaxies with a population of stars a few billion years old that display no evidence of new star formation.
"We have a case of cosmic look-alikes," said study co-author Geoffrey Ryan. "They look the same, act the same and come from similar neighborhoods, so the simplest explanation is that they are from the same family of objects."
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