AsianScientist (Oct. 25, 2017) – Scientists in Japan report in the Publications of the Astronomical Society of Japan that they have recorded optical and infrared signals from a kilonova produced by the merger of two neutron stars.
On 17 August 2017, the LIGO-Virgo collaboration alerted more than 90 astronomy teams around the world that they had detected a signal (GW170817) consistent with the merger of two neutron stars.
“Thanks to the combination of the data from the LIGO detectors in the US and the Virgo detector in Europe, this was the best ever localized gravitational wave source,” said Professor Raffaele Flaminio of the National Astronomical Observatory of Japan.
The Japanese collaboration of Gravitational wave Electro-Magnetic (J-GEM) follow-up is a research project to search for optical counterparts of gravitational wave sources because optical observations give us different information than gravitational wave observations. Indeed, multi-messenger astronomy—observing the same phenomenon with both gravitational waves and normal light—is needed to paint the full picture of the phenomenon.
Neutron star mergers are expected to have strong optical and infrared light emissions, so J-GEM sprang in to action. Using a network of telescopes around the world, including the Subaru Telescope in Hawaii and the 1.4-meter Infrared Survey Facility telescope in South Africa (run by Nagoya University and Kagoshima University), the researchers observed the source of the gravitational waves, located 130 million light-years away in the Hydra constellation.
As they watched the object change day by day, they realized that they were observing the first ever confirmed kilonova. The time evolution of the color and brightness of the object at the origin of the gravitational waves were too rapid to be a supernova, but matched the simulations of a kilonova made by the ATERUI supercomputer at the National Astronomical Observatory of Japan.
“We were so excited to see the how the brightness evolution rapidly day by day, made possible by facilities operated by Japanese institutes distributed all over the world,” said Assistant Professor Yousuke Utsumi of Hiroshima University, who is also a scientist in the J-GEM collaboration.
The article can be found at: Tanaka et al. (2017) Kilonova from Post-merger Ejecta as an Optical and Near-Infrared Counterpart of GW170817.
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Source: National Astronomical Observatory of Japan.
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