Figure 2: Artist's impression of the GW170817 kilonova
Credit: NAOJ
Astronomers have tracked down the source of a gravitational wave and discovered the first observed kilonova: a nuclear furnace 100 million times brighter than the Sun producing thousands of times the entire mass of the Earth in heavy elements such as precious metals.
On August 17, 2017 the LIGO-Virgo collaboration alerted more than 90
astronomy teams around the world, that they had detected a signal
(GW170817) consistent with the inspiral and merger of two neutron stars.
Dr. Raffaele Flaminio (NAOJ and CNRS/LAPP), a scientist from the Virgo
and KAGRA collaborations, explains that "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."
J-GEM (Japanese collaboration of Gravitational wave Electro-Magnetic
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 Hawai'i
and the 1.4-m IRSF telescope in South Africa (run by Nagoya University
and Kagoshima University), they observed the source located 130 million
light-years away in the constellation Hydra, trying to discern its true
nature. As they watched the object change day by day, they realized that
they were observing the first ever confirmed kilonova.
Astronomers have long searched for sites in the Universe where the
heavy elements were produced by rapid neutron capture (r-process)
reactions. One possible candidate was kilonova explosions which are
predicted to produce 10,000 times the mass of the Earth in rare earth
elements and precious metals.
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 rapid brightness evolution revealed
day by day through observations at facilities operated by Japanese
institutes distributed all over the world." said Dr. Yousuke Utsumi
(Hiroshima University), a scientist in the J-GEM collaboration.
Movie: The optical and near-infrared counterpart of GW170817 capture by HSC mounted on the Subaru Telescope. (Credit: NAOJ)
Two papers on this research will be published in Publications of the
Astronomical Society of Japan (PASJ) on October 16, 2017 (Utsumi et al.,
"J-GEM observations of an electromagnetic counterpart to the neutron
star merger GW170817", and Tanaka et al., "Kilonova from post-merger
ejecta as an optical and near-infrared counterpart of GW170817").
Another paper is also submitted to PASJ (Tominaga et al., "Subaru Hyper
Suprime-Cam survey for an optical counterpart of GW170817").
Links
Links
- Subaru / Hyper Suprime-Cam image for the optical follow-up to GW170817 (J-GEM Project)
- Press release from CfCA, NAOJ
- Press release from Gravitational Wave Project Office, NAOJ
- Press release from School of Science, University of Tokyo
- Press release from Nagoya University
- Press release from Hiroshima University
Source: Subaru Telescope
