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Measuring gravitational waves to see inside stars

The observation of supernovae gives us very interesting insight of how our universe works. In particular, the type II supernovae are looked closely. They are what happens when a massive star experiences a rapid collapse. This triggers a massive explosion that blows off the outer layers of the star, leaving behind a remnant neutron star. It is believed that this collapse released gravitational energy. To capture such event, astronomers are looking with great attention the Large Magellanic Cloud.

The idea of a team of astronomers from UK and Arizona is to measure the gravitational waves coming from stellar events in order to have a better understanding of the mechanism involved during for example a supernovae explosion. Due to the difficulty of measuring these gravitational waves, this task won’t be easy.

" The gravitational waves are emitted from deep inside the core-collapse supernovae, which may allow astrophysical parameters, such as the equation of state, to be measured from the reconstruction of the gravitational-wave signal.”

Dr. Powell, University of Glasgow, UK

This ground-based image of the Large Magellanic Cloud was taken by the German astrophotographer Eckhard Slawik. It spans 10 x 10 degrees. Just to the left of the middle of this image the largest star-forming region in the Local Group of galaxies, 30 Doradus, is seen as a red patch. N11B itself is seen in the upper right part of the LMC.

Dr Powell and her team are looking for a core-collapse supernova signal using an Advanced LIGO and Virgo gravitational-wave  detector  network. They are hoping these instruments will allow them to measure astrophysical parameters of the source.

"The gravitational waves are emitted from deep inside the core of the star where no electromagnetic radiation can escape. This allows a gravitational wave detection to tell us information about the explosion mechanism that can not be determined with other methods. We may also be able to determine other parameters such as how rapidly the star is rotating."

Beside the difficulty inherent of such a measurement, one problem they are facing is coming from transient noise artefacts that may mimic a true gravitational-wave  signal.   In  their last  paper [1],  they  outline  a  procedure  implemented  in  the  Supernova Model Evidence Extractor that determines if a core-collapse supernova signal candidate is a noise artefact, a rapidly-rotating core-collapse supernova signal, or a neutrino explosion mechanism core-collapse supernova signal.  While there are no guarantees at this point that they will find any signals that would demonstrate that supernovae are detectable, the team has high hopes. And given the possibilities that this research holds for astrophysics and astronomy, they are hardly alone!

Continue reading at: https://phys.org/news/2017-09-gravitational-stars-supernovae.html

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