Dying stars' cocoons could be new source of gravitational waves

 Although astrophysicists theoretically should be able to detect gravitational waves from a single, non-binary source, they have yet to uncover these elusive signals. Now researchers suggest looking at a new, unexpected and entirely unexplored place: The turbulent, energetic cocoons of debris that surround dying massive stars.

Now Northwestern University researchers suggest looking at a new, unexpected and entirely unexplored place: The turbulent, energetic cocoons of debris that surround dying massive stars.

For the first time ever, the researchers have used state-of-the-art simulations to show that these cocoons can emit gravitational waves. And, unlike gamma-ray burst jets, cocoons' gravitational waves should be within the frequency band that the Laser Interferometer Gravitational-Wave Observatory (LIGO) can detect.

"As of today, LIGO has only detected gravitational waves from binary systems, but one day it will detect the first non-binary source of gravitational waves," said Northwestern's Ore Gottlieb, who led the study. "Cocoons are one of the first places we should look to for this type of source."

Gottlieb will present this research during a virtual press briefing at the 242nd meeting of the American Astronomical Society. "Jetted and turbulent stellar deaths: New LIGO-detectable sources of gravitational waves" will take place on Monday, June 5, as a part of a session on "Discoveries in Distant Galaxies."

Gottlieb is a CIERA Fellow at Northwestern's Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). Northwestern co-authors of the study include professors Vicky Kalogera and Alexander Tchekovskoy, postdoctoral associates Sharan Banagiri and Jonatan Jacquemin-Ide and graduate student Nick Kaaz.

New source was 'impossible to ignore'

To conduct the study, Gottlieb and his collaborators used new state-of-the-art simulations to model the collapse of a massive star. When massive stars collapse into black holes, they may create powerful outflows (or jets) of particles traveling close to the speed of light. Gottlieb's simulations modeled this process -- from the time the star collapses into a black hole until the jet escapes.

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