Astrophysicists have primarily detected gravitational waves from binary systems, such as mergers of black holes or neutron stars. However, researchers at Northwestern University propose exploring a new and unexplored avenue: the turbulent cocoons of debris surrounding dying massive stars. Using advanced simulations, they have demonstrated that these cocoons can emit gravitational waves. Unlike gamma-ray burst jets, the gravitational waves from cocoons should fall within the frequency range detectable by the Laser Interferometer Gravitational-Wave Observatory (LIGO).
The study’s lead researcher, Ore Gottlieb from Northwestern, believes that although LIGO has so far only detected gravitational waves from binary systems, it will eventually identify the first non-binary source. According to Gottlieb, cocoons should be one of the prime locations to search for this type of source.
This research will be presented by Gottlieb during a virtual press briefing at the 242nd meeting of the American Astronomical Society, as part of a session on “Discoveries in Distant Galaxies.” The study involved collaboration with other Northwestern researchers, including 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’
Scientists from Northwestern University have discovered a potential new source of gravitational waves: the turbulent cocoons of debris surrounding dying massive stars. While gravitational waves have only been detected from binary systems like black hole or neutron star mergers, researchers believe that single, non-binary sources should also emit these waves. Using advanced simulations, the team showed that the cocoons around dying stars can generate gravitational waves that fall within the frequency range detectable by the Laser Interferometer Gravitational-Wave Observatory (LIGO).
Ore Gottlieb, the lead researcher, stated that although LIGO has only detected gravitational waves from binary systems thus far, it will eventually detect the first non-binary source. According to Gottlieb, cocoons should be one of the primary targets for detecting this type of source.
The research, titled “Jetted and turbulent stellar deaths: New LIGO-detectable sources of gravitational waves,” was presented by Gottlieb during a virtual press briefing at the 242nd meeting of the American Astronomical Society. The study involved collaboration with other Northwestern researchers, including Vicky Kalogera, Alexander Tchekovskoy, Sharan Banagiri, Jonatan Jacquemin-Ide, and Nick Kaaz.
Call to action to look at cocoons
Gottlieb noted that if cocoons indeed generate gravitational waves, LIGO should be capable of detecting them in its upcoming runs. Traditionally, researchers have focused their search for single-source gravitational waves on gamma-ray bursts or supernovae, but there are doubts about LIGO’s ability to detect those signals.
Gottlieb explained that both jets and supernovae are highly energetic explosions, but gravitational waves can only be detected from asymmetrical explosions with higher frequencies. Supernovae, being spherical and symmetrical, do not disrupt the balanced mass distribution within the star to emit detectable gravitational waves. Gamma-ray bursts, on the other hand, have durations of dozens of seconds, resulting in frequencies that fall below the sensitivity range of LIGO.
Instead, Gottlieb proposes that astrophysicists shift their focus to cocoons, which are both asymmetrical and highly energetic. He considers the study a call to action for the scientific community to explore cocoons as a potential source of gravitational waves. Additionally, since cocoons are also known to emit electromagnetic radiation, they could potentially be observed as multi-messenger events. By studying cocoons, scientists can gain further insights into the inner workings of stars, the properties of jets, and their occurrence in stellar explosions.
The study is titled “Jetted and turbulent stellar deaths: New LIGO-detectable gravitational wave sources.”
Source: Northwestern University