A new collaborative study involving Australian researchers from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) promises new insights on the origin of a class of radio pulses called Fast Radio Bursts (FRBs). These bursts, so bright that astronomers can see them from billions of light years away, have been studied for over a decade. However, the origin of FRBs remains one of the greatest mysteries in astronomy today.
Australia has played a key role in the discovery and study of FRBs. Now, in this landmark study, researchers are approaching the problem in a new way, looking for the presence of ripples in the curvature of space and time (called gravitational waves) that could be associated with the radio emissions.
This recent international study has focused on the FRB models that could also produce emissions in gravitational waves. Associating a gravitational wave signal with an FRB could provide startling new evidence on the forces driving FRBs.
Scientists who conducted the study were provided with data from 800 fast radio bursts from a Canadian telescope called CHIME. OzGrav Associate Investigator Eric Howell (from the University of Western Australia) initiated the search with scientists from the LIGO (USA) and Virgo (Italy) collaborations.
There are many scientific models that predict FRBs - over 50 have been published. Some models suggest a cataclysmic origin for FRBs; this means that the bursts could result from explosive astronomical events such as supernovae that signal the death of a massive star, or from violent collisions of dead stars such as black-holes or neutron stars.
Other models suggest that FRBs could be the occasional outbursts from a more stable source, such as a neutron star – these are termed stable or persistent as they could repeat over time. A small proportion of FRBs have been observed to repeat but scientists still don’t know if this applies to all of them. Currently, FRBs are labeled as ‘repeaters’ or ‘non-repeaters’.
FRB models that could also produce gravitational waves include well-predicted signals such as colliding pairs of neutron stars and black-hole neutron stars.
“We know we can detect these types of gravitational wave signals to fairly well known distances” says Howell. “If we have an idea of the maximum FRB distance and it’s within our gravitational wave range, we should be able to make a detection or rule out a particular source.”
The search also looked for generic bursts of gravitational waves that could occur from less understood sources; these could be chaotic pulses or ‘bursts’ of gravitational wave energy. These emissions could be the outbursts of neutron stars or from some other exotic phenomena.
OzGrav PhD student Teresa Slaven-Blair (UWA), who played a role in the analysis for the resulting paper, says that ”by searching for gravitational waves around the time and sky position of each FRB, we can improve the sensitivity of the search and go deeper”.
“This study is a vital stepping stone in understanding fast radio bursts (FRBs) - we are not able to rule out any gravitational wave association yet, but future observation runs at higher sensitivity may be able to capture more FRBs,” says Howell.
This study is another example of how gravitational wave astronomy is playing an increasingly important role in our understanding of the cosmos. Making use of distortions in space and time to probe exotic phenomena, such as fast radio bursts, is real next generation astronomy.
The article is published in the Astrophysical Journal here and can be cited as: LVK Collaborations et al. 2023, ApJ, 955, 155.
This result also featured in The Conversation.