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Exploring the Link Between Magnetars, Fast Radio Bursts, and Gravitational Waves
Fast radio bursts (FRBs) are enigmatic astrophysical phenomena that manifest as brief bursts of radio wave energy, occurring anywhere from a fraction of a millisecond to several seconds. Most FRBs originate from beyond our galaxy, although a notable exception has been detected from within the Milky Way. Among these occurrences, some FRBs have been observed to repeat, adding layers of intrigue to their origin and nature.
Astrophysicists generally attribute the generation of FRBs to high-energy astrophysical processes, but the precise mechanisms remain largely unknown. Recent efforts have focused on using gravitational waves (GWs) to study FRBs and their characteristics more systematically. Notably, the only confirmed source of an FRB in our galaxy is a magnetar known as SGR 1935+2154, which emitted an FRB in 2020—the first instance in which an FRB has been definitively linked to a known source. Despite being roughly 20,000 light-years distant, SGR 1935+2154 has become a focal point for researchers attempting to unravel the mysteries surrounding FRBs.
A recent study published in The Astrophysical Journal utilized the British-German GEO600 gravitational wave detector to investigate any correlations between rapidly occurring FRBs and gravitational waves. Authored by A. G. Abac from the Max Planck Institute for Gravitational Physics, the research is titled “A Search Using GEO600 for Gravitational Waves Coincident with Fast Radio Bursts from SGR 1935+2154.”
The energetic nature of both FRBs and magnetars makes their association particularly significant for cosmological research, although many questions still remain. Some magnetars are known to emit either repeating FRBs or X-rays, and these bursts can be accompanied by significant star quakes caused by the release of internal stress in the neutron star’s crust. These quakes could theoretically induce gravitational waves as well, prompting researchers to explore this possibility further.
James Lough, leading the GEO600 gravitational-wave detection team, stated, “Observing fast radio bursts and gravitational waves from a magnetar almost simultaneously could provide the evidence we have long sought.” Such simultaneous observations would help confirm whether FRBs and gravitational waves stem from similar stellar quakes generated by the neutron star. Collaboration among international scientists was key to analyzing GEO600’s continuous data during the FRB occurrences from SGR 1935+2154.
During the period from April 2020 to October 2022, SGR 1935+2154 experienced three episodes of FRBs, all while GEO600 was operational. Lough emphasized the significance of GEO600 being active as other detectors underwent upgrades, which might have otherwise led to missed opportunities for gravitational wave detection.
Upon examining the data, researchers found no gravitational wave events coinciding with the detected FRBs, but the results still yielded valuable insights. The proximity of the magnetar allowed for new understanding, even in the absence of a detection.
This investigation isn’t isolated; previous attempts have also involved GW detectors in searches for gravitational waves associated with FRBs, along with bursts from magnetars and glitches from pulsars. Other collaborations, such as LIGO, Virgo, and KAGRA, have yet to successfully detect combined occurrences, though they have established upper limits on the energy of any potential gravitational waves emitted during such events.
The larger and more advanced LVK detectors have provided data indicating that the gravitational-wave energy produced during the recent FRBs from SGR 1935+2154 must be significantly lower than initially theorized—up to 10,000 times less than previous estimates suggested.
Various models attempt to explain the association of gravitational waves with FRBs, yet current observations lack sufficient sensitivity to differentiate among them. Nevertheless, by establishing energy limits, ongoing gravitational wave studies are helping to refine theoretical models.
This connection between gravitational waves and FRBs remains a nascent field of study. While previous observations from LIGO/Virgo didn’t capture data during the latest FRBs, forthcoming operational upgrades may enhance detection capabilities. Historically, astrophysicists have suspected magnetars could be the source of FRBs, and the confirmed emissions from SGR 1935+2154 lend credence to this hypothesis. However, the underlying processes that give rise to FRBs still elude a clear understanding.
If future observations from upgraded LIGO/Virgo and KAGRA facilities succeed in recording gravitational waves coinciding with FRBs, it could represent a significant advancement in cosmic research. The study’s authors noted, “With enhanced sensitivity, any upcoming FRB from SGR 1935+2154 during the ongoing observing run presents a promising chance to delve further into the gravitational wave-fast radio burst connection.”
As the scientific community remains hopeful, Karsten Danzmann, director at the Max Planck Institute for Gravitational Physics, expressed optimism for renewed activity from SGR 1935+2154 in the coming months, after a period of dormancy. The current observing run, which will continue through June 2025, aims to further investigate the potential links between FRBs and gravitational waves, potentially unlocking answers to one of astronomy’s oldest questions.
More information: A. G. Abac et al, A Search Using GEO600 for Gravitational Waves Coincident with Fast Radio Bursts from SGR 1935+2154, The Astrophysical Journal (2024). DOI: 10.3847/1538-4357/ad8de0
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phys.org