Residing in the heart of a dwarf galaxy four billion light years away is a mysterious cosmological object producing bursts of energy that only last a few milliseconds. New research about this Fast Radio Burst (FRB) has revealed a rarely seen astronomical environment around its source, where magnetic fields twist, turn, and undulate over time. This is the first detection of a magnetic field reversal observed from an FRB, and the first time this behavior has been observed in another galaxy.
An international team, led by a graduate research assistant at West Virginia University, Reshma Anna-Thomas, found the first evidence of magnetic field reversal in any FRB during the campaign. This discovery also strengthens the idea that at least a fraction of FRBs originate in a binary system, which is a system of two stars that orbit each other.
Shares Anna-Thomas, “We hoped to discover a high value of rotation measure, indicating
an extreme magnetized plasma environment but surprisingly, we also found that
it is highly variable and that the integrated magnetic field flips direction.”
Anna-Thomas and team used the National Science Foundation’s
Green Bank Telescope
(GBT) to observe FRB 20190520B for seventeen months—which is very brief, on astronomical
time scales. The peculiar characteristics of the FRB inspired a deeper dive into
the data, such as the high local dispersion measure, which is a sign of a dense
local environment, and a persistent radio source co-located with the FRB. Data
from Australia’s
Parkes Telescope
, also known as Murriyang, helped to complete this picture and strengthen our conclusion.
The Green Bank Telescope was able to observe the directional changes of waves from FRB20190520B as viewed through the lens of a massive star’s atmosphere. Image credit: NSF/GBO/P.Vosteen.
We hoped to discover a high value of rotation measure, indicating an extreme magnetized plasma environment but surprisingly, we also found that it is highly variable and that the integrated magnetic field flips direction. Reshma Anna THomas
Magnetic fields with such extreme turbulence and reversals have not been observed before in the cosmos, although there is a pulsar in our galaxy that comes close. That pulsar is in a binary system with a highly massive star. The researchers interpret their FRB’s observed magnetic properties as likely arising from the turbulent corona of a massive star, which provides a stunning lens through which we view the FRB binary. Explains Sarah Burke Spolaor, a professor and astronomer at WVU, “The furiously undulating and streaming plasma wind from the massive star’s atmosphere provides an ever-changing magnetic field along our line of sight to the FRB source. Polarization happens when light waves fluctuate in a specific orientation, and magnetic fields can realign that orientation. This is how we were able to observe the light’s changing orientations.”
Adds Ryan Lynch, a GBO scientist who supported this research, “The high sensitivity of GBT, its capabilities for observing high frequencies, and to record full polarization data, were crucial for the study. It’s one of the best telescopes available for studying FRBs.”
The Green Bank Observatory and the National Radio Astronomy Observatory are major
facilities of the National Science Foundation, operated under cooperative agreement
by Associated Universities, Inc.
West Virginia University’s Center for Gravitational Waves and Cosmology (GWAC)
addresses cutting-edge astrophysics problems that can be solved most effectively
through interdisciplinary collaboration across physics, astronomy, mathematics,
computer science and engineering. The Center explores the origins of the universe
and the fundamental processes involved in galaxy formation, stellar evolution,
and star formation. Through the agency of a collaborative network of experts,
our mission focuses on research, education and outreach.
Reshma Anna-Thomas and Sarah Burke Spolaor acknowledge support for their research
from NSF grant AAG-1714897.
Publication:
https://www.science.org/doi/10.1126/science.abo6526
Media Contacts:
Jill Malusky, Public Information Officer, Green Bank Observatory
jmalusky@nrao.edu , 304-460-5608
Holly Legleiter, Public Relations Coordinator,
WVU Center for Gravitational Waves and Cosmology
hlegleiter@mail.wvu.edu , 304-685-5301