The origin of one of the
most mysterious phenomena in the universe is becoming clearer. The phenomenon
is a repeating fast radio burst (FRB), an intense emission of radio waves that
lasts milliseconds, a one of a kind event. Only 24 FRBs have been observed and
only this one, FRB 121102, has been repeating.
The fact that it keeps
repeating has allowed astronomers to study this event like no other FRB. They
were able to confidently place its origin within the star-forming region of a
dwarf galaxy 3 billion light-years from Earth.
Researchers were also able
to start working out that a neutron star was likely causing it, and now thanks
to new observations, an international team has narrowed it down to just a few
hypotheses.
As reported in Nature, FRB
121102 is caused by a neutron star surrounded by a strong magnetic field. The
researchers suggest that this field could be either created by a massive black
hole ingesting materials or by magnetized wind within a nebula or supernova
remnant. This hypothesis comes from observations suggesting the radio emission
was polarized due to the magnetic field.
Magnetic fields can twist
light emissions and the stronger the field, the larger the twist.
“The only known sources in
the Milky Way that are twisted as much as FRB 121102 are in the Galactic
center, which is a dynamic region near a massive black hole. Maybe FRB 121102
is in a similar environment in its host galaxy,” lead author Daniele Michilli,
from ASTRON, said in an emailed statement. “However, the twisting of the radio
bursts could also be explained if the source is located in a powerful nebula or
supernova remnant.”
Daniele Michilli, PhD candidate at the
University of Amsterdam and ASTRON, the Netherlands Institute for Radio
Astronomy. This novel understanding of the source comes from combining
observations at the Arecibo Observatory and observations at even higher
frequencies from the Breakthrough Listen project at the Green Bank Telescope.
"The polarization
properties and shapes of these bursts are similar to radio emission from young,
energetic neutron stars in our galaxy," added co-author Andrew Seymour,
from the Arecibo Observatory. "This provides support to the models that
the radio bursts are produced by a neutron star.”
The team will continue to
monitor FRB 121102 in the hope of determining which scenario is more likely,
the black hole or the highly magnetized nebula.
"If we study the
properties of that source in more detail (e.g. try to observe with higher
resolution, look to see if it is changing in brightness with time, whether that
other source is also polarized, etc.) then we can hope to conclude whether it
represents an accreting black hole or a nebula," senior author Jason
Hessels, also from ASTRON, told IFLScience.
FRB 121102 is a unique radio
burst, but this research might allow us to understand all FRBs better.
Via IFLScience