A new fast radio burst (or “FRB”) has been discovered that appears to be the second known example of a repeating and highly active FRB. Located in a metal-poor dwarf galaxy, FRB 190520B, discovered by an international team of astronomers, raises more questions about the origin of these short but powerful emissions.
As the name suggests, an FRB is a rapid emission of radio waves lasting no more than a few milliseconds, releasing an instantaneous energy equivalent to 500 million times that of our sun. Most FRBs come from other galaxies, and only one has been found in the Milky Way. They are so mysterious that we can’t even get a detailed look at their innermost features, such as the possibility to repeat themselves (or not).
Fewer than 5% of identified FRBs relapse – but FRB 190520B appears to be an exception to the rule. Initial emission detection by Dr. Chenhui Niu of the National Astronomical Observatory (NAOC) of the Chinese Academy of Sciences while processing data obtained through the Rapid Survey of Co-occurrence Radio Astronomy (CRAFTS) in 2019.
The emission was then found in data later that year, and subsequent follow-up observations showed it was repeating. New observations using the Subaru telescope installed in Hawaii show that these signals come from an ancient dwarf galaxy nearly 3 billion light-years away, and they look like “brothers” to signals from another repeating fast radio burst sisters” found.
New Fast Radio Burst Mystery
Data obtained by the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) telescope showed that the object continued to emit weaker radio waves between its outbursts. “These characteristics make it very similar to the first FRB in 2016, also located by the VLA,” noted Casey Law of Caltech.
He referred to FRB 121102A: Determining its source provided the first information on the environment and discharge distances. The combination of sudden and repeated flashes, plus sustained radio emissions between bursts, all came from a compact region, putting the object in a different location from other FRBs.
“We now have two of these, and that raises some important questions,” Law noted. The differences between the 190520B and 121102A FRBs and all other FRBs support the possibility that both are two different types of FRBs. Astronomers have proposed two possibilities: Either there are two different mechanisms that generate FRBs, or the objects that cause FRBs behave differently during their evolution.
Currently, some of the leading candidates for FRBs are extremely dense neutron stars left behind by massive stars after supernovae. They could also come from magnetars, neutron stars with extremely strong magnetic fields.
In this case, FRB190520B appears to be in a complex plasma environment with characteristics similar to a superluminous supernova; therefore, it may be a “nascent” FRB. “We further hypothesized that FRB 121102A and FRB 190520B represent early stages of an evolving FRB population. A coherent picture of the origin and evolution of FRBs should emerge in just a few years,” concludes Dr. Li, from NAOC.
Articles with findings published in journals nature.
Source: Nature; Pathway: NRAO