Fast Radio Bursts
By: Asme Iiest Shibpur Student Section
Tags: Space, Physics, Technology, Fast Radio Burst, Science

By Tannishtha Bag, Sunam Biswas and Kshitij Gupta

Comprehending events occurring far and beyond in the Universe has always been the primary focus of Astrophysicists. Studying radio light from stars, galaxies, black holes, and other astronomical objects is a great way to learn about the anatomy and life events of these celestial structures. Unexpectedly, similar research on periodic signals from pulsars (rotating neutron stars) landed us in front of a new Mystery.

A mysterious super powerful blast (called FRBs) carrying as much energy in radio waves as the Sun radiates in a month, arrived on July 24, 2001. It went unnoticed until 2006 when a West Virginia University undergraduate student named David Narkevic and his adviser, Duncan Lorimer, discovered the signal hidden in archival data taken in 2001 by the Parkes radio dish in Australia.

In radio astronomy, a fast radio burst (FRB) is a transient radio pulse of length ranging from a fraction of a millisecond to a few milliseconds, caused by some yet unknown high-energy astrophysical process. The estimated average release of energy by FRB is as much as the Sun does in 3 days. Fast radio bursts are named by the date on which the signal gets recorded, in the format — FRB YYMMDD.

Letting imaginations run wild made people reason this event with many theories ranging from everything between, Aliens trying to communicate to the last gasp of black holes. One possibility involves randomly moving high-energy electrons generating radio waves as they interact with magnetic fields. Supermassive black holes, supernova remnants, and hot gas sitting in galaxies often generate radio waves this way. Blitzars were a proposed explanation in 2013. In 2014, it was suggested that the resulting expulsion of the pulsar magnetospheres that followed dark matter induced collapse of pulsars could be the source of fast radio bursts. In 2015, it was suggested that FRBs are caused by explosive decays of axion nanoclusters. Another exotic possible source is cosmic strings that produced these bursts as they interacted with the plasma that permeated the early Universe. In 2016 the collapse of the magnetospheres of Kerr– Newman black holes was proposed to explain the origin of the FRBs’ “afterglow” and the weak gamma-ray transient. Different possibilities kept surfacing in the consequent times.

Multiple such radio pulses have been detected and recorded over the years. FRB 200428, FRB200914, and FRB200919 being the recent ones. FRB 200428 is the first Galactic radio burst (detected inside the Milky Way) that is as bright as the FRBs observed in other, nearby galaxies, thus making it to the headlines along with the hope of understanding the causes of FRBs better. It was detected coming from a highly magnetized stellar remnant (a magnetar) in our Galaxy. The radio waves were accompanied by X-ray emissions too. One possible mechanism for the formation of such an FRB can be the collision of particles of a successive sub-millisecond long flare of electrons and other charged particles produced by a magnetar.

It is believed that hundreds of similar bursts explode across the sky every day, but might have gone undetected until now since present radio telescopes focus on only small patches of the sky at an instant. Future radio observatories will be able to survey larger fractions of the sky at once and could count more such bursts. The possibility of using these bursts to pinpoint possible mergers between neutron stars, which general relativity predicts should emit gravitational waves (A signal that has so far eluded detection), brings more excitement to all the efforts being put to solve the riddle of FRBs.