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uGMRT enables study of environment around rare transient object 215 million light years away


For the first time, astronomers have obtained observational evidence of emissions originating from a Fast Blue Optical Transient (FBOT) object, particularly from within the radio frequency bandwidth.

Located 215 million light years away, the source, named AT 2018cow, was tracked for more than two years by scientists at the TIFR-National Centre for Radio Astrophysics (NCRA) using their own upgraded Giant Metrewave Radio Telescope (uGMRT).

FBOTs are rare and very difficult to spot, given that they luminate and fade out within a matter of time. Even rarer is getting any evidence of FBOTs under low radio bands of the electronic spectrum, with just four FBOTs discovered so far.

The researchers tried to understand the environment around the star system and some of the observations were possible due to the uGMRT, which is an array of 30 antennas operating in very low radio frequency, near Khodad in Junnar taluka of Pune.

“AT 2018cow is the first FBOT which has been observed for a period this long. According to the observations, the density of the medium dropped and suggest that this could be some kind of exotic source,” said lead researcher Poonam Chandra.

AJ Nayana, co-author of the study published in the Astrophysical Journal Letters on Friday, said such depleting density could mean that the source star was shedding mass at a much faster rate towards the end of its lifetime.

The emissions were found to travel at speeds 20 per cent the speed of light even 257 days after they left the source system following the explosion.

The speeds of these inhomogeneous emissions, mostly photons and no solid matter, were found to be 100 times faster towards the fag end of the star’s lifetime.

Radio emissions, scientists say, help understand the environment around FBOTs. “One can get to trace the footprints of the progenitor star system even before it exploded,” said Chandra.



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