Long lasting ‘radio rebound’ caused by jets from the recent gamma-ray burst

Within a fraction of seconds, a massive star which was about 2 billion light-years away and even more than that lost a long fight of million years against the gravity and got collapsed. This has lead to the triggering of supernova and at its center, it has created a black hole.

The black hole which has newly formed has belched a short-term yet amazing flash of gamma rays. These gamma rays are known as GRB: Gamma Ray Burst.

The flash of gamma rays disappeared after adequate view of seven seconds, however other longer wavelengths of light caused because of explosions like x-ray, visible light and radio continue to appear and shine for some weeks. The appearance of these rays for a long time made it possible for the astronomers to explore and study the aftermath of GRB 161219B, along with several of the ground-based observatories.

ALMA: Atacama Large Millimeter Array possesses unique capabilities which facilitated astronomers to further study this explosion at millimeter wavelength and learn new information about this GRB also about its powerful jets size.

Tanmoy Laskar, an astronomer from the University of California said, “As ALMA appears in millimeter-wavelength light, it carries information related to jet, how jets interact with dust and gas present in its surrounding, it is an important probe related to violent cosmic explosions like these.

These observations made it possible for astronomers to present with ALMA’s first-time lapse movie related to a cosmic explosion. It reveals an amazing long duration reverse shockwave caused by the explosion which echoed back through the jets. Laskar said “With the present understanding of GRBs we would expect a reverse shock will last for just a few seconds. But this one lasted for a whole day and that too in a good portion.

When a material blast away from GRB through its jets and runs into the gas present in its surrounding it leads to reverse shock. The event makes escaping material slow down which in turn sends a shockwave back to the jet.

And as these jets do not last for more than some seconds similarly a reverse shock also does not last for long duration. But now it appears case is different.

Carole Mundell who is a co-author of this popular study said “For many decades astronomers believed that this kind of reverse shock would lead to a bright flash of light, which has been really hard to find until now despite constant efforts and searches. With ALMA observation we can say that we were not looking in the right place, and these millimeter observations have now become our best hope for catching the cosmic fireworks of such type.”