Astrophysicists look to the sky to study a variety of entities. There are familiar planets and stars, and the black holes and pulsars that are compelling due to their peculiar properties and behavior. But Aquib Moin is intrigued by transient objects that appear in the sky for seconds — and disappear.
Since the initial event is so short-lived, discovery and observation is a complicated process. NASA has satellites orbiting earth that scan the sky in search of GRBs. When a satellite observes a gamma burst, it sends a message to scientists on the ground who can direct terrestrial telescopes to the area of the sky where the burst was detected. This allows researchers like Moin to observe the lower-frequency remnants of GRBs — the "afterglow" — and the interaction this radiation has with the space around it.
On April 18, 2010, NASA's Swift satellite detected a GRB that lasted for about 20 seconds, but was observable from Earth for two and a half years at lower frequencies. Moin was granted telescope time by the Australia Telescope National Facility (ATNF) and US National Radio Astronomy Observatory (NRAO), which allowed him to observe the afterglow until it faded. His findings were published in the December 20, 2013, issue of The Astrophysical Journal.
Using these telescopes, Moin collected data and ran it through theoretical models designed to help researchers reconstruct the origin of GRBs — the models can also help researchers understand why some GRBs last longer than others. "These tools help us trace the possible sequence of events back in time based on the emission profile to see what might have happened with the initial burst and afterwards," Moin said. He believes that it is more likely that the GRB of April 18, 2010, was significant of an "exotic event like a star turning into a black hole."
But Moin acknowledges that there is much more work to be done: "The point is that these objects still hold a lot of mystery, and I have another GRB that I just detected at radio wavelengths in February 2014 that I am studying right now. When I have a sample of three or four sources like that, then I will be able to make more concrete statements."
This article originally appeared in NYUAD's 2013-14 Research Report (13MB PDF).
"When you go out and look at the sky, you see stars, planets, and galaxies, which remain observable for a long time. But there are also short-lived events, and their origin is still a mystery," said Moin, who is a postdoctoral associate in astrophysics at NYU Abu Dhabi working with Professor Ingyin Zaw. In particular, he is interested in gamma ray bursts (GRBs), which may be the result of catastrophic episodes, such as the birth or death of stars.
As their name suggests, GRBs are extremely powerful and bright bursts of high-frequency gamma rays. Most GRBs disappear in seconds. But others, as they grow older, emit radiation in lower frequencies, like X-rays, visible light, and radio waves. (Gamma rays have wavelengths that are about as long as the nucleus of an atom, while radio waves can have wavelengths measured in centimeters to kilometers.)
When you go out and look at the sky, you see stars, planets, and galaxies, which remain observable for a long time. But there are also short-lived events, and their origin is still a mystery.