Scialog: Collaborative Teams - 2015
Catching the Emergence of a SN Years after the GRB
Supernovae, exploding stars which briefly generate more light than entire galaxies, are the most spectacular events in the cosmos since the Big Bang.
Astronomers and astrophysicists are interested in these massive explosions because they can reveal clues to the nature of matter, energy, gravity and associated phenomena that compose the physical universe.
Supernovae come in several types, depending on the makeup of the dying stars which produce them. Physicist Dimitrios Giannios, Purdue University, and astronomerLaura Chomiuk, Michigan State University, are studying “lc-type” supernovae. They are produced, according to theory, by the gravitational collapse of massive stars that have lost their outer layers of hydrogen and helium, and they make for very luminous explosions.
Some of these explosions are accompanied by a burst of gamma rays lasting from 10 milliseconds to several hours and putting out more energy than thousands of Earths vaporized in seconds. Gamma radiation consists of extremely high-energy photons, the elementary particles of all manifestations of electromagnetic radiation including light and radio waves.
“These gamma-ray bursts provide us with cosmological laboratories in which our theories for physics in extreme conditions can be tested,” say Giannios and Chomiuk.
They hope to detect a specific radio signature – that is, radio waves that turn brighter with time – theorized to be produced in the first few decades following a type-lc supernova (as opposed to other frequencies produced hundreds or even thousands of years after other types of supernovae).
This particular signal is thought to occur in the so-called coasting phase, the period when ejecta from the explosion sweep up material that initially surrounded the star – mostly gases and other molecules drifting in space — without slowing down. All of this material then becomes charged – ionized – by the strong interactions, as a result putting out specific electromagnetic signals of their own, including the radio signature Giannios and Chomick hope to see.
If they’re successful, detection of this signal will help to shed light on the fundamental nature of particle acceleration as well as the nature and density of gases and molecules surrounding massive lc-type stars before they go supernova. Subsequent calculations could also possibly confirm that a certain type of gamma radiation – called “long burst” – is closely associated with lc-type supernovae, thus allowing scientists to form a more accurate picture of what has been happening in the cosmos.
They plan to carry out their observations on eight different gamma ray bursts using two separate radio interferometers: the Karl G. Jansky Very Large Array in New Mexico for northern targets and the Australia Telescope Compact Array for southern targets. Radio interferometers consist of many antennae spread over a wide area that receive electromagnetic waves from a single source, allowing for high-resolution of distant objects.