In: Physics
Why do astronomers think there are two basically different types of gamma-ray burst?
When astronomers looked at the number of bursts versus how long they lasted, they found two different classes of bursts: long-duration and short-duration. These two classes are likely created by different processes, but the end result in both cases is a brand new black hole.
Graph of the time versus number of bursts for the gamma-ray bursts observed by the BATSE instrument on the Compton Gamma-ray Telescope.
Long-duration bursts last anywhere from 2 seconds to a few hundreds of seconds (several minutes), with an average time of about 30 seconds. They are associated with the deaths of massive stars in supernovas; though not every supernova produces a gamma-ray burst.
Short duration bursts are those that last less then 2 seconds; lasting anywhere from a few milliseconds to 2 seconds with an average duration of about 0.3 seconds (or 300 milliseconds). These bursts appear to be associated with the merger of two neutron stars into a new black hole or a neutron star with a black hole to form a larger black hole.