What is GRB ?What is GRB ?
are short-lived bursts of gamma-ray photons
last from a few milliseconds to several minutes
shine hundreds of times brighter than a typical supernova
they are (briefly) the brightest source of cosmic gamma-ray photons in the observable universe
HistoryHistory In the early 1960s, the United States began In the early 1960s, the United States began
launching a series of top-secret satellites launching a series of top-secret satellites designed to look for gamma rays emitted by designed to look for gamma rays emitted by nuclear bomb tests (on the look out for nuclear bomb tests (on the look out for Soviet nuclear testing in violation of the Soviet nuclear testing in violation of the atmospheric nuclear test ban treaty).atmospheric nuclear test ban treaty).
Late 1960s ->detected bursts of gamma-Late 1960s ->detected bursts of gamma-raysrays
Several years -> gamma-ray bursts are Several years -> gamma-ray bursts are coming from spacecoming from space
They publicized the discovery in 1973.They publicized the discovery in 1973.
Vela SatellitesVela Satellites
Launched by the US Air Force to verify the Nuclear Test Ban Treaty of 1963.
Sensitive to Gamma-Rays No test ban violations
were identified, but mysterious flashes of gamma-rays were detected outside the solar system.
The Vela 5A Satellite
MysteryMystery
Origin unknown -> Origin unknown -> Astronomers didn’t know if these bursts originated at the edge of our solar system, somewhere in our Milky Way Galaxy, or very far away.
Most astronomers assumed that GRB’S, like X-ray bursts, came from explosive events associated with neutron stars.
Compton Gamma-Ray Observatory
NASA launched NASA launched Compton in 1991.Compton in 1991.
Carried an array of 8 Carried an array of 8 detectorsdetectors
Could determine the Could determine the direction of a gamma-direction of a gamma-ray burst within about ray burst within about 1 deg.1 deg.
Recorded about 1 per Recorded about 1 per dayday
Even distribution Even distribution across the sky ->ruled across the sky ->ruled out the possibility that out the possibility that they come from they come from anywhere in the Milky anywhere in the Milky Way Galaxy.Way Galaxy.
AfterglowAfterglow
X-ray afterglow X-ray afterglow detected by an detected by an Italian satellite in Italian satellite in 19971997
Visual afterglowVisual afterglow
Very brightVery bright
Theoretical ExplanationTheoretical Explanation
Come from unusually powerful supernovaeCome from unusually powerful supernovae An ordinary supernova that forms a An ordinary supernova that forms a
neutron star does not release enough neutron star does not release enough energy to power the luminosity of the energy to power the luminosity of the brightest GRB’S.brightest GRB’S.
A supernova that forms a black hole-A supernova that forms a black hole->more matter into smaller region->more >more matter into smaller region->more energyenergy
HypernovaHypernova
SuggestionsSuggestions
A lot of literature related to GRBA lot of literature related to GRB
http://imagine.gsfc.nasa.gov/docs/http://imagine.gsfc.nasa.gov/docs/science/know_l1/grbs.htmlscience/know_l1/grbs.html
GRB ClipGRB Clip
http://imagine.gsfc.nasa.gov/http://imagine.gsfc.nasa.gov/Videos/news/GRBstar2.movVideos/news/GRBstar2.mov