Gamma-ray Gamma-ray BurstsBursts

Presentation by Aung Sis NaingPresentation by Aung Sis Naing

A little bit about gamma-A little bit about gamma-raysrays

How do you make How do you make gamma-rays?gamma-rays?

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.

GRB Distribution detected GRB Distribution detected by BATSEby BATSE

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

Thank you!Thank you!

Special Thanks to Online resources Special Thanks to Online resources and The Cosmic Perspective by and The Cosmic Perspective by Bennett, et al.Bennett, et al.

Q & AQ & A