Transcript Gamma-ray Bursts - University of Pennsylvania

Gamma-ray Bursts
Presentation by Aung Sis Naing
A little bit about gamma-rays
How do you make gamma-rays?
What is GRB ?
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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
History
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In the early 1960s, the United States began
launching a series of top-secret satellites designed
to look for gamma rays emitted by nuclear bomb
tests (on the look out for Soviet nuclear testing in
violation of the atmospheric nuclear test ban
treaty).
Late 1960s ->detected bursts of gamma-rays
Several years -> gamma-ray bursts are coming
from space
They publicized the discovery in 1973.
Vela Satellites
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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
Mystery
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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 Xray bursts, came from explosive events
associated with neutron stars.
Compton Gamma-Ray Observatory
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NASA launched Compton
in 1991.
Carried an array of 8
detectors
Could determine the
direction of a gamma-ray
burst within about 1 deg.
Recorded about 1 per day
Even distribution across
the sky ->ruled out the
possibility that they come
from anywhere in the
Milky Way Galaxy.
GRB Distribution detected by
BATSE
Afterglow
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X-ray afterglow
detected by an Italian
satellite in 1997
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Visual afterglow
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Very bright
Theoretical Explanation
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Come from unusually powerful supernovae
An ordinary supernova that forms a neutron star
does not release enough energy to power the
luminosity of the brightest GRB’S.
A supernova that forms a black hole->more
matter into smaller region->more energy
 Hypernova
Suggestions
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A lot of literature related to GRB
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http://imagine.gsfc.nasa.gov/docs/science/kno
w_l1/grbs.html
GRB Clip
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http://imagine.gsfc.nasa.gov/Videos/news/GR
Bstar2.mov
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Thank you!
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Special Thanks to Online resources and The
Cosmic Perspective by Bennett, et al.
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Q&A