Title: mssl astrophysics group
1mssl astrophysics group
Terribly hot stars.
g-ray sources, missions and stars
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Liz Puchnarewicz Mullard Space Science
Laboratory, UCL www.mssl.ucl.ac.uk/www_astro
2Terribly hot stars.
mssl astrophysics group
g-ray sources, missions and stars
introduction
g-rays
models
breakthrough
new missions
a brief history of g-ray astronomy and a look at
the g-ray universe
where do we see g-rays?
what does a g-ray burst look
like?
models collisions, hypernovae and others
Beppo-SAX, with backup from Hubble, makes a real
breakthrough
finding g-rays
mapping and measuring -
SWIFT and MSSLs UVOT
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3mssl astrophysics group
introduction
cosmic g-ray sources had been expected for
several years.
CR
g-ray
g-ray
Cosmic rays ISM
high-E electrons mag field
supernovae
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4mssl astrophysics group
Introduction
first crucial results
OSO-3
- First significant detection of g-rays from our
galaxy. - 621 cosmic g-rays
SAS-2
- SAS-2 (NASA) and COS-B (ESA)
- first mapped the g-ray sky
- detected the first point sources
COS-B
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5mssl astrophysics group
Introduction
first conclusions
1973 GRBs confirmed by SAS-2 and COS-B BUT
distance and origin were unknown SO energy in
burst unknown SO concluded that sources were in
our Galaxy, possibly reconnection of neutron star
magnetic field lines with the ISM magnetic field
(ie analogous to solar flares).
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6mssl astrophysics group
introduction
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7mssl astrophysics group
g-rays
- a g-ray burst occurs about three times a day
- in seconds-to-minutes, it emits more energy than
any other known phenomenon (apart from the Big
Bang) - they are distributed evenly over the sky
- they are very hard to study because they
disappear before you can catch them. - they are very, very hot
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8mssl astrophysics group
g-rays
So what are g-rays?
- Extragalactic in origin
- VERY energetic (up to 10 ergs) (only surpassed
by the Big Bang) - VERY quick (30msec to 1.6 hours) so must be
emitted from a region only a few 10s of
kilometres across
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9mssl astrophysics group
models
neutron star mergers
System emits radiation as neutron stars spiral
inwards. Merger occurs once every 10,000 to a
million years in a galaxy.
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10mssl astrophysics group
models
A popular model for the origin of g-ray bursts is
in the merger of two neutron stars.
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11mssl astrophysics group
models
the proton problem
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12mssl astrophysics group
models
black hole forms
Forms a black hole plus a disc
two stars collide
Relativistic jets emerge along disc axis
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13mssl astrophysics group
models where
they might come from
spatial distribution of counterparts
hypernovae
density of counterparts
coalescing neutron stars
distance from centre of host
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14mssl astrophysics group
Beppo-SAX
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15mssl astrophysics group
Beppo-Sax makes the breakthrough
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16mssl astrophysics group
Beppo-SAX Hubble
points to a galaxy
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17mssl astrophysics group
new missions
New campaign strategies - SWIFT
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18mssl astrophysics group
new missions
Once a burst has been detected, the telescope
will slew to position within seconds X-ray
positions to 2.5arcseconds UVOT positions to
0.3arcseconds
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19mssl astrophysics group
campaigns
Aims of the SWIFT mission
identify host galaxies uniquely by obtaining
arcsec positions measure redshift distribution
to determine energetics, cosmological evolution,
and GRB luminosity function locate GRBs
relative to host galaxies constrain burst
environment using X-ray absorption and optical
reddening
use optical/X-ray afterglow as high redshift
beacons measure Ly-alpha forest use X-ray
absorption to probe intergalactic/cluster medium
extend star formation rate observations to
high redshift
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20mssl astrophysics group
the end
start again
Liz Puchnarewicz Mullard Space Science
Laboratory, UCL www.mssl.ucl.ac.uk/www_astro