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Title: mssl astrophysics group


1
mssl astrophysics group
Terribly hot stars.
g-ray sources, missions and stars
start
Liz Puchnarewicz Mullard Space Science
Laboratory, UCL www.mssl.ucl.ac.uk/www_astro
2
Terribly 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
bored
3
mssl 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
next
4
mssl 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
next
5
mssl 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).
next
6
mssl astrophysics group
introduction
back to menu
7
mssl 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

next
8
mssl astrophysics group
g-rays
So what are g-rays?
  1. Extragalactic in origin
  2. VERY energetic (up to 10 ergs) (only surpassed
    by the Big Bang)
  3. VERY quick (30msec to 1.6 hours) so must be
    emitted from a region only a few 10s of
    kilometres across

53
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9
mssl 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.
next
10
mssl astrophysics group
models
A popular model for the origin of g-ray bursts is
in the merger of two neutron stars.
next
11
mssl astrophysics group
models
the proton problem
next
12
mssl astrophysics group
models
black hole forms
Forms a black hole plus a disc
two stars collide
Relativistic jets emerge along disc axis
next
13
mssl 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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14
mssl astrophysics group
Beppo-SAX
next
15
mssl astrophysics group
Beppo-Sax makes the breakthrough
next
16
mssl astrophysics group
Beppo-SAX Hubble
points to a galaxy
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17
mssl astrophysics group
new missions
New campaign strategies - SWIFT
next
18
mssl 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
next
19
mssl 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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20
mssl astrophysics group
the end
start again
Liz Puchnarewicz Mullard Space Science
Laboratory, UCL www.mssl.ucl.ac.uk/www_astro
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