Gamma-Ray Bursts

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Gamma-Ray Bursts

• Brian McBreen

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Short and Long GRBs

• Short GRBs (T90 lt 2s)
• Tend to be spectrally harder i.e. have a higher
  proportion of high-energy ?-rays relative to
  low-energy ?-rays

Long
Short

• Long GRBs (Tgt 2s)
• Tend to be spectrally softer i.e. have a higher
  proportion of low-energy ?-rays relative to
  high-energy ?-rays
• Originate from the collapse of massive stars

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How are GRBs detected?
Pandey et al 2006
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Tools of the Trade
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INTEGRAL GRBs

• INTEGRAL has detected 62 GRBs since launch in
• October 2002 up to January 2009
• 3 short GRBs
• 2 INTEGRAL GRB catalogues published
• (Foley et al. AA, 2008 Vianello et al. AA
  2009)
• 4 INTEGRAL GRBs have confirmed redshifts

Posters by Meehan et al. and Topinka et al.
GRB031203 z 0.1055 GRB050223 z
0.584 GRB050502a z 3.79 GRB050525a z 0.606
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Afterglow Statistics for INTEGRAL and Other
Missions (up to Feb. 2009)
BeppoSAX HETE-2 INTEGRAL Swift
GRBs 55 79 62 396
X-ray 31 19 22 339
Optical 17 30 20 206
Radio 11 8 8 24
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IBIS Sensitivity to Faint GRBs
Band et al. 2008
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GRB 041219a
McBreen et al. 2006

• Extremely intense burst
• Peak flux of 43 photons/cm2/s (20 keV 8 MeV)
• Emission up to a few MeV
• Good candidate for polarisation analysis
• Background events selected from a 240s interval
  occurring before GRB

SPI HK light curve of GRB 041219a (20 keV 8 MeV)
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Compton Scatter

• Photon with energy h? scattered by free electron,
  results in change of photon energy and momentum
• Between 300keV a few MeV, Compton is dominant
  for most elements

f
?
h?0
Ge (32)
h?1
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Polarisation Simulations for GRB 041219a

• Compared real data to simulated polarised and
  unpolarised data to obtain polarisation fraction
• Used spectral parameters (Band model) from real
  data to generate 100 polarised events

Image of coded mask (yellow) detectors (blue)
taken from simulations
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Polarisation with SPI
SPI can measure polarisation through multiple
events in its 19 detectors
120
60
0
180
Absence of detectors 2 17 removes 22 of pair
possibilities
240
300
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GRB041219a Results
Time Directions Polarisation Angle (deg)
12 sec 6 9653 6019
12 sec 3 9640 6012
Weighted mean of all results 60 at 2 s level
McGlynn et al AA 2007 and are in agreement with
Kalemci et al ApJ 2007
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IBIS Polarisation of GRB041219a
Gotz et al. 2009
Agreement between IBIS and SPI (McGlynn et al.
2007) for brightest 12 s interval.
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Polarisation with GRAPE
Toma et al. 2009
Simulated events that can be detected by GRAPE in
the Synchrotron with ordered field (red
circles), Synchrotron with random field (green
filled circles) and Compton Drag (blue plus
signs) models.
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Photoelectric Absorption - Theory

• Photon absorbed by the material
• Energy is transferred to an electron
• Electron is emitted
• Differential cross-section for an electron
• emitted from the s-orbital of an atom in
• the non-relativistic limit
• (R. Bellazzini et al. 2003)

f azimuthal angle of the emitted electron
-gt the emission angles are modulated by the
polarisation
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Polarisation with LEP
Toma et al. 2009
Simulated events that can be detected by LEP in
the Synchrotron with ordered field (red
circles), Synchrotron with random field (green
filled circles) and Compton Drag (blue plus
signs) models.
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GRB 090423
z 8.2
Most distant object ever observed
Salvaterra et al. 2009
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(No Transcript)
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GRB 080319B
The extremely luminous afterglow of GRB 080319b
imaged by the Swift X-Ray Telescope (left) and
Optical/Ultraviolet Telescope (right). Peak
apparent magnitude of 5.8 farthest object
observable with naked eye.
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Composite Light curve of GRB 080319b
Racusin el at. Nature (2008)
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AGILE GRB090510
Delayed gamma-ray emission from a short GRB
Giuliani et al. 2009
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Fermi GRB090510
New quantum gravity limit MQG / MPlanck
several Much stronger than previous best limit
of this kind from GRB080916c
Abdo et al. 2009
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Fermi GRB 080916c
Abdo et al. 2009
GBM and LAT lightcurves for the gamma-ray
emission of GRB080916c z 4.35 Most energetic
GRB detected 9 x 1054 ergs isotropic energy G
gt 1100
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Fermi GRB 080916c
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Fermi GRB090902b
Abdo et al. 2009
z 1.822
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Fermi - GRB090902b
New power-law component at high and low energies
(Abdo et al. 2009)
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X-Ray Afterglows
Gehrels et al. 2009
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Canonical X-ray Afterglow
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Swift X-ray Optical Afterglows
X-ray and optical lightcurves of GRB afterglows
in the Swift era
Gehrels et al. 2009
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Types of Optical Afterglows
Panaitescu et al. 2008
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Formation of Long GRBs
Gehrels et al. 2009
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GRB-SN Connection
Modjaz et al. 2006
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GRBs without Supernovae
GRB060505

• Lightcurves of SN 1998bw
• (GRB980425), SN 2002ap and
• SN 2006aj (GRB060218)
• Plotted as they would have
• appeared at redshift of GRB060505
• (top) and GRB060614 (bottom).
• Afterglow detections in each case
• plotted in black
• Neither GRB associated with
• significant SN emission down to very
• faint limits

GRB060614
Fynbo et al. 2006
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GRB Host Galaxies
Gehrels et al. 2009
A selection of the host galaxies of long-duration
(top row) and short- duration (bottom row)
gamma-ray bursts as imaged by HST.
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Host Galaxy Metallicities
Gehrels et al. 2009
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GRB Offsets from Hosts
Projected physical offsets for short GRBs (black)
and long GRBs (gray). The top panel shows a
cumulative distribution, while the bottom panel
shows the differential distribution.
Fong et al. 2009
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Conclusions

• Swift continues to drive major advances in
  Gamma-Ray Bursts including X-ray, Optical and
  Radio afterglows
• INTEGRAL has made major advances including
  polarisation (GRBs and Crab) and the faintest
  GRBs
• Major advances with AGILE and Fermi measure the
  GRB spectrum over 5 orders of magnitude in energy
  at the same time
• e.g. most luminous GRB
• QG limits
• Band Model new spectral features at high
  energies
• Band Model Power law component at high and
  low energies
• Need to plan and deliver new missions e.g. GRI,
  GRIPS etc.

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References

• Book on GRBs written by G. Vedrenne and J.L.
  Atteia (Springer)
• Recent review by N. Gehrels, E. Ramirez-Ruiz and
  D.B. Fox, Gamma-Ray Bursts in the Swift Era