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What GRBs can bring to Particle Astrophysics
(and vice-versa) ?
Bruce Gendre
LAM/OAMP
The Gamma-Ray Burst phenomenon
Sudden and unpredictable bursts of hard X
and soft γ rays
• Typical durations of tens of seconds
• Cosmological origin
• Typical isotropic energy: 1051 to 1054 erg
Different and unclassifiable light curves
Non thermal and fast evolving spectra
• Described by an empirical smoothly
broken power-law (Band law)
• Peak energy of the νFν spectrum Ep
The Gamma-Ray Burst phenomenon
In 1997 BeppoSAX discovered a
fading emission following the
GRB (Costa et al. 1997)
• Observed at all wavelengths
(radio to X-ray)
• Detectable for days to weeks.
A burst : the sum of two
phenomena
• the classical GRB
phenomenon , the “prompt
emission”
• the subsequent fading
emission, the “afterglow
emission”
prompt
afterglow
The fireball model
Rees & Meszaros 1992
Internal Shocks
External
Shock
Interstellar
medium
RS
1012 cm
1014 cm
FS
1017 cm
ms time variability : compact source
huge amount of energy : plasma in ultra-relativistic ( > 100) expansion
kinetic energy loaded in relativistic electrons and magnetic fields (plus
few lost in fireball baryon load)
external layers of progenitor ejected as shells with different velocities :
Internal Shocks
Shells interaction with the external medium : External Shock
GRB progenitors
ms time variability implies a
compact object
Energy > ~1052 erg :
Stellar mass black hole
Forming a black hole
• Merging of two compact
objects : SHORT GRB (<2s)
• Gravitational collapse of a
massive star (M> 20 M) :
LONG GRB (>2s)
Woosley & McFadyen 1999;
Heger et al. 2001
Progenitor distance
Long GRB : death of massive star
• Possible early after big-bang
• Low metalicity environment
Distant events !
• Mean redshift ~ 2.5
(Jakobsson et al. 2006)
• Potentially the most distant
object visible within the
Universe
Short GRB : collapse of compact object binary
• Need to form the 2 compact objects (possible early after big-bang)
• Need to radiate binding energy (long time)
Nearby events !
Mean redshift ~ 0.5 (Ghirlanda et al. 2006)
To sum up the problem
You observe this
And you want to know the
detonator model and the
color of the connectors
Gravitational waves produced by GRBs
Gravitational waves can be produced
• Before the collapse of the binary progenitor (efficient)
• During the bounding of the core-collapse (inefficient)
Main target are short bursts
To date, no detection
Due to small volume
sampled (detection limit is
~ 100 Mpc)
z = 0.02
Z=2
Next step : advanced instruments,
LISA
• Should trigger on GRBs
• Will provide information on the
progenitor mass, geometry.
Neutrinos produced by GRBs
Neutrinos can be produced by
ANTARES Mediterranean Sea
• The progenitor (like in SNe)
• The acceleration process
p (n) 
   e  e 
Neutrino large observatories still
under construction / commissioning
/ calibration
• At the moment, no claimed
detection of neutrinos from GRBs
• Can give insights on the
progenitor and the acceleration
AMANDA/IceCube South Pole
Cosmic rays produced by GRBs
During the acceleration of the fireball, baryons, electrons and positrons
are accelerated up to relativistic velocities
• Possible candidate to produce energetic CRs
• But not clear if GRB produce detected CRs
To date, no
claimed detection
from any GRB
(but we detect only ~
40% of GRBs seen
on-axis, and none can
be seen off-axis !)
Work still is progress !
High energy photons
Previous observational evidences of high energy emission in GRBs:
• GRB 940217 (Hurley et al. 1994): detected by EGRET, with a 18
GeV photon;
• GRB 941017 (Gonzalez et al. 2003)
• GRB 090514B (AGILE collaboration) : detected in the GRID,
work still in progress
However, no clear
idea of what happen
after a few MeV.
• Unknown
GRB sky above
100 GeV.
• Waiting for
GLAST !!
GRB and cosmology
GRBs can be used to study
cosmology
But…
Luminosity
distance
• Distant events
• Present empirical relations
• Good complement to SNe
Ghirlanda et al. 2004
GRBs
No nearby event to
calibrate any standard candle
Actual solutions
Supernovae
• Do not care (may be
problematic)
• Use sample of same distant
events (statistical significance
still low)
• Try to understand the
empirical standard candles
redshift
Prompt cosmology
GRB, SNe, and CMB constraints are
not similar
Strong constraint on the
cosmological parameters
(Ghirlanda et al. 2007, Firmani et
al. 2006b, Amati et al. 2008)
GRB
GRBs are visible up to large distance
• Good indicator of re-ionization state
(e.g. Totani et al. 2006)
• Information on metalicity at high
redshift (e.g. Kawai et al. 2005)
• Beacon for non-radiating material
within the line of sight, such as WHIM
• Set the death time of pop III stars
• Estimation of distance (Pelangeon &
Atteia 2008)
Pelangeon et al. 2006
Afterglow cosmology : the Boër & Gendre relation
Relation linking the
flux of X-ray
afterglow with the
date of the observation
Gendre,
2008
Gendre, Galli,
Galli, Boer,
Boer 2008
Before
refereecomments
comments
After referee
Now 64 events
Now 8 outliers
Group xI
bright afterglows
Group xII
dim afterglows
Group xIII
Outliers
(GRB 980425, 031203,
060218, 060512)
Broadening due to
uncertainties on the
prompt end
Probability of spurious clustering : 3.6 x 10-8
Estimation of the redshift
For GRBs of group xI and xII,
we can estimate the redshift
needed for being compliant
with the B&G relation
• Proof on the bursts defining the
relation
• Easy to do : we know the group
of each event
Very good matching between the
measured and estimated redshifts
• Deviation at low redshift
Method not valid for nearby GRBS (z < 0.5)
Uncertainty on the redshift is ~ 30 %, sometime more
Conclusions
GRBs can produce :
• Gravitational waves
• Neutrinos
• Ultra high energy photons
• High energy cosmic rays
All these messengers arrive directly from the central engine
• Strong constraints to be set on the central engine properties …
• But once the instruments will be powerful enough !
GRBs can also help with cosmology :
• Constraints on the cosmologic parameters
• Measurement of the distance
• Information on the date of re-ionization and formation of first stars
So please continue building new and larger instruments : we would
be very happy to have these information for our models !!