1. What GRBs can bring to Particle Astrophysics
(and vice-versa) ?
Bruce Gendre
LAM/OAMP

2. 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

3. 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

4. ms time variability : compact source
The fireball model
External
Shock
Rees & Meszaros 1992
Internal Shocks
Interstellar medium RS FS
1012 cm
1014 cm
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

5. ms time variability implies a compact object
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

6. Long GRB : death of massive star
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)

7. To sum up the problem
You observe this
And you want to know the detonator model and the color of the connectors

8. 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.

9. Neutrinos produced by GRBs
ANTARES Mediterranean Sea
Neutrinos can be produced by
The progenitor (like in SNe)
The acceleration process
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

10. 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 !

11. Previous observational evidences of high energy emission in GRBs:
High energy photons
Previous observational evidences of high energy emission in GRBs:
GRB (Hurley et al. 1994): detected by EGRET, with a 18 GeV photon;
GRB (Gonzalez et al. 2003)
GRB B (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 !!

12. GRBs can be used to study cosmology
GRB and cosmology
GRBs can be used to study cosmology
Distant events
Present empirical relations
Good complement to SNe
But…
No nearby event to calibrate any standard candle
Actual solutions
Do not care (may be problematic)
Use sample of same distant events (statistical significance still low)
Try to understand the empirical standard candles (complicated, but accurate)
redshift
Luminosity distance
Ghirlanda et al. 2004
GRBs
Supernovae

13. GRB, SNe, and CMB constraints are not similar
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)
SNIa
GRB
CMB
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

14. Afterglow cosmology : the Boër & Gendre relation
Relation linking the flux of X-ray afterglow with the date of the observation
Gendre, Galli, Boer 2008
After referee comments
Now 64 events
Broadening due to uncertainties on the prompt end
Gendre, Galli, Boer, 2008
Before referee comments
Now 8 outliers
Group xI
bright afterglows
Group xII
dim afterglows
Group xIII
Outliers
(GRB , , , )
Probability of spurious clustering : 3.6 x 10-8

15. 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

16. All these messengers arrive directly from the central engine
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 !!