Transcript The GEANT4 toolkit and its application to the simulation

Gamma Ray Bursts:
a new tool for astrophysics and cosmology?
Guido Barbiellini
University and INFN Trieste
Outline
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Introduction
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The Fireball model
The Afterglow
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Internal shocks problems
The Progenitor
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External density
Iron lines
The Prompt Emission
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GRB and cosmology
Supranova
Collapsars
Cannonballs
The fireworks model
BeppoSAX Afterglow detection
HST host galaxies images
Gamma-Ray Bursts
Temporal behaviour
Spectral shape
Spatial distribution
CGRO-BATSE (1991-2000)
CGRO/BATSE (25 KeV÷10 MeV)
GRB: where are they?
The great debate (1995)
Fluence:10-7 erg cm-2 s-1
Distance: 1 Gpc
Energy:1051 erg
Distance: 100 kpc
Energy: 1043 erg
Cosmological - Galactic?
Need a new type of
observation!
BeppoSAX and the Afterglows
• Good Angular resolution (< arcmin)
• Observation of the X-Afterglow
Costa et al. (1997)
• Optical Afterglow (HST, Keck)
• Direct observation of the host galaxies
• Distance determination
Kippen et al. (1998)
Djorgoski et al. (2000)
GRB 021004: high precision radiography
of ISM from z=2.3
Schaefer et al. 2002
GRB host galaxies and Starburst galaxies
Berger et al 2002
GRB and Cosmology
Schaefer 2003
GRB and Cosmology
Djorgovski et al. 2003
The compactness problem
Briggs et al. (1999)
Light curve variability ~ 1 ms
Non thermal spectra
• Fluence (): (0.1-10) x 10-6 erg/cm2 (/4)
• Total Energy: E ~ 1051 ÷ 1052 erg
The compactness problem
Very High Optical Depth to pair production
Size
Pair fraction
Piran (1999)
Relativistic motion of the emitting region
The Fireball model
• Relativistic motion of the emitting region
• Shock mechanism converts the kinetic energy of the shells into radiation.
• Baryon Loading problem
External Shock
 Synchrotron & SSC
 High conversion efficiency
 Not easy to justify the rapid variability
Internal Shocks
 Source activity
 Synchrotron Emission
 Rapid time Variability
 Low conversion efficiency
The Afterglow model
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External Shock scenario
Forward + Reverse Shock
Jet structure confirmation
External density
Blast wave deceleration
Afterglow Theory
Sari, Piran & Narayan (1998)
Afterglow theory
Galama et al.(1998)
GRB 970228
GRB 970508
 Synchrotron Emission
 Power Law distribution of e-
Wijers, Rees & Meszaros (1997)
Afterglow Observations
GRB 990123
Akerlof et al. (1999)
Reverse shock flash
GRB 990510
Covino et al. (1999)
Optical Polarization
Afterglow Observations
• Radio Scintillation
GRB 970508
• Confirmation of Relativistic Motion
Frail et al. (1997)
Afterglow Observations
Harrison et al (1999)
Achromatic Break
Woosley (2001)
Jet and Energy Requirements
Frail et al. (2001)
Jet and Energy Requirements
Berger et al. (2003)
GRB 021004: surfing on density waves
Lazzati et al. 2002, Heyl and Perna 2002
Iron Lines
GRB 990705
Emission Lines
Amati et al. (2000)
Transient Absorbtion Line
Piro et al. (2000)
GRB 991216
Iron Lines theory
Vietri et al. (2001)
Iron Line Geometry
Internal Shock Scenario
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Prompt emission
Solve variability problem
Spectral evolution
Variability
Internal Shock variability
External Shock variability
GRB Light curve
Piran (1999)
Rise Time ~ Geometry of the Shell
Decay Time ~ Cooling Time
Norris et al. (1996)
Spectral Evolution
Spectral variability
Epeak
alpha
Preece et al. (2000)
beta
Progenitors
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Two populations of GRB?
Main models
Possible solution?
Progenitors
Long GRB
Short GRB
NS/BH Binary Mergers
Merging of compact objects (NS-NS, NS-BH, BH-BH).
These objects are observed in our Galaxy.
The merging time is about 108 yr, via GW emission.
Eichler et. al. (1989)
Collapsar model
Woosley (1993)
• Very massive star that collapses in a rapidly spinning BH.
• Identification with SN explosion.
Collapsar Model
Ramirez Ruiz et al. (2002)
Jets out of the Envelope
Paczynski (1998)
Supranova
Salgado et. al. (1994)
SupraMassive NS
Baryon Clean Environment
Vietri & Stella (1998)
Cannonball
Two stage mechanism
Dar & De Rujula (2000)
Towards a solution?
SN evidence
SN 1998bw - GRB 980425
(Galama et al. 98)
GRB 980326
(Bloom et al. 99)
Towards a solution?
Fruchter et al (1999)
Galama & Wijers (2000)
Offset from Host Galaxy
Star forming region density
Towards a solution?
Fryer et al. (1999)
Distance from Host Galaxy
GRB 011121: “evidence” for collapsar?
Bloom et al. (2002)
GRB 011211: “evidence” for supranova?
Reeves et al. (2002)
GRB 030329: the “smoking gun”?
(Zeh et al. 2003)
GRB 030329: the “smoking gun”?
(Matheson et al. 2003)
Vacuum Breakdown
Ruffini et al. (1999)
Charged BH
Magnetic Fields and Vacuum Breakdown
Blandford & Znajek (1977)
Brown et al. (2000)
Barbiellini, Celotti & Longo (2003)
Blandford-Znajek mechanism
The fireworks model for GRB
Guido Barbiellini (University and INFN, Trieste)
Annalisa Celotti (SISSA, Trieste)
Francesco Longo (University and INFN, Trieste)
Available Energy
The energetics of the long duration GRB phenomenum is compared with models of a
rotating Black Hole (BH) in a strong magnetic field generated by an accreting torus.
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Blandford-Znajek mechanism for GRB
54  M bh 
EBZ  0.3  10 

 M 

Blandford & Znajek (1977)
Brown et al. (2000)
Barbiellini & Longo (2001)
Figure from McDonald, Price and Thorne (1986)
Available Energy
A rough estimate of the energy extracted from a rotating BH is evaluated with a very simple
assumption an inelastic collision between the rotating BH and the torus.
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Inelastic collision between a rotating BH (10 M )and a massive torus
(0.1 M ) that falls down onto the BH from the last stable orbit
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Conservation of angular momentum:
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Available rotational energy:
Erot
I bhbh  I t t  I
3

1
I bh 
M bh
2 
3
2 


 I bh  bh 1 

2
M

1


bh
3 
bh 
2
I 
M 


 M 
M
3
3
Erot  2 M bh
2bh  3 t   3Erot ,bh t  M t c 2
M bh 8
 M bh 
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Available gravitational energy:
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Total available energy:
Egrav 
GM t M bh GM t M bh 1

 M t c2
Rbh
3Rbh
3
E  Erot  Egrav  1053 erg
Vacuum Breakdown
The GRB energy emission is attributed to an high magnetic field that breaks down the vacuum
around the BH and gives origin to a e fireball.
Pair production rate
Polar cap BH vacuum breakdown
Figure from Heyl 2001
Vacuum Breakdown
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Critical magnetic field:
Charge acquired by a
BH rotating in an external
magnetic field (Wald 1974)
Bc  4.5 1013 Gauss
Q  2BJ  2  1016 C
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Electric field:
E  2  10 V/cm
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Pair volume:
Vc  Rb3h
15
The formation of the fireball
The energy released in the inelastic collision is available to create a series of plasmoids
made of the pairs created and accelerated close to the BH.
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Pair density
(e.g. Fermi 1966):
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Magnetic field density:
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Energy per particle:
 0  acc104 erg
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Energy in plasmoid:
Eplasmoid  VcUB  1045 erg
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Number of plasmoids:
ne  81029 cm-3
U B  8 1025 erg cm-3
N plasmoid  B
E
E plasmoid
 B108
The formation of the fireball
After the formation of the plasmoid the particles undergo three processes.
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Acceleration time scale in E field: tacc
Particle collimation by B field:
Curvature radius:
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  3  106
tcoll
102accmec 2

 1019accs
eEc

acc 19


10 s
c sin  sin 
E (GeV )
cm
B(Gauss )
Randomisation time scale by Compton Scattering in radiation
field with temperature T0:
16
14
B 1
T0  
 
 8 a 
2
trand  10 accs
 1010 K
Two phase expansion
The first phase of the evolution occurs close to the engine and is responsible of energizing
and collimating the shells. It ends when the external magnetic field cannot balance
the radiation pressure.
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Phase 1 (acceleration and collimation) ends when:
Assuming a dependence of the B field:
this happens at R  108 cm
1
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Parallel stream with
1  30acc
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Internal “temperature”
1  1
'
trand  tcoll
B  R 3
Two phase expansion
The second phase of the evolution is a radiation dominated expansion.
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Phase 2 (adiabatic expansion) ends at the smaller of
the 2 radii:
E

Fireball matter dominated:

Fireball optically thin to pairs:
R  R0
14
Rpair
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R2 estimation R2  50R0
Fireball adiabatic expansion
Mc 2
 3E 

 R0 
 4R 3T 4 
0 p 

2' R2

'
1 R0
Jet Angle estimation
The fireball evolution is hypothized in analogy with the in-flight decay
of an elementary particle.
Figure from Landau-Lifšits (1976)
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Lorentz factors
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Opening angle
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Result:
Energy Angle relationship
The observed angular distribution of the fireball Lorentz factor is
expected to be anisotropic.
Predicted Energy-Angle relation
Conclusions
Andersen et al. (2000)
GRB: Gravity at Action
GRB 000131
GRB Cosmology