GRB a New Tool for the Study of the Universe Expansion
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Transcript of GRB a New Tool for the Study of the Universe Expansion
GRB a New Tool for the Study of the Universe
Expansion
Guido Barbiellini and Francesco LongoUniversity and INFN, Trieste
In collaboration with A.Celotti and Z.Bosnjak (SISSA)
Venice 24th February 2005XI International Workshop on "Neutrino Telescopes"
Outline Introduction
GRB phenomenology Prompt Emission and Afterglow GRB standard fireball model
GRB engine Energetics and Collimation Source models The fireworks model
Spectral Energy correlations Peak Energy vs Total energy correlations Reproducing the BATSE fluence distribution
GRB environment SN & GRB connection The Compton tail Recent experimental evidences
CGRO-BATSE (1991-2000)
CGRO/BATSE (25 keV÷10 MeV)
Gamma-Ray Bursts
Temporal behaviourSpectral shape
Spatial distribution
Costa et al. (1997)
BeppoSAX and the Afterglows
Kippen et al. (1998) Djorgoski et al. (2000)
• Good Angular resolution (< arcmin)• Observation of the X-Afterglow
• Optical Afterglow (HST, Keck)• Direct observation of the host galaxies• Distance determination
The Fireball Model
Cartoon by Piran (1999)
GRB progenitors
GRB 020813 (credits to CXO/NASA)
Afterglow Observations
Harrison et al (1999)
Achromatic Break
Woosley (2001)
Jet and Energy Requirements
Frail et al. (2001)
Jet and Energy Requirements
Bloom et al. (2003)
Collapsar model
• Very massive star that collapses in a rapidly spinning BH. • Identification with SN explosion.
Woosley (1993)
B field Vacuum Breakdown
Blandford-Znajek mechanism
Blandford & Znajek (1977)Brown et al. (2000)Barbiellini & Longo (2001)Barbiellini, Celotti & Longo (2003)
Vacuum Breakdown
Polar cap BH vacuum breakdown
Figure from Heyl 2001
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
Two phase expansion
Phase 1 (acceleration and collimation) ends when:
Assuming a dependence of the B field: this happens at
Parallel stream with
Internal “temperature”
collrand tt
3 RBcm109
1 R
acc301
1'
1
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.
Two phase expansion
Phase 2 (adiabatic expansion) ends at the radius: Fireball matter dominated:
R2 estimation Fireball adiabatic expansion
20 Mc
ERR
02 100RR
0
2'
'2
1R
R
The second phase of the evolution is a radiation dominated expansion.
Jet Angle estimation
Figure from Landau-Lifšits (1976)
Lorentz factors
Opening angle
Result:
The fireball evolution is hypothized in analogy with the in-flight decay of an elementary particle.
Energy Angle relationship
Predicted Energy-Angle relation
The observed angular distribution of the fireball Lorentz factor is expected to be anisotropic.
Spectral Energy correlations
Amati et al. (2002)Ghirlanda et al. (2004)
GRB for Cosmology
Ghirlanda et al. (2004)
GRB for Cosmology
Ghirlanda et al. 2005
Testing the correlations
(Band and Preece 2005)
GRB fluence distributionGRB RATESFR
Madau & Pozzetti 2000
zz
1)(R
dzdV
~dzdtdN GRB
FLUENCE DISTRIBUTIONUSING AMATI RELATION
By random extraction of Epeak (Preece et al. 2000) and GRB redshift for a sample of GRBs we reproduce bright GRB fluence distribution. Bosnjak et al. (2004)
Testing the correlations
Bosnjak et al. astro-ph/0502185
Testing the correlations
Bosnjak et al. astro-ph/0502185
Testing the correlations
Ghirlanda et al. astro-ph/0502186
SN- GRB connection
SN 1998bw - GRB 980425 chance coincidence O(10-4)(Galama et al. 98)
SN evidence
GRB 030329: the “smoking gun”?
(Matheson et al. 2003)
Bright and Dim GRB(Connaughton 2002)
Q = cts/peak cts
BRIGHT GRB DIM GRB
GRB tails
Connaughton (2002), ApJ 567, 1028 Search for Post Burst emission in prompt GRB energy
band Looking for high energy afterglow (overlapping with
prompt emission) for constraining Internal/External Shock Model
Sum of Background Subtracted Burst Light Curves Tails out to hundreds of seconds decaying as temporal
power law = 0.6 0.1 Common feature for long GRB Not related to presence of low energy afterglow
GRB tails
Sum of 400 long GRB bkg subtracted peak alligned curve
Connaughton 2002
GRB tails
Connaughton 2002
Dim Bursts
Bright Bursts
Bright and Dim Bursts
3 equally populated classes Bright bursts
Peak counts >1.5 cm-2 s-1 Mean Fluence 1.5 10-5 erg cm-2
Dim bursts peak counts < 0.75 cm-2 s-1 Mean fluence 1.3 10-6 erg cm-2
Mean fluence ratio = 11
Bright and Dim GRB
Q = cts/peak cts
BRIGHT GRB DIM GRB
The Compton Tail
Barbiellini et al. (2004) MNRAS 350, L5
The Compton tail
“Prompt” luminosity
Compton “Reprocessed” luminosity
“Q” ratio
Bright and Dim Bursts
Bright bursts (tail at 800 s) Peak counts >1.5 cm-2 s-1 Mean Fluence 1.5 10-5 erg cm-2
Q = 4.0 0.8 10-4 (5 ) fit over PL = 1.3
Dim bursts (tail at 300s) peak counts < 0.75 cm-2 s-1
Mean fluence 1.3 10-6 erg cm-2
Q = 5.6 1.4 10-3 (4 ) fit over PL =2.8
Mean fluence ratio = 11 “Compton” correction Corrected fluence ratio = 2.8 (z or
Epeak?)
R = 1015 cmR ~ R ~ 0.1
Recent evidences
Piro et al. (2005)
GRB 011121
Recent evidences
Piro et al. (2005)
GRB 011121
Effect of Attenuation
Epeak
Egamma
Ep ~ Eg0.7
Ep ~ Eg
Preliminary
Tau = 1.5 +- 0.5 Caution: scaling fluence and Epeak
Effects on Hubble Plots
Luminositydistance
Redshift
Reducing the scatter
Preliminary
Effects on Hubble Plots
Luminositydistance
Redshift
Preliminary
Conclusions
Cosmology with GRB requires: Spectral Epeak
determination Measurement of Jet
Opening Angle Evaluation of
environment material Waiting for Swift
results