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The biggest accelerators in space and on earth
chaired by Michelangelo Mangano (CERN), Antxon Alberdi, Silke Britzen, Greg Landsberg (Brown University (US)), Boris
Samuel Pioline (CERN), UlrikeWyputta from Monday, March 18, 2013 at 13:30 to Friday, March 22, 2013 at 18:30
Physical parameters of the
relativistic shells in the GRBs
S. Simić1, L. Grassitelli2 and L. Č. Popović3,4
1) Faculty of Science, Department of Physics, Radoja Domanovića 12, 34000 Kragujevac, Serbia
2) Argelander Institute fur Astronomie, Auf dem Hugel 71, D-53121 Bonn, Germany
3) Astronomical Observatory, Volgina 7, 11000 Belgrade, Serbia
4) Faculty of Mathematics, Department of Astronomy and Astrophysics, Studentrski trg 16, 11000 Belgrade, Serbia
Gamma-ray bursts: the most violent
explosions in the universe!
GRBs in short – observational facts
• The biggest accelerators in the Universe?
• Observed as a short and very intensive emission of radiation
• Broad emission band, from high energy gamma’s down to low
energy radio band
• Multi phase transition event
▫ Initial phase – gamma emission (longest < 1-2min)
▫ Afterglow – X-ray optical and radio domain
•
•
•
•
•
High temporal variability observed in the first phase
Homogenous distribution over celestial sphere
Afterglow with much less emitted energy
Rate approx. 1 GRB/day
Two sorties extracted T90 < 2s and T90 > 2s (BATSE team definition)
GRBs in short – observational facts
• The biggest accelerators in the Universe?
• Observed as a short and very intensive emission of radiation
• Broad emission band, from high energy gamma’s down to low
energy radio band
• Multi phase transition event
▫ Initial phase – gamma emission
▫ Afterglow – X-ray optical and radio domain
•
•
•
•
•
High temporal variability observed in the first phase
Homogenous distribution over celestial sphere
Afterglow with much less emitted energy
Rate approx. 1 GRB/day
Two sorties extracted T90 < 2s and T90 > 2s (BATSE team definition)
GRBs in short – observational facts
• The biggest accelerators in the Universe?
• Observed as a short and very intensive emission of radiation
• Broad emission band, from high energy gamma’s down to low
energy radio band
• Multi phase transition event
▫ Initial phase – gamma emission
▫ Afterglow – X-ray optical and radio domain
•
•
•
•
•
High temporal variability observed in the first phase
Homogenous distribution over celestial sphere
Afterglow with much less emitted energy
Rate approx. 1 GRB/day
Two sorties extracted T90 < 2s and T90 > 2s (BATSE team definition)
GRBs in short – observational facts
• The biggest accelerators in the Universe?
• Observed as a short and very intensive emission of radiation
• Broad emission band, from high energy gamma’s down to low
energy radio band
• Multi phase transition event
▫ Initial phase – gamma emission
▫ Afterglow – X-ray optical and radio domain
•
•
•
•
•
High temporal variability observed in the first phase
Homogenous distribution over celestial sphere
Afterglow with much less emitted energy
Rate approx. 1 GRB/day
Two sorties extracted T90 < 2s and T90 > 2s (BATSE team definition)
GRBs in short – what we conclude
• Homogenous distribution
• out of our galaxy
• galactic halo
• Detection of the afterglow
• measurement of redshift
• extragalactic
• High temporal variability
• constraints on the core size
• compact phenomena
• Two classes - progenitor type
• Long-soft bursts – collapsar model
• Short-hard bursts – NS-NS (NS-BH) merger model
GRBs in short – spectrum and energy
• Non thermal spectrum distribution
• two power law joined at the maximum energy
• max. energy change during the event
• constraints on the emission mechanism
• synchrotron, IC, synchrotron self Compton
• high and ultra high energy photons, MeVs and GeVs
• Total emitted energy
• enormous – even 1054 ergs
• constraints on form of ejected material – collimated or not?
GRBs in short – spectrum and energy
• Non thermal spectrum distribution
• two power law’s joined at the maximum energy
• max. energy change during the event
• constraints on the emission mechanism
• synchrotron, IC, synchrotron self Compton
• high and ultra high energy photons, MeVs and GeVs
• Total emitted energy
• enormous – even 1054 ergs
• constraints on form of ejected material – collimated or not?
Band et al., 1993.
GRBs in short – spectrum and energy
• Non thermal spectrum distribution
• two power law joined at the maximum energy
• max. energy change during the event
• constraints on the emission mechanism
• synchrotron, IC, synchrotron self Compton
• high and ultra high energy photons, MeVs and GeVs
• Total emitted energy
• enormous – even 1054 ergs in isotropic models
• constraints on form of ejected material – collimated or not?
GRBs in short – spectrum and energy
• Non thermal spectrum distribution
• two power law joined at the maximum energy
• max. energy change during the event
• constraints on the emission mechanism
• synchrotron, IC, synchrotron self Compton
• high and ultra high energy photons, MeVs and GeVs
• Total emitted energy
• enormous – even 1054 ergs
• constraints on form of ejected material – collimated or not?
Piran, T., 2005
GRB progenitors – long bursts
• Collapsar model:
• Death of massive star like supernova, but with creation of BH
• Material from star mantle swirl down toward the BH in a form
of high density accretion disc.
GRB progenitors – long bursts
• Conditions:
• Massive star > 40M sun – to create a BH
• Rapid rotation - to create accretion disc and pair of jets
• Low metallicity – to be stripped from the Hydrogen mantle
• Evidence:
• Long GRBs are found exclusively in star forming region
• For closer GRBs a supernova is detected immediately after
GRB event (GRB060218, GRB030329, GRB980425). But not
in all cases! Type I b/c have no hydrogen lines.
GRB progenitors – short bursts
• Hard for localization.
• Out of the star forming regions – in the outer
regions or even the outer halo of large
elliptical galaxies – not included in the star
formation process
• Most of the hosts galaxies are at low redshift
• Merger model – NS-NS or NS-BH
• NS-NS (NS-BH) in a binary system will loose
energy through gravitational waves
• The 2 objects will get closer until tidal forces
rip the NS apart and matter falls into a BH.
• The process has ms timescale
• Evidence – events located in the old galaxies
without star formation.
GRBs - shell interaction
• We propose following:
• Interactions are happen in the first phase of GRBs
• Produce the observed temporal variability of gamma
emission
• Stochastic process
• Put the constraints on the central engine –
relativistic flow of well defined collimated shells with
random parameters (masses, velocities, …)
• Interaction decelerate the shells
• Effect of accumulation of ejected material and it’s
shell interaction
• Main mechanism for observed variability
Relativistic shells - model
dR


• We apply a phenomenological model dt  c   1     1
• Evaluate a three main variables: R,  d
2 1

and m
dm
M ej  2(1   )m  m
• Material barriers are embedded into dm
R 2  dR
d 
 2nm p (1  cos  ) 3 3
 2R 
surrounding media
dt
  dt
dt 
• Mag. field in shell frame is the part of
total energy of the shell
s
• Homogenous distribution of
  R  Rc  2  
 R0  
n  n0 (4  3)  1  a  exp  
 
radiation over the shell
R
 b  
2

2

 
s
(
R 
B'  8B n0 m p c (4  3) 0  [1  a  e
 R
2
Huang , et al, 2000
Simić, et al., 2007
R  Rc 2
)
b
]
Relativistic shells - interaction
• Fitting of variety of different
pulses – longer or shorter
• FRED pulse shape – electron
cooling
Relativistic shells - interaction
• Fit in different BATSE channels
• Combined pulses generate
synthetic GRB light curve
• Parameters randomly chosen in a
given domain
GRBs – sample parameter distribution
• Constraints on GRB light curve selection:
• isolated pulses
• avoid small pulses – low temporal resolution
• different pulse shapes
• Selected pulses parameters FWHM, tpeak, Int and s
Simić - Popović, 2012.
Relativistic shells - parameters
Relativistic shells - parameters
param
0
Mej  10-10
[Ms]
b
n0 [cm-3]
m [rad]
Rc  1014 [cm]
Rc 
10-13 [cm]
nb  104
[cm-3]
max
125
25
90
110
0.1
5.5
30
335
min
62
0.9
43
10
0.04
1.2
2.2
0.6
mean
93
10
60
50
0.064
2.3
9.4
48
dev
13.5
7.6
9.6
19.4
0.014
1.6
5.0
52
GRBs – sample parameter distribution
• Some weak correlation between used
parameters can be extracted
GRBs – sample parameter distribution
• Stretch the model on the cases with two peaks combined
• Multiple interactions of shells with different velocities (Grassitelli at al)
• Expect even more constraints on the physical parameters of relativistic
shells
Grassitelli, et al
Thank you
References:
Piran, T., RvMP, 76, (2005), 1143.
Band , D. et al. (1993), ApJ 413, 281
Simić, S., A&SS, 309, (2007), 173
Simić, S, Popović, L. Č., (2012), 21, 3.
Grassitelli, L., 2013 in preparation