Jets in Gamma Ray Bursts Reem Sari . Caltech .

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Jets in Gamma Ray Bursts Reem Sari .
Caltech .
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Properties

• Duration 0.01-100s (bimodal)
• Isotropy Random direction
• 1 burst per day
• 300keV photons
• Non thermal Spectrum(very high energy tail, up
  to gt200MeV)
• short time scale variability (less than 10ms)

BATSE 1991-2000
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Temporal Variability

• dTlt1s, T100 ? NT/dTgt100

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COMPACTNESS PROBLEM g g ? e e-

• dT 1ms ? R lt 3107 cm
• E 1051ergs ? 1057 photonshigh photon
  density(many above 500 keV).
• Optical depth ?T n R1015gtgt1
• Inconsistent with the non thermal spectrum!

Spectrum Optically thin
Size Energy Optically thick
? Paradox ?
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Relativistic Time-Scales

• tB-tA R (1-?) / c R/2?2c
• tC-tA R(1-cos ?)/c R/2?2c
• tD-tA ?/c

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The SolutionRelativistic Motion

• Due to Relativistic Motion
• R g2 c dT
• Eph (emitted) Eph (obs) / g
• tgg g-(42a) nsTR 1015/g42a
• (Goodman Paczynski Krolik Pier Fenimore
  Woods LoebBaring Harding Piran Shemi
  Lithwick RS)

g gt 100
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Relativistic Motion
(Lithwick RS 2001)
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3) Kinetic Energy intoInternal Energy

• External Shocks
• Internal Shocks

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Temporal Variability

• dTlt1s, T100 ? NT/dTgt100

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Temporal Variability Models

• External Shocksirregular surrounding
• Simple Explosive Engine

• Internal Shocksmany colliding shells
• Complex, Long Lasting Engine

(RS Piran 97)
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Feb 28 1997
DRAMATICBREAKTHROUGH X-ray, Optical and Radio
counterparts were found Afterglow
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4 Stages
Coasting, ISGRB
Thermal acceleration
Early Afterglow FS RS
Deceleration Late Afterglow
Very Late Afterglow Newtonian
(Kobayashi, Piran RS)
Energy release
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Simple Theory

• Hydrodynamics deceleration of the
• relativistic shell by collision with the
  surrounding medium
• (Blandford McKee 1976 Meszaros Rees 1997
  Waxman 1997 RS 1997 Cohen, Piran RS 1998)
• Radiation synchrotron
• (Waxman, Mesaros Rees Katz Piran RS, Piran
  Narayan Granot, Piran RS)
• Clean, well defined problem.
• Few parameters
• E, n, p, ?e, ?B

Energy
Electron distribution
Magnetic field
Electrons energy
Density
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Theoretical Spectra
N(?e)
(RS, Piran Narayan 1998)
B
N(?e) ??e-p
cooling
?e
? B ?e2
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Theoretical Spectra
(RS, Piran Narayan 1998)
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Dynamics Radiation Light Curves
(RS, Piran Narayan 1998)
? ? game Ft???
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Observations vs. Theory
(Galama et. al., 1998 compared to RS, Piran
Narayan 98)
Good agreement between theory and observations
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Theory Observations
(Harrison et. al. Yost et. al.)
Good agreement between theory and observations
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Physical Parameters from the Observed Spectra

• The parameters E , n0 , ?e , ?B , p
• p the slope at high frequencies
• remaining parameter from ?a , ? m F?m , ?c
  (Wijers Galama 98 Granot, Piran RS 99)
• For GRB970508 we obtained E 5.3x1051
  ergs n0 5.3 cm-3 ? e 0.57
  ? B 0.0082
• This method is sensitive to the details of the
  model
• Can be applied at several epochs

4 observables 4 unknowns
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Physical Parameters from Broad Band fits
(Yost et. al.)
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Physical Parameters from Broad Band fits
(Yost et. al.)
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Radio Observations -Another confirmation of the
fireball model

• Radio observations of the afterglow of GRB970508
  (Frail et. al)
• Variability
• Scintilations (Goodman)
• Size after one month 1017cm.
• Rising Spectrum ?2 at low frequencies
• Self absorption (katz Piran)
• Size after one month 1017cm.

GRB 030329 is resolved vgtc

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Radio Images
SNR Cas A FRII Cyg A
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Implications of Jets

• Solid angle 2??2.
• Fj4?/2??2 200(?/.1)-2
• EtotEiso/Fb , Eiso4?D2.
• The real rate will be higher by Fj ????
• The energy in each burst is smaller by Fj.
• The total energy per galaxy is the same!

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Sidewise Expansion
(Rhoads Meszaros Rees RS, Piran Halpern)

• Fluid frame expansion c.
• Observer frame ?R?R/?.
• Initially ??0
• After 1/???0 ?1/?

tjet ?(tjet)1/?0
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Simple Scalings
(Rhoads Meszaros Rees RS, Piran Halpern)

• E ?2R3?c2 ?2
• Initially ??0 ?R-3/2 ?-1/2
• After tjet ?1/? ? decreases at constant R.

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Observed Jets
t-0.82
tjet1.2d
t-2.18
Harrison et. al. 1999
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Lightcurve BreaksSimultaneous at all frequencies

• F?? t-?
• ?gt?m F?? t-pt-2.2 ?? ? -1.1 optical, x
• ?alt?lt?m F?? t-1/3 ?? -5/6 IR, mm
• ?lt?a F?? t0 ?? -1/2 low radio
• The break is substantial at all frequencies.

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Prediction Rings
(Waxman RS Panaitescu Meszaros Granot, Piran
RS abc Granot RS)

• If a nearby GRB occurs it can be resolved.
  (redshift zlt0.1)
• High frequency narrow ring
• Low frequency disk with brighter edges.

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Achromatic Transition
tjet ?(tjet)1/?0

• Hydrodynamic transition.
• All frequencies should show a break at about
  the same time.

SUB MM
RADIO
OPTICAL
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Beaming Luminosity Relation
Frail et. al.
Afterglow - GRB correlation !
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Procedure to Estimate Energy

• Estimate K corrected Eiso
• Estimate break time tjet
• Use ??jet0.06 (tjet/1z)3/8 (Eiso/n)1/8
  (SPH)
• E?Eiso (?jet)2/2

We fixed n0.1
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GRBs Standard Candles !?
Luminosity distribution is spread over a factor
of 500 After correcting for beaming, spread lt10
4?D2F
Frail et. al.
2??2D2F
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GRBs Standard Candles !?
Total energy (including mildly relativistic
ejecta) is more standard than highly relativistic
energy.
2??2D2F
Berger et. al. 2003
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Amati et. al. Ghirlanda et. al.
But Nakar Piran Band Preece Friedman Bloom
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Liang Zhang 05
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GRBs Standard Candles !?
Total energy (including mildly relativistic
ejecta) is more standard than highly relativistic
energy.
2??2D2F
Berger et. al. 2003
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Standard EnergyorStandard EVERYTHING ?

• Viewing angle can mimic distribution of opening
  angles (Postnov et al)
• Standard energy dE/d? ? ?-2 (Rossi et al,
  mini jets Nakamura)
• Predicts the distribution ofopening angles and
  luminosity.Explains ?0.05 (Perna, RS Frail)

Correction to the energy but only little to the
rate
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Rate Energy Correction

• Assume luminosity function N?L-2
• Most bursts are weak.
• Total rate is that of the weak bursts!
• Assume energy is constant
• Weak bursts are not collimated.
• Most bursts need no correction.
• Due to increase of volume up to z1
• Typical angle 0.05
• Many of the observed bursts are highly beamed.
• There needs to be a correction of the energy.
• More sensitivity - Swift - larger typical angle.

Correction for the rate is small
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Jets Hydro - Open Issues

• At what rate the jet spread sideways?
• How much of the energy stay concentrated near the
  axis.
• Amount of break do not always agree with theory.
• Some numerical simulations suggest spreading is
  less pronounced that naïve one.

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Swfit X-rays fast-gtslow-gtfast
Barthelmy et. al
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Prompt/Continuous Energy Injection

• Power law distribution of initial Lorenz factors?
• Suggested by slow decays.
• A. Influences the dynamics (small gradual effect)
• B. Adds additional Emission site Long lived
  reverse shock.

(RS Meszaros)
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Magnetic field Direction

• Magnetic field buildup is NOT understood.
• Field compression Weibel instability suggests
  B?gtB??

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Fluctuations in Cylindrical Symmetry
(Gruzinov Waxman Medvedeve Loeb)

• Afterglow is a ring or disc.
• ltBgt has the same symmetry.
• lt ?gt0
• If B has fluctuation in size or direction then
  ??0.
• Small fluctuations coherent length small ?.

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Polarization by Fluctuations

• Maximal coherence length Completely random B.
  (Gruzinov Waxman)
• coherent cells grow at the speed of light R/? -
  comparable to fireball size.
• detailed calculation 50 coherent cells.
• ?70/?5010
• Coherence on skin depth size (Medvedev Loeb)
• negligible ?
• With scintillation ?1

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Break of symmetryBeamed Afterglow
(Gruzinov Ghisellini Lazzati RS)

• Assume ??B??/B??1
• Assume small coherence length(ignore
  fluctuations)
• Average over possible B directions (constrained
  by ?)
• Average over all emitting regions in jet geometry.

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B??gtB?
Direction of Polarization
B??ltB?
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High Prompt Polarization

• Coburn Boggs 021206 80 (But RutledgeFox)
• Willis et. al. 930131gt35 960924 gt50
• Uniform B
• Entangled B
• Only in the plane.
• Variation over 1/??
• Patchy shell model
• IC scattering (Eichler Levinson)

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Direction of Polarization B??ltB?
0
?0
? ?m/3
0
?0
? ?m
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Polarization Evolution
Offset0.95?0
Offset0.3?0
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Polarization Lightcurves
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Observations

• Radio upper limits
• 19 GRB 980329 (Taylor et. al.)
• 8 GRB 980703 (Frail et. al.)
• Optical upper limit
• lt2.3 GRB 990123 (Hjorth et. al.)
• First detection
• 1.7 for GRB 990510
• (Covino et. al. Wijerse et. al.)

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Observations

• Radio upper limits
• 19 GRB 980329 (Taylor et. al.)
• 8 GRB 980703 (Frail et. al.)
• Optical
• (Bjorsson 03)

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GRB 020813

• Spectral polarimetry with Keck
• Imaging polarimetry with VLT
• ? changes at fixed ?
• Inconsistent with randommagnetic fields
• Agrees well with jet interpretation.
• Polarization color?Perhaps in 021004.gtLy ?
  (Wang et. al.)Patchy absorber???

(Barth et. al.)
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GRB 030329
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GRB 030329
x t1.64
T (days)
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030329 - late radio optical break
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What did we learn from polarization?

• Significant change of polarization magnitude with
  little change in angle (020813 030329).
• Inconsistent with random patches.
• Suggest connection to global geometry.
• Low level of polarization ?3
• Entangled magnetic field
• Short coherence scale
• Almost random direction
• Suggests amplification by turbulence
• High level in prompt GRBs?
• Suggests different origin for B in prompt and
  afterglow.
• Change of 30 degrees in angle (030329)
• Suggests complex geometry, not single off axis
  jet.

Pachy shell (Piran) Mini jets (Nakamura)
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GRB to Afterglow TransisionGRB - Internal
shockAfterglow - Surrounding
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Prediction TransitionBurst Afterglow
(RS 1997)

• The initial external shocks (afterglow) may
  overlap the internal shocks (GRB) signal.
• Confirmation requires very early (10-100s)
  afterglow observations

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Reverse, Forward, Jets ...
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The Reverse ShockOptical Flash

• At tA EreverseEforwardEGRB
• ?m 1015Hz (?0/300)2
• ?c 1017Hz tA-1/2

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Predicted optical flash
? -rays
Reverse shock
forward shock
X -rays
optical
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ROTSE
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ROTSE
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ROTSE
So very bright! Could be seen with binoculars
from the other side of the universe!!!
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Reverse Shock in GRB 990123 - optical
reverse shock
forward shock
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Reverse Shock in GRB 990123 - radio
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Reverse Shock in GRB 990123

• Correct flash magnitude.
• Correct rise time.
• Correct rise rate.
• Correct decay rate.
• Correct radio flare.
• The ejecta is made of baryons!
• If n1 cm-3 then ?0200
• The equipartition parameters are similar in
  reverse and forward shocks.?

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The Hypernova Model (Zhang et. al.)