grb puzzles the baryon purity puzzle: why is the energy spend on gamma rays and not on expanding...
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GRB Puzzles
The Baryon Purity Puzzle: Why is the energy spend on gamma rays and not on expanding matter?
The photon entropy puzzle: Why Gamma Rays at 100 to 1000 KeV? Why not fewer photons at higher energy, or more photons at lower energy?
Why is what it is?
dM/dt scales as L5/3+… (Duncan, Shapiro, and Wasserman
1986, Woosley and coworkers 1996)…..
….but nearly linearly with Le+e- (Levinson and Eichler
1993):
Assume standing baryonic rarefaction wave at critical point:
Then
dM/dt = area x critical density x sound velocity
~ 1031 L51 9/8 g/s
TOO MUCH!
Possible answer to the Baryon Purity question:
All or nothing principle: Something must prevent baryons from emerging. (e.g. event horizon, bare strange surface, NS gravity)
This makes GRB particularly interesting. Perhaps they confirm Schwarzschild event horizons.
Neutron stars, strange stars might not need accretion disk but black hole MUST have accretion disk, and accretion disk must generate a baryonic wind
CONSEQUENCE OF ALL OR NOTHING PRINCIPLE:
ANY BARYONS IN GRB FIREBALL MUST HAVE ENTERED THROUGH THE SIDES
e.g. from exterior baryonic wind, walls of host star….
They typically do so after the fireball is already at high with violent consequences
Why Gamma Rays at 100 to 1000 KeV?
Possible Answers
Photosphere established by pair annihilation (Eichler and Levinson, 1999)
Neutron Leakage into Baryon-Pure Fireball
Baryon pure jet
Neutrons crossing B lines
High
1011 cm
1012 cm
Collisional Avalanche
n
nnn
Neutrons converted to protons + neutrons + pairs + neutrinos. This happens quickly, near the walls.
trigger Typical p for emergent protons is about 2
# neutrons that diffuse across is of order
(area/cross section)x(r/mfp)1/2 roughly 1050
Collisional Avalanche
n
nnn
Neutron free streaming boundary
Nn about A/
Neutron and ex-neutron mist
Nn about
A/about 1049A12
1) Pure Compton drag of pick-up ex-neutron gives
= [(3/4)(L/Ledd)(Rs/R) +o]1/3
(L/Ledd) about 1012 to 14 , (Rs/R) about 10-6
So or order 102 to 108/3
So what is ?
2) Gyration in Poynting flux gives naive estimate of
[1051 ergs/ 1049 Nnmc2]1/2 ~300
but significant transverse gradients and subsequent acceleration
3) Constrained Compton drag of walls: about or less than 1/sin, where is the angular size of the photon production region as seen at the point of last scattering ….
of order 102 ?
Thin pencil beam
Hollow cone
High polarization at
GRB Polarization by IC
(Eichler and Levinson 2003)
on the cone
dVmax/dcos(Eichler and Levinson, 1999)
GRB 980425 type events can be normal GRB, but expected to be rarely observed, because of small Vmax, despite large solid angle.
Note that
a) GRB 980425 did not have any significant flux above the pair production threshold. Scattered photons would not have pair produced with unscattered ones, even at large scattering angles
b) Scattering material is at r>30 lightseconds, and probably propagated from source. It has an edge.
Obscuration of scattered photons is not a necessary consequence of any assumptions of the model .
Distinguishing features of model:
1)Violent baryon loading allows extremely hard non-thermal spectra (even harder than shock acceleration). Multiscale baryon loading allows recycling of collisional byproducts, allowing extremely efficient UHE neutrino emission.
Distinguishing features of model:
1)Violent baryon loading allows extremely hard non-thermal spectra (even harder than shock acceleration). Multiscale baryon loading allows recycling of collisional byproducts, allowing extremely efficient UHE neutrino emission
2)Scattering off baryon-rich walls can account for GRB980425 and similar ones as scattered photons into off-axis viewing angle
Distinguishing features of model:
1)Violent baryon loading allows extremely hard non-thermal spectra (even harder than shock acceleration). Multiscale baryon loading allows recycling of collisional byproducts, allowing extremely efficient UHE neutrino emission
2)Scattering off baryon-rich walls can account for GRB980425 and similar ones as scattered photons into off-axis viewing angle
3) Positive polarization –intensity correlation expected if walls “sail” on Compton pressure. (Compton upscattering predicts negative correlation.)
Distinguishing features of model:
1)Violent baryon loading allows extremely hard non-thermal spectra (even harder than shock acceleration). Multiscale baryon loading allows recycling of collisional byproducts, allowing extremely efficient UHE neutrino emission
2)Scattering off baryon-rich walls can account for GRB980425 and similar ones as scattered photons into off-axis viewing angle
3) Positive polarization –intensity correlation expected if walls “sail” on Compton pressure. (Compton upscattering predicts negative correlation.)
4)Annular geometry can account for X-ray flashes and Amati et. al Eiso –peak correlation
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