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

How?

Possible answers:

Neutron leakage

Photon drag of walls

Why Gamma Rays at 100 to 1000 KeV?

Possible Answers

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

Probability of observing polarization > P, homogeneous distribution, Euclidian

geometry,

Compton Sailing

WALL

s = 1 / sin

In frame of sail, ’/2

e,p

Intensity

Polarization

Ring-shaped Source

The index k depends on details of detectability D

D prop to k

point source diskring

Dependence on Beaming Factor

Azimuthal overlap

Given geometry, dependence on

Compton sailing state

Polarization from scattering by geometrically THICK annulus

Eiso- peak correlation (Amati et al 2002, Atteia et al 2003)

Eiso proportional to peak2

Off-axis Viewing as Grand Eiso- peak Correlate

Viewer outside annulus

Pencil beam

annulus

Inside annulus

1 MeV10 KeV

GRB’sXRF’s

Reflection to Large Angles and GRB 980425

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

5?) Matter kinetic energy significant only because of baryon seeding. Baryon seeding increases with GRB duration t5/2. Afterglow efficiency may be an increasing function of duration. But we are not sure yet.