GRB accretion disks

1
GRB accretion disks

• Andrei M. Beloborodov
• Columbia University

2
Accretion Disks
3
Popham, Narayan, Woosley (1999) Kohri, Mineshige
(2001)
4
(No Transcript)
5
(No Transcript)
6
protons
Y -------------------------
e
protons neutrons
Beloborodov (2003)
7
Accretion disk models
Self-consistent disk model must
include feedback of
degeneracy on the cooling rate Cooling ?
low T ? degeneracy ? low positron density
? reduced cooling rate ?
higher T Regulation toward mild
degeneracy
8
Disk model

• - Vertically-averaged
• - Neutrino transport (escape probability)
• Full microphysics
• Advection of lepton number and heat included
• Fully relativistic (Kerr geometry)

W. Chen, A. M. Beloborodov
9
Jets
M87
10
Neutron-loaded jets

• Expansion and adiabatic cooling.
• 2. n-p decoupling and reheating (Rossi,
  Beloborodov, Rees 2005)
• Multi-GeV neutrino emission (Derishev,
  Kocharovsky, Kocharovsky
• 
  1999 Bahcall Meszaros
  2000)
• 3. Neutron-fed blast wave (Beloborodov
  2003)

11
GRB blast wave at the deceleration stage
12
GRB blast wave at the deceleration stage
16
R c 10 ( /300) cm
t G G
R 10 R
b b
n
n
b
trail
13
Summary GRB disks

• Neutrino-cooled at Mdot gt 0.01 Msun/s
• Neutrino-opaque at Mdot gt 0.1 Msun/s
• Equilibrium Ye Ye 0.1 for Mdot0.1
  Msun/s
• Ye 0.2 for
  Mdot1 Msun/s
• gt neutron-rich material
• Self-consistent disk model is obtained (Ye
  cooling rate hydro)
• --------------------------------------------------
  --------------------------------------------------
  --------------------------------------------------
  --
• Neutron-loaded jet links accretion physics with
  observed explosion