Gamma-ray Bursts andParticle Acceleration

Katsuaki Asano(Tokyo Institute of Technology)

S.Inoue （ NAOJ ） , P.Meszaros （ PSU ）

Physical Condition in a Shell

R

ΔR=R/Γ2

Photons: Luminosity L

erg/s 10L ,300 cm,10 5214 R

In the comoving frame Energy Density: Magnetic Field:

erg/cc 1034

722

cRL

U

G 860081.0 UB

Time ScalesLet us consider a proton of 1019eV

In the comoving frame,7

2

19

106.3eV10

cmp

Dynamical Time Scale: sec 11/ cR

Acceleration Time Scale: sec 4.02

eBc

cm

cR pL

Cooling Time Scale: sec 18006

22

3

Bm

cm

eT

p

How to find evidence of proton acceleration?

Neutrinos

Neutrinos

Waxman and bahcall 1997, 1998

ｐ＋ γ→n+π ＋

π ＋→ μ ＋ +νμ

μ ＋ → e ＋ + νμ + νe

log [

E N

(E)]

1052erg x 100=500R=5 1014 cmB=0.1eat 1Gpcby 105 km2 detector

Kaon-decay

Pion-decay

Muon-decay

16 17 18 19 20-4

-3

-2

-1

0

1

2

3

4

5

-4

-3

-2

-1

0

1

2

3

4

5

Next talk -> Murase

Asano & Nagataki 2006

PhotonsSee e.g. Meszaros 2006, Dermer & Atoyan 2006

GRB spectrum

???

To catch the sign of proton acceleration

• GLAST will be Launched May in this year.• It will observe 10 MeV - 300 GeV photons.

TeV Photons

HESS

MAGIC

CANGAROO-III

Proton Cascade

ｐ＋ γ→n+π ＋

　　　　　　→ p+π0

Asano 2005

I.C.

E (eV)

E2N(E) [erg/cm2]

104 105 106 107 108 10910-5

10-4

10-3

Distortion due to proton cascade

s 1.1

100

erg 1051

t

E sh

Lepton distribution

E

Primary Electrons

Pairs from Cascade

fB=1.0

e-SY

Our Monte Carlo Simulation

Asano & Inoue 2007

Up=UefB=UB/Ue

I.C.

E (eV)

E2N(E) [erg/cm2]

104 105 106 107 108 109 101010-5

10-4

10-3

Deviation due to Inv. Comp.

s 33.0

100

erg 1050

t

E sh

fB=0.1

No sign of protonacceleration

Asano & Inoue 2007

e-SY

I.C.

E (eV)

E2N(E) [erg/cm2]

104 105 106 107 108 109 101010-5

10-4

10-3

Double break

s 12.0

300

erg 1051

t

E sh

fB=1.0

Characteristic Spectrum due to Protons

e-SY

I.C.

E (eV)

E2N(E) [erg/cm2]

Proton

Muon

Pion

104 106 108 1010 101210-6

10-5

10-4

10-3

Proton and muon synchrotron

s 033.0

1000

erg 1052

t

E sh

fB=30.0

e-SY

Proton acceleration efficiency

eV10@ 19

We need 6-8 1043 ergs/Mpc3/yr to explain UHECRs

epacc UU /ξ

See e.g. Murase, Ioka, Nagataki, Nakamura 2008

We may need Up/Ue>20. If GRB rate is 0.05 Gpc-3/yr, Up/Ue>100

We have assumed Up=Ue so far, but…

GRB rate

Much more protons are accelerated?

me/mp

Particle Number Distribution

Electron Proton

Energy (Arbitrary)0.0001 0.01 1 100

1e-06

0.0001

0.01

1 Acceleration

Larmor radius∝EJust behind the shock front

Much more protonsf() erg/cm2

Proton x10, p=2.5,Esh=1051 erg, t=0.1 s,=300, fB=1.0

Sync-e+ e-

IC-e+ e-

Sync-Sync-

[eV]100 103 106 109 1012

10-5

10-4

10-3

10-2

Asano, Inoue, & Meszaros in prep.

Proton=10 x Electron

Much more protonsf() erg/cm2

Proton x100, p=2.5,Esh=1051 erg, t=0.1 s,=300, fB=1.0

Sync-e+ e-

IC-e+ e- Sync-

IC-p

[eV]100 102 104 106 108 1010

10-4

10-3

10-2

Proton=100 x Electron

Photons from Proton cascade dominate.

See also Asano & Takahara 2003

Very Hard GRB

Kaneko et al. 2008

GLAST will find more such bursts ？

Esh-dependence

[eV]

f() [erg/cm2] Up/Ue=10, UB/Ue=1, t=0.1 s, =300

Esh=1049 erg

Esh=1050 erg

Esh=1051 erg

102 104 106 108 1010 101210-9

10-8

10-7

10-6

10-5

Up-dependence

[eV]

f() [erg/cm2] Esh=1051 erg, UB/Ue=1, t=0.1 s, =300

Up/Ue=10

Up/Ue=30

Up/Ue=100

102 104 106 108 101010-6

10-5

10-4

Γ-dependence

[eV]

f() [erg/cm2] Esh=1051 erg, Up/Ue=30, t=0.1 s, UB/Ue=1

103 106 109 101210-7

10-6

10-5

10-4

Hypernova

•Very bright supernova•Some associate GRBs•Progenitors may be massive stars (WR type?).•A stellar wind environment may exist around progenitors

Ejecta from hypernovae may be sources of 1017-1018eV CRs. (Wang et al. 2007)

Hypernovae are Sources of 1018 eV Cosmic Rays ？

1020eV

SNR ？

AGN? GRB?銀河団 ?

？？

Wang et al. 2007

Particle Acceleration in Winds

Faster, Energetically lower

[eV]

f() [erg/cm2]

Initial p (dashed)

Final p/n (solid)

(solid)(dashed)

p-SY

p-IC

Hypernova

100 105 1010 1015 102010-12

10-10

10-8

10-6

Secondary ParticlesAsano & Meszaros 2008

@100Mpc

～ 4 days integration

Secondary Photons

[eV]

f() [erg/cm2]

GLAST

-decay

p-SY-SY

e-SY

MAGIC

XMM-NewtonRegenerated Photon

100 105 1010 101510-9

10-8

10-7

10-6

～ 4 days integration

Regenerated Photons

GRBGamma-ray

IR background photons

e+ e-

CMB photons

Inv. Comp.

Razzaque et al. 2004

Summary

• GeV-TeV emissions due to protons in GRBs• Too much protons change spectra drastically• Secondary emission from hyeprnovae

– X-ray due to cascade from muon decay– GeV emission from proton synchrotron– “Delayed” TeV emission