(Review)

K. Ioka (Osaka U.)1. Short review of GRBs2. HE from GRB3. HE from Afterglow4. Summary

Gamma-Ray BurstBrightest object～ 1052 ergs s-1

Vela satellites (1967)

Origin has been a puzzle

200keV

GRB SpectrumBand spectrum

Non-thermal

200keV

Angular Distribution

                                                

                         

Isotropic

～ 1000 events/yr

Duration

Long-softShort-hard

Long burstShort burst

Discovery of Afterglow

X-ray

Radio

Beppo-SAX (1997)

Redshift

zmax=4.5

Optical → Redshift

Summary of Observation

Luminosity

Time

GRB～ 1000 events/yrIsotropic, Inhomogeneous～ 200 keV, Non-thermal103s ～ 103s : short, long

AfterglowX-rayOpticalRadio

Redshift

>msec

Standard Model

?optically thick

→e+e

Central Engine

Internal Shock

External shock>100

ISM

Luminosity

Time

GRBAfterglow

Kinetic energy↓

Shock dissipation

Afterglow Model

ｒｅｖｅｒｓｅ ｓｈｏｃｋｆｏｒｗａｒｄ ｓｈｏｃｋ

ISM Shock emission

① Electron Fermi acceleration 2 3

int 1 , ( >10 )e e e e eU U O N

int 1B BU U O ② Magnetic field

Internal energyKinetic energy intU

⇒ Synchrotron emission

Great Success of Model

Price et al.(03)

51-54

3

10 erg

0.01 100cm0.10.01

e

B

E

n

Fitting:

,max

, , ,

, , ,

as functions of time

e B

c m a

E n

F

Synchrotron shock model

Sari,Piran&Narayan(98)

Panaitescu&Kumar(00)

Galama et al.(98)

Optical Flash

Sari&Piran(99)

Zhang et al.(03)

ｒｅｖｅｒｓｅ ｓｈｏｃｋｆｏｒｗａｒｄ ｓｈｏｃｋ

ISM Shock emission

JetJet & Relativistic beaming

1・ Relativistic beaming・ Jet

1Γ

Jet in afterglow11 ΓθΓθθ ii ：ｓｉｄｅｗａｙｓ ｅｘｐａｎｓｉｏｎ

iθ

Energy, Event rate, Model

3 2 2 243 pE R nm c

3 8 1 2T T

Break in afterglowHarrison et al.(99)

3 8 1 8 1 8iso,520.057 dayt E n

Break time ⇒ Jet angle

Breaktime

Standard Total Energy

2 51iso 10 ergE E

Frail et al.(01)

Bloom et al.(03)

Smalldispersion

Massive Star Origin

Massive stellar collapse(Hypernova, Collapsar)

Binary NS merger

Supernova in afterglow

Bloom et al.(99)

Hjorth et al.(03)

1st example: SN1998bw-dim GRB980425

Position in host galaxyBloom,Kulkarni&Djorgovski(02)

GRB CosmologyMassive star origin High redshift GRBs⇒

Larson&Bromm(02) GRBQSO, galaxyGRBs are useful

for probing high z

Like QSOLike SNStar formationMicrolensingReionization…

Short Summary1.Cosmological (Long GRBs)2.Relativistic jet is ejected: >1003.Internal shock: GRB 4.External forward shock: Afterglow5.External reverse shock: Optical flash6.Synchrotron shock model succeeds7.Standard total energy (?)8.Massive star origin (Long GRBs)

But, …

Problems1.Fireball content: Kinetic or magnetic ?2.GRB emission mechanism: Synchro or not ?3.GRB jet structure: Uniform or not ?4.Jet acceleration: How to launch ?5.Environment: What is in front ?6.Shock parameters: Universal or not ?7.Short GRBs: What ?8.Other emissions: UHECR, HE, HE, GW ?9.GRBs & cosmology: How to use ?Etc…

GeV BurstsHurley et al.(94)

GRB940217

>10GeV photons can last for > 1hrGeV burst starts with MeV2% of total energy at 30MeV-20GeV

Earth occultation

18GeV

90min

GeV at 2.4s and 25sSpectral index –2 to GeV>MeV energy ～ <MeV one

Sommer et al.(94)

EGRET: 7GRB(100MeV<<18GeV)

Possible TeV Bursts

Atkins et al.(00)

Milagrito: Tentative (3) TeV detection in 54 bursts>50GeV fluence ～ 10×MeVbut no z

Tibet array (>10TeV): superpose 57 bursts: 6

GRAND (>10GeV): GRB971110: 2.7

Milagro (>100GeV): VHE fluence<MeV one

GRB970417a

a-ph/0311389

>MeV Tail in GRB941017

Gonzalez et al.(03)

One of 26GRBs

High energydecays moreslowly

Photon numberindex: -1 (hard)

Totani(00)

⇒ Nearby GRBs

Kneiske et al.(03)

103events/(3Gpc)3/yr～ 1event/(100Mpc)3/30yr⇒ Off-axis GRB ?

22

1IR IR, 1

0.1eV TeV

1 100 Mpce

T

m c

l n n

5GRB (z<0.5)

IR Background

Internal Shock

?optically thick

→e+e

Central Engine

Internal Shock

External shock>100

ISM

Luminosity

Time

GRBAfterglow

Kinetic energy↓

Shock dissipation

e± Pair CreationTarget photon energy

Cutoff energy

target

221TN

c t

Nphoton

～ 200keV

⇒⇒ Dim or long timescale bursts for TeV

＊ Scattering constraint is stronger if <mec2

TeVNtarget

target

Lithwick&Sari(01)

2 1target 2.5 TeV20 keV

1 652 2.5 21 GeVL t

Shock AccelerationTime scales

Maximum energy

① Acceleration time② Dynamical time③ Cooling time

⇒ ①Synchro ②SSC ③Proton synchro ④0 decay

2 2acc L e et r m c qB 2dynt R c t

26 1cool e T et m c B Y

20 1 2 1 2 1 2 152 2.5

14

1 220 1 4 1 4 1 4 5 2 1 252 2.5 2

10 eV

10 eV for electron

10 1 eV for proton

acc dyn e B

acc cool

e B

t t L

t t

L t Y

①

②

Vietri(95),Waxman(95)

Synchrotron

m

m max

max

∝e-p

∝e-p-1

∝e-2

∝(2-p)/2∝1/2

Electronenergyspectrum

Photonspectrum

Dim orlong burst:X-ray flash ?

3 2 1 2 1 2 2 152 2.5 2

1max 2.5

5 2 2 152 28

100 keV

10 1 GeV

10 erg cm s

m e B

m

L t

Y

F L D

Sari,Piran&Narayan(98)

F

eN

e

Synchrotron Self-Compton

Klein-Nishina:

∝1-p/2

∝1/2-p

∝1/2

2SSCe

F

SSCm SSC

KN maxSSCm

7 2 1 2 1 2 2 152 2.5 2e B L t

2 10 GeVSSCm m m

10 GeVSSCKN

max 100 TeVSSC

3 2 1 2 1 2 452 2.5 2e B L t

1 21 4 1 4 1 4 5 2 1 252 2.5 2 1e B L t Y

22SSCKN m em c

Guetta&Granot(03)

Synchrotron

SSC

SSC Luminosity

1

1syn eSSC e

syn B B B B

UU U YLYL U U U Y

1 2

if 1

if 1

e e

B B

e e

B B

Y

* For fast cooling, U ～ Usyn×ln (tdyn/tcool)1/2

(One zone)

SSC ～ Synchro

Sari&Esin(01)

Ioka(03)

Proton SynchrotronVietri(97),Totani(98)

1max, max, 2.510 1 TeVp

p ee

mY

m

m

e-synchrotronF

max, pmax,ep-synchrotron

1p

e

Y

dyn coolt t

proton injection fraction

3 2p

～ 1020eV protons emit

0 Decay0

0

,

, e

p n p

e

Waxman&Bahcall(97)Vietri(98)

15 1 2,MeV 2.50.1 10 eVp syn

N

F

1 ～ MeV ～ 1015eV

Synchrotron 0 decay

524

,MeV 2.5 2

0.2p pm

LRY Nt

GRB Spectrum

F Pair creation

MeV GeV TeV PeV

Electronsynchtrotron

SSCProtonsynchrotron

0 decay

External Shock

?optically thick

→e+e

Central Engine

Internal Shock

External shock>100

ISM

Luminosity

Time

GRBAfterglow

Kinetic energy↓

Shock dissipation

e,p-synchrotron & SSC

Zhang&Meszaros(01)

Long-dash: e-sy, short-dash: p-sy, dots: SSCTimes: trigger, 1 min, 1 hr, 1day, 1 monthE52=1, p=2.2, p=1, 0=300, z=1 flat

e=10-3, B=0.5n=100 cm-3

e=0.5, B=0.01n=1 cm-3

e=0.01, B=0.1n=1 cm-3

p-sy SSC e-sy

SSC vs p-synchrotron

Zhang&Meszaros(01)

(I’): SSC<p-syn(II’): SSC>p-synfor TeV

SSC dominatesin typical afterglow

Up ～ Ue,E52=1,n=1p=2.2,t=1hr

p-sy

SSC

,SSCc e

,SSCc e

0 Decay

Bottcher&Dermer(98)p-syn, p cascade, e+-syn, 0 decayLow energy: normalize to GRB970508 (z=0.83)E52=1, n=1 cm-3, 0=300, p=1, B=1, p=2Cascade emission decays more slowly than SSC(protons have less cooling)

E53=1,e=0.6,B=0.01,p=2.5 E52=1,e=0.6,B=0.01,p=2.5

E53=1,e=0.6,B=10-4,p=2.5 E53=1,e=0.6,B=0.01,p=2.2

f-synr-syn

solid: r-SSCdot: f-SSCdash-dot: f-IC of rdash: r-IC of f

10-100s:Reverseshockemission

Wang et al.(01)

4 IC in Early Afterglow

Off-Axis GRB

Ioka&Nakamura(01)

Fluence

Energy

-ray

X-ray

X-Ray Flash (XRF)

X-ray

-ray

Lamb et al.(03)

XRF ～ GRBexcept forsmall Epeak

& fluence

Distance Indicators

Sakamoto et al.(03)

Yonetoku et al.(03)

GRB spectrum

Energy

Peak Energy

XRF

We may selectnearby burstsquickly

SummaryIR background ⇒ Nearby bursts for TeVAfterglow is better than GRB for TeV High energy ～ Low energy

SSC, p-Synchrotron, 0 decay, etc. ⇒ Physical state, Lorentz factor, etc.

Nearby bursts ～ Off-axis ～ X-ray flash(?)Distance indicators Nearby bursts⇒