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Kunihito IOKA (Osaka Univ.)1. Observation2. Fireball3. Internal shock4. Afterglow5. Jet
6. Central engine7. Links with other fields8. Luminosity-lag9. X-ray flash10. Summary
1. ObservationGamma-Ray Burst
Brightest object 15210 s ergsVela satellites in 1967
Origin has been a puzzle
~ 1000 events/yr
Angular distributionIsotropic
Luminosity
Time
GRB
Summary of observation
~ 1000 events/yrIsotropic, Inhomogeneous~ 200 keV10-3s ~ 103s : short, long
AfterglowX-rayOpticalRadio
Redshift
>msec
2. FireballCompactness problem
810 10ms cmR c T T 2 49
7 2810 ergE FD F D e e 2 22
133 2 7 210
10 erg cm 3Gpc 10msTe
FD F D TRR m c
Optically thick Non-thermal
MeVE
1Relativistic motion
2R E
N
MeV MeV
4 6.5B
210
FireballiRE
1 4 3 452 ,710 MeVi iT E R
3 3entropy const constT R
2exp 20keV:thine B pn m c k T T
9 1 4 1 452 ,76 10 cmi p i iR T T R E R
4 3energy const const iT R R R obs iT T T +Baryon
3bn R 14 1 2 1 2
52 21 10 cmthinR E
2E Mc
92 ,71 10 cm : Matter dominantmatter i iR R R 2E Mc
10 5 10
5
10 : Pure radiation 10 < <10 : Electron dominated1< <10 : Relativistic baryon <1: Newtonian
Thermal
Central engine
Optically thick region
Internal shocks
External shocks
?ISM
1Γ 1Γ eeγγ
Internal-External shock model
time
Luminosity Kinetic energy
Shock dissipation
3. Internal shock
r
Two shell collision
s m
rm sm mm
2 2
2
1 1
1
r r s s r s m m
r r s s
r s m m
m m m m E
m m
m m E
efficiency : 1 r s m
r r s s
m mm m
: 0.5 when 13.9r s r sm m
Kobayashi,Piran&Sari(97)
Many shell
4. Afterglow
r
External shock
m
rm sm mm
2m r s r rm m 34
3s pm R nm
2 3 2 243r r p rE m c R nm c
16 1 3 2 3 1 351 2 010 cmR E n
Hydrodynamics3 2 24
3 pE R nm c n
R3 8T
2T R
① Electron Fermi acceleration 2.21 , (Fermi acc.)e e e eU U O N
1B BU U O ② Magnetic field
Relativistic shock
n2 ,n U
2
2
4 3
1 p
n n
U nm c
Jump condition
Electron synchrotron emission1/3
F
22 2
22
43 8e T e
e ee
BF c
qBm c
5. 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
2 2T R
6. Central engine① Collapse of massive star
② Mergers of compact objects・Baryon free
・Location within host galaxies・GRB - Supernova (e . g . ,SN1998bw)?High ambient gas density
????
Collapsar, Hypernova
SN1998bw-GRB980425 46 65.5 0.7 10 erg/s : 10 dimL
Lightcurve Fe line
8. Luminosity-lag
X
Luminosity
Time
Time
TΔ
peakL
TΔ Lpeak ・Standard candle ?・Brighter than SNe Ia・Less extinction
ApJ,554,L163(01)
Thin jet
’’ ’
0 0 0ν
vv
v
j r, t A f ν t t r r
cos θ cosθ cosθH θ θ θ H cossinθ sinθ
EmissivityθΔ
vθ
Bβ -α /sα s’ ’
’’ ’0 0
ν νf ν =ν ν
BB1+
1+
~Band spectrum
B B1, 1, 2.5, s 1
Spectrum ’’fνν
’ν Bαν
2’
Bβν
2’
Pulse profile
Luminosity-width
FRED(Fast Rise Exponential Decay)
8232
.
obs
BκFWHM
peakν
κ: nobservatioακ where WFν
Viewing angle① Peak luminosity - spectral lag relation② Peak luminosity - variability relation③ Luminosity - width relation
GRB980425A typical GRB⇒ Association of GRBs with SNe