kunihito ioka (osaka univ.) 1.observation 2.fireball 3.internal shock 4.afterglow 5.jet 6.central...
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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 ergs
Vela satellites in 1967
Origin has been a puzzle
~ 1000 events/yr
Angular distributionIsotropic
Spatial distribution
3 2N P P Homogeneous in Euclidean
max 0.330 0.010V V
Inhomogeneous
Duration
Long-softShort-hard
Long burstShort burst
SpectrumBand spectrum
Non-thermal
AfterglowBeppo-SAX in 1997
X-ray
Radio
Optical → RedshiftRedshift
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 2
1010 erg cm 3Gpc 10msT
e
FD F D TR
R 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 dominated
1< <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 m
m m
: 0.5 when 13.9r s r sm m
Kobayashi,Piran&Sari(97)
Many shell
Time scale
2
c T
2 1310 cmR c T 1
2R
2
RT
c
Pulse width
22
c T
Pulse interval
T
Nakar&Piran(02)
4. Afterglow
r
External shock
m
rm sm mm
2m r s r rm m 34
3s pm R nm
2 3 2 24
3r 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
4
3 8e T e
e ee
BF c
qB
m c
Spectrum
,max
, , ,
, , ,
e B
a m c
E n
F
52
3
10 erg
0.1 50cm
0.1
0.01e
B
E
n
Collapsar, Hypernova
reverse shockforward shock
Shock emission
Optical flash
5. JetJet & Relativistic beaming
1・ Relativistic beaming・ Jet
1Γ
Jet in afterglow11 ΓθΓθθ ii :sideways expansion
iθ
Energy, Event rate, Model
3 2 2 24
3 pE R nm c
2 2T R
Total
Break in afterglowPolarizationA few %
Total energy
5110 ergE
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
Host galaxy
SN1998bw-GRB980425 46 65.5 0.7 10 erg/s : 10 dimL
Lightcurve Fe line
7. Links with other fieldsCR, HE, HE
44 3
19 21
10 erg/Mpc /yr
UHECR (10 - 10 eV)
Cosmology
8. Luminosity-lag
X
Luminosity
Time
Time
TΔ
peakL
TΔ Lpeak ・Standard candle ?・Brighter than SNe Ia・Less extinction
ApJ,554,L163(01)
Viewing angle of a single jet
?
?
?
⇒ Luminosity - lag relation ?
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 cos
sinθ 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’
20 0
ν 22 2
00
Δ T2cA r γF T = f νγ 1 βcosθ T
D γ 1 βcosθ T
cβwhere 1 βcosθ T = T T
r
Luminosity-Lag Relationv 0 1
v 2
1v
Lag:
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
9. X-ray flash
Off-axis GRB
Flux/Fluence RatioApJ,571,L31(02)
3 1 3 2 2 110 yr 5 3 10 yr Volume Viewing angle
10. SummaryGRB : Internal shockAfterglow : External shockJetViewing angle
Various relations, X-ray flashCentral engine ???
Collapsar? Merger?CR, HE, HE, GW, Cosmology