Kunihito IOKA (Osaka Univ.) 1.Observation 2.Fireball 3.Internal shock 4.Afterglow 5.Jet 6.Central...
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Transcript of Kunihito IOKA (Osaka Univ.) 1.Observation 2.Fireball 3.Internal shock 4.Afterglow 5.Jet 6.Central...
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