1. Center for Computational Physics
Can We Detect
First Gamma Ray Bursts ?
Masayuki Umemura
Center for Computational Physics
University of Tsukuba

2. How can we detect Pop III objects ?
1. Formation of Pop III stars ?
2. SN Explosions of Pop III stars ?
 First GRBs

3. GRB-SN Connection GRB030329/SN2003dh GRB980425/SN1998bw: Ic Hypernova
Kawabata et al. ApJ, 593, L19 (2003)
Mészáros, Nature, 423, 809

4. Heger et al. 2003, ApJ, 591, 288
Type I Collapsar: BH formation by core collapse
Type II Collapsar: BH formation by fallback caused by SN shock
Type III Collapsar: BH formation without proto-neutron star formation
JetSN: Hypernova
GRB: long GR burst（a portion of Jet SNs）

5. Gamma Ray Bursts (GRBs)
 Time-scale: s
 Energy:
~1052erg with a peak at ~0.1-1MeV(-ray)
cf Type II SN ~1051erg (Bolometric)
 Energy density: fireball energy density
~10-3 s after Big Bang (baryogenesis)
 Spectrum: featureless continuum (non-thermal origin)
 Event rate: 10-6/year/galaxy → 10-3/year/galaxy with beaming
 Variability: ~10-3 s → ~100km (relevant to BH or neutron star)
 Lorentz factor: ~
 Distribution: isotropic on the sky → cosmological source
 Afterglow: 10 s →  (X-ray, optical, radio)
identification of cosmological source
 Redshift determination: z4.5 as of now
500
600
700
800 5 10 15 20 25 30 s
GRB970508

6. GRBs with Measured Redshifts
Lloyd-Ronning et al (astro-ph/ )
Host galaxy
Optical
afterglow
15GRBs
GRB
z=4.50
No host galaxy is expected to be observed for GRBs at z>10 !

7. At z>10 50% (8/15) of GRBs can be detected by BATSE/HETE-2
detected by SWIFT
Lamb & Reichart 2001

8. Afterglow
GRB z=4.50
Ly
Andersen et al. 2000

9. Afterglow
K or L dropout
Lamb & Reichart 2001

10. GRBs in H2 Molecular Clouds
(Drain & Hao 2002)
Lyman-Werner band absorption ( eV at rest)

11. Empirical Indicators -ray Time lag - Luminosity relation t
Variability - Luminosity relation
X-ray t

12. GRB z-distribution (BATSE 112GRBs)
Cosmic SFR
GRB z-distribution (BATSE 112GRBs)
Schaefer et al. 2001
Steidel et al. 1999

13. Lloyd-Ronning et al. ApJ, 574, 554 (2002)
220 GRBs
L-V correlation

14. GRBs Lensed by Pop III Stars
collaboration with Y. Hirose, A. Yonehara, J. Sato
Image 1
GRB
Observer
Pop III Star
Image2
Time delay：
intrinsic
light curve
Image 1
lensed
light curve
Photon number
(Point mass)
Image 2 t

15. GRB 970508 (z=0.835) zl =50 Mlens=103M Intrinsic light curve
Artificially lensed light curve
500
550
600
650
700
750
800
850
120
122
124
126
128
130
132
134
time [s]
intrinsic lightcurve
1900
2000
2100
2200
2300
2400
2500
2600
2700
2800
2900
144
146
148
150
152
154
156
158
time [s]
lensed lightcurve
zl =50
Mlens=103M

16. Auto-correlation 1 (τ=64msn) lensed light curve C( ) I(t) τlens
τlens τ

17. GRB000401

18. GRB000401 zl =50 zl = 30 zl = 10 zl = 5 Mlens=103M Lensed fitting3σ
0.9995
Lensed
0.9995
0.999
0.999
fitting
0.9985
0.9985
-3σ
0.998
Intrinsic
0.998
0.9975
64ms
lens
0.9975
0.5 1
1.5 2
0.5 1
1.5 2
 [s] 1 1
zl = 10
zl = 5
0.9995
0.9995
0.999
0.999
0.9985
0.9985
0.998
0.998
0.9975
0.9975
0.5 1
1.5 2
0.5 1
1.5 2

19. Search for Lensed GRBs in BATSE Catalogue
Law data of 300 GRBs in BATSE catalogue are analyzed.
Results
GRB941202: a marginal candidate
V-L relation suggests z12 3σ
-3σ
τ=2.3s
τ=2.3s, z12  Mlens104M
(τ=2.3s, Mlens103M  z50)

20. Indicators for GRBs at z>10
Burst Event
Spectrum
 Lower energy band: -ray → X-ray: X-ray rich GRB (?)
 Weak Fe line emission
Lag & Variability
 Shorter spectral lag ( time dilation)
 Strong variability & longer variability timescale (e.g. 0.1s)
Empirical
 Low X=n /ep / t90
Gravitational Lens
 Bump in auto-correlation of light curve

21. Indicators for GRBs at z>10
Afterglow
 No host galaxy observed
 No optical afterglow: K or L dropout ( dust extinction)
 H2 LW band absorption ( eV at rest): high R observation
 Weak dust, metal absorption

22. Grazie tante