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

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

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

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）

Gamma Ray Bursts (GRBs)  Time-scale: 0.1-100s  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: ~102-103  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

GRBs with Measured Redshifts Lloyd-Ronning et al. 2001 (astro-ph/0108200) Host galaxy Optical afterglow 15GRBs GRB 000131 z=4.50 No host galaxy is expected to be observed for GRBs at z>10 !

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

Afterglow GRB 000131 z=4.50 Ly Andersen et al. 2000

Afterglow K or L dropout Lamb & Reichart 2001

GRBs in H2 Molecular Clouds (Drain & Hao 2002) Lyman-Werner band absorption (11.26-13.6 eV at rest)

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

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

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

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

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

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

GRB000401

GRB000401 zl =50 zl = 30 zl = 10 zl = 5 Mlens=103M Lensed fitting 3σ 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

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)

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

Indicators for GRBs at z>10 Afterglow  No host galaxy observed  No optical afterglow: K or L dropout ( dust extinction)  H2 LW band absorption (11.26-13.6 eV at rest): high R observation  Weak dust, metal absorption

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