(Review) K. Ioka (Osaka U.) 1.Short review of GRBs 2.HE  from GRB 3.HE  from Afterglow 4.Summary

Gamma-Ray Burst Brightest object ～ ergs s -1 Vela satellites (1967) Origin has been a puzzle

GRB Spectrum Band spectrum Non-thermal

Angular Distribution Isotropic ～ 1000 events/yr

Duration Long-soft Short-hard Long burst Short burst

Discovery of Afterglow X-ray Radio Beppo-SAX (1997)

Redshift z max =4.5 Optical → Redshift

Summary of Observation Luminosity Time GRB ～ 1000 events/yr Isotropic, Inhomogeneous ～ 200 keV, Non-thermal 10  3 s ～ 10 3 s : short, long Afterglow X-ray Optical Radio Redshift >msec

Standard Model ? optically thick  → e + e  Central Engine Internal Shock External shock  >100 ISM Luminosity Time GRB Afterglow Kinetic energy ↓ Shock dissipation

Afterglow Model ｒｅｖｅｒｓｅ ｓｈｏｃｋｆｏｒｗａｒｄ ｓｈｏｃｋ ISM Shock emission ① Electron Fermi acceleration ② Magnetic field Internal energyKinetic energy ⇒ Synchrotron emission

Great Success of Model Price et al.(03) Fitting: Synchrotron shock model Sari,Piran& Narayan(98)

Panaitescu&Kumar(00) Galama et al.(98)

Optical Flash Sari&Piran(99) Zhang et al.(03) ｒｅｖｅｒｓｅ ｓｈｏｃｋｆｏｒｗａｒｄ ｓｈｏｃｋ ISM Shock emission

Jet Jet & Relativistic beaming ・ Relativistic beaming ・ Jet Jet in afterglow ：ｓｉｄｅｗａｙｓ ｅｘｐａｎｓｉｏｎ Energy, Event rate, Model

Break in afterglow Harrison et al.(99) Break time ⇒ Jet angle Break time

Standard Total Energy Frail et al.(01) Bloom et al.(03) Small dispersion

Massive Star Origin Massive stellar collapse (Hypernova, Collapsar) Binary NS merger

Supernova in afterglow Bloom et al.(99) Hjorth et al.(03) 1st example: SN1998bw-dim GRB980425

Position in host galaxy Bloom,Kulkarni&Djorgovski(02)

GRB Cosmology Massive star origin ⇒ High redshift GRBs Larson&Bromm(02) GRB QSO, galaxy GRBs are useful for probing high z Like QSO Like SN Star formation Microlensing Reionization …

Short Summary 1.Cosmological (Long GRBs) 2.Relativistic jet is ejected:  >100 3.Internal shock: GRB 4.External forward shock: Afterglow 5.External reverse shock: Optical flash 6.Synchrotron shock model succeeds 7.Standard total energy (?) 8.Massive star origin (Long GRBs) But, …

Problems  Fireball content: Kinetic or magnetic ?  GRB emission mechanism: Synchro or not ?  GRB jet structure: Uniform or not ?  Jet acceleration: How to launch ?  Environment: What is in front ?  Shock parameters: Universal or not ?  Short GRBs: What ?  Other emissions: UHECR, HE, HE , GW ?  GRBs & cosmology: How to use ? Etc …

GeV Bursts Hurley et al.(94) GRB >10GeV photons can last for > 1hr GeV burst starts with MeV 2% of total energy at 30MeV-20GeV Earth occultation 18GeV 90min GeV at 2.4s and 25s Spectral index – 2 to GeV >MeV energy ～ <MeV one Sommer et al.(94) EGRET: 7GRB (100MeV< <18GeV)

Possible TeV Bursts Atkins et al.(00) Milagrito: Tentative (3  ) TeV detection in 54 bursts >50GeV fluence ～ 10×MeV but no z Tibet array (>10TeV): superpose 57 bursts: 6  GRAND (>10GeV): GRB971110: 2.7  Milagro (>100GeV): VHE fluence<MeV one GRB970417a a-ph/

>MeV Tail in GRB Gonzalez et al.(03) One of 26GRBs High energy decays more slowly Photon number index: -1 (hard)

Totani(00) ⇒ Nearby GRBs Kneiske et al.(03) 10 3 events/(3Gpc) 3 /yr ～ 1event/(100Mpc) 3 /30yr ⇒ Off-axis GRB ? 5GRB (z<0.5) IR Background

Internal Shock ? optically thick  → e + e  Central Engine Internal Shock External shock  >100 ISM Luminosity Time GRB Afterglow Kinetic energy ↓ Shock dissipation

e ± Pair Creation Target photon energy Cutoff energy N photon ～ 200keV  ⇒ Dim or long timescale bursts for TeV ＊ Scattering constraint is stronger if  <  m e c 2 TeV N target  target Lithwick&Sari(01)

Shock Acceleration Time scales Maximum energy ① Acceleration time ② Dynamical time ③ Cooling time ⇒ ① Synchro ② SSC ③ Proton synchro ④  0 decay Vietri(95),Waxman(95)

Synchrotron m mm  max max ∝  e -p ∝  e -p-1 ∝  e -2 ∝ (2-p)/2 ∝ 1/2 Electron energy spectrum Photon spectrum Dim or long burst: X-ray flash ? Sari,Piran &Narayan(98)

Synchrotron Self-Compton Klein-Nishina : ∝ 1-p/2 ∝ 1/2-p ∝ 1/2 Guetta&Granot(03) Synchrotron SSC

SSC Luminosity * For fast cooling, U  ～ U syn ×ln (t dyn /t cool ) 1/2 (One zone) SSC ～ Synchro Sari&Esin(01) Ioka(03)

Proton Synchrotron Vietri(97),Totani(98) e-synchrotron p-synchrotron proton injection fraction ～ eV protons emit

 0 Decay Waxman&Bahcall(97) Vietri(98) ～ MeV ～ eV Synchrotron  0 decay

GRB Spectrum Pair creation MeVGeVTeVPeV Electron synchtrotron SSC Proton synchrotron  0 decay

External Shock ? optically thick  → e + e  Central Engine Internal Shock External shock  >100 ISM Luminosity Time GRB Afterglow Kinetic energy ↓ Shock dissipation

e,p-synchrotron & SSC Zhang&Meszaros(01) Long-dash: e-sy, short-dash: p-sy, dots: SSC Times: trigger, 1 min, 1 hr, 1day, 1 month E 52 =1, p=2.2,  p =1,  0 =300, z=1 flat  e =10 -3,  B =0.5 n=100 cm -3  e =0.5,  B =0.01 n=1 cm -3  e =0.01,  B =0.1 n=1 cm -3 p-sy SSC e-sy

SSC vs p-synchrotron Zhang&Meszaros(01) (I ’ ): SSC<p-syn (II ’ ): SSC>p-syn for TeV SSC dominates in typical afterglow U p ～ U e,E 52 =1,n=1 p=2.2,t=1hr p-sy SSC

 0 Decay Bottcher&Dermer(98) p-syn, p  cascade, e + -syn,  0 decay Low energy: normalize to GRB (z=0.83) E 52 =1, n=1 cm -3,  0 =300,  p =1,  B =1, p=2 Cascade emission decays more slowly than SSC (protons have less cooling)

E 53 =1,  e =0.6,  B =0.01,p=2.5E 52 =1,  e =0.6,  B =0.01,p=2.5 E 53 =1,  e =0.6,  B =10 -4,p=2.5 E 53 =1,  e =0.6,  B =0.01,p=2.2 f-syn r-syn solid: r-SSC dot: f-SSC dash-dot: f-IC of r dash: r-IC of f s: Reverse shock emission Wang et al.(01) 4 IC in Early Afterglow

Off-Axis GRB Ioka&Nakamura(01) Fluence Energy  -ray X-ray

X-Ray Flash (XRF) X-ray  -ray Lamb et al.(03) XRF ～ GRB except for small E peak & fluence

Distance Indicators Sakamoto et al.(03) Yonetoku et al.(03) GRB spectrum Energy Peak Energy XRF We may select nearby bursts quickly

Summary IR background ⇒ Nearby bursts for TeV Afterglow is better than GRB for TeV High energy ～ Low energy SSC, p-Synchrotron,  0 decay, etc. ⇒ Physical state, Lorentz factor, etc. Nearby bursts ～ Off-axis ～ X-ray flash(?) Distance indicators ⇒ Nearby bursts