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Photospheric emission from Structured Jet

Photospheric emission from Structured Jet. Hirotaka Ito. Collaborators. Shigehiro Nagataki YITP. Shoichi Yamada Waseda University. ＠ YITP Lunch Seminar 2012 5/30. Gamma-Ray Burst (GRB). Most luminous explosion in the universe. L γ,iso ~ 10 52 erg/s. ・ event rate. ~1000/yr. ・ duration.

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Photospheric emission from Structured Jet

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  1. Photospheric emission from Structured Jet Hirotaka Ito Collaborators Shigehiro NagatakiYITP Shoichi YamadaWaseda University ＠YITP Lunch Seminar2012 5/30

  2. Gamma-Ray Burst (GRB) Most luminous explosion in the universe Lγ,iso ~ 1052 erg/s ・event rate ~1000/yr ・duration Counts/s T ~ 10ms ー 100s ・rapid variability δt ～ ms Time (s)

  3. Prompt Emission Spectrum Band function Fν∝ν-α（hν< Ep） α~ -1 Fν∝ν-β（hν> Ep） β~ -2.5 Long GRB < Ep > ~ 160 keV <α>~ -0.9 ν^(-0.5) Short GRB ν < Ep > ~ 490 keV <α>~ -0.5 <β>~ -2.3 Briggs + 1999 Nava + 2011

  4. Model for Emission Mechanism Internal Shock Model ・Low efficiency for gamma-ray production flaw ・too hard spectrum in low energy band (α) Photospheric Emission Model (e.g., Rees & Meszaros 2005, Pe’er et al.2005, Thompson 2007) Ryde et al (2009) γ γ GRB090902B photosphere Internal shock External shock

  5. Model for Emission Mechanism Internal Shock Model ・Low efficiency for gamma-ray production flaw ・too hard spectrum in low energy band (α) Photospheric Emission Model flaw:high energy non-thermal tail（β） 低エネルギースペクトルを説明 (e.g., Rees & Meszaros 2005, Pe’er et al.2005, Thompson 2007) γ γ photosphere Internal shock External shock

  6. Present Study Photon acceleration in a structured jet as a mechanism for production of non-thermal tail Spine-Sheath jet G0 > G1 Photosphere τ~1 G0 >> 1 Spine Sheath G1>> 1

  7. Present Study Photon acceleration in a structured jet as a mechanism for production of non-thermal tail Spine-Sheath jet G0 > G1 Photosphere Accleration region τ~1 Photons gain energy by crossing the boundary layer G0 >> 1 Spine Sheath We solve the propagation of photons within the spine sheath jet G1>> 1

  8. Model Sheath (θ0<θ<θj ) Spine (θ<θ0 ) Velocity rout (τ<<1) Spine-Sheath Electron number density rin (τ>>1) Calculation Range rin << Rph rout = 500Rph(τ~2×10-3) r :photospheric radius

  9. Model Sheath (θ0<θ<θj ) Spine (θ<θ0 ) Velocity rout (τ<<1) Spine-Sheath Electron number density rin (τ>>1) Initial Condition Inject thermal photons at the inner boundary r Tin = 0.9 r81/6G4008/3 L53-5/12 (rin/1011cm)-2/3 keV Lin = 5.4×1052 r82/3G4008/3 L531/3 (rin/1011cm)-2/3 erg/s Propagation of photons are solved by Monte=Carlo method

  10. Result G0=400 qj =1° q0=0.5° qobs=0.3° Thermal + non-thermal tail Spine Sheath Emax = G0mec2 Klein-Nishina cut-off

  11. Comparison with Band function -1 β= -2.3 α= -1 α -2.3 β Structured jet model can reproduce Band function

  12. Summary - Structured jet can natural produce a power-law non-thermal tail above the peak energy - Band Spectrum can be reproduced Futrure works ・Photon accelerations in various structures multi-component, shocks, turbulence ・Evaluation of the polarization ・Hydrodymical simulation of relativistic jet as a background fluid

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