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Hirotaka Ito RIKEN 2015 /2/13 Collaborators Shigehiro Nagataki (RIKEN), Jin Matsumoto (RIKEN), Shiu-Hang Lee (JAXA), Masaomi Ono (Kyushu Univ.), Jirong Mao (Kyushu Univ), Asaf Peer (UCC), Akira Mizuta (RIKEN), Alexei Tolstov (IPMU), Maria Dainotti (RIKEN), Shoichi Yamada (Waseda Univ.), Seiji Harikae (Mitubishi UFJ)

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Model for Emission Mechanism Internal Shock Model Photospheric Emission Model photosphereInternal shock External shock Low efficiency for gamma-ray production Clustering of peak enegy ~ 1MeV (e.g., Rees & Meszaros 2005, Peer et al.2005, Thompson 2007) flaw Natural consequence of fireball model High radiation efficiency Difficult to model hard spectrum in low energy band ()

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Difficulty in photospheric emission model f ~ 0 f ~ -1.2 non-thermal spectrum E (MeV) Broadening from the thermal spectra is required

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Dissipative process Giannios & Spruit 2007, Giannios 2008, 2012 Magnetic recconection Repeated Shock Ioka + 2007, Lazzati & Begelman 2010 Proton-neutron collision Derishev 1999, Beloborodov 2010, Vurm+2011 high energy tail is reproduced by the relativistic pairs produced by dissipative processes Beloborodov 2010 relativistic pairs upscatter thermal photons assumption 1D steady spherical outflow

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Geometrical brodening Structure of the jet can give rise to the non-thermal spectra Multi-dimensional structure of jet may be a key to resolve the difficulty Mizuta+2011 Ioka+2011 spectrum broadens even in the absence of relativistic pairs

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Our focus: Effect of the jet structure on the emission Find the jet structure that can explain the observation Stratified Jet structure ~1 photosphere 0 > 1 Accleration region Photons gain energy by crossing the boundary layer 2 effects on the spectra (I) multi-color effect (II) Fermi acceleration of photons Propagation of photons are solved by Monte=Carlo method f Spine Sheath see also Lundman + 2013

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r Spine (

r Spine (

DOP (I + - I - ) / (I + + I - ) d 0 =400 1 =100 multi-component jet that reproduces Band spectra High polarization degree (>10%) is predicted polarization obs (degree) 0% Future missions such as Tsubame and POLAR may probe such an emission See also Lundman + 2014

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L j = 10 50 erg/s j = 5 j = 5 = 500 16TI Woosley & Heger 2006 M * ~14Msun R * ~ 410 10 cm @presupernova phase Planck = inj >> 1 = 1 t=4s t=300s inj = 10 10 cm

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-2.5 -1 log =>

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-1 -2.5 log (t pre =2s pre = 3)

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Summary Structured jet can produce a power-law non-thermal tail above the peak energy - - Futrure works Photon accelerations in various structures with high spacial resolution calculation shocks, turbulence - Polarization signature is not negligible in the structured jet non-thermal particle is not required Multi-component jet can reproduce Band function irrespective to the observer angle is reproduced by the accelerated photons is reproduced by the multi-color effect High DOP (>10%) is predicted for the jet structure that reproduces Band function