構造を持った相対論的ジェットからの光球面放射

Report
構造を持った相対論的ジェット
からの光球面放射
Hirotaka Ito
RIKEN
Collaborators
Shigehiro Nagataki (RIKEN), Jin Matsumoto (RIKEN),
Shiu-Hang Lee (JAXA), Masaomi Ono (Kyushu Univ.),
Jirong Mao (Kyushu Univ), Asaf Pe’er (UCC), Akira Mizuta (RIKEN),
Alexei Tolstov (IPMU), Maria Dainotti (RIKEN),
Shoichi Yamada (Waseda Univ.), Seiji Harikae (Mitubishi UFJ)
@コンパクト連星合体からの重力波・電磁波放射とその周辺領域2015 /2/13
Model for Emission Mechanism
Internal Shock Model
flaw
・Low efficiency for gamma-ray production
・Difficult to model hard spectrum in low energy band (α)
Photospheric Emission Model
Natural consequence of fireball model
(e.g., Rees & Meszaros 2005, Pe’er et al.2005, Thompson 2007)
・High radiation efficiency
・Clustering of peak enegy ~ 1MeV
γ
photosphere
γ
Internal shock
External shock
Difficulty in photospheric emission model
non-thermal spectrum
E (MeV)
Broadening from the thermal spectra is required
Dissipative process
high energy tail is reproduced by the relativistic pairs produced by dissipative
processes
Magnetic recconection
Giannios & Spruit 2007, Giannios 2008, 2012
Repeated Shock
assumption
1D steady spherical outflow
Ioka + 2007, Lazzati & Begelman 2010
Proton-neutron collision
Derishev 1999, Beloborodov 2010, Vurm+2011
relativistic pairs upscatter
thermal photons
Beloborodov 2010
Geometrical brodening
Structure of the jet can give rise to the non-thermal spectra
Mizuta+2011
spectrum broadens even in the
absence of relativistic pairs
Ioka+2011
Multi-dimensional structure of jet may be a key to resolve the difficulty
Our focus: Effect of the jet structure on the emission
Find the jet structure that can explain the observation
Stratified Jet structure
2 effects on the spectra
(I) multi-color effect
see also Lundman + 2013
(II) Fermi acceleration of
photons
Accleration
region
Photons gain energy by
crossing the boundary layer
photosphere
νfν
t~1
Spine
Sheath
G0 > G1
n
Propagation of photons are solved by Monte=Carlo method
Two-component jet
Spine
(θ<θ0 )
Sheath
(θ0<θ<θj )
Calculation Range
rin
rout (τ<<1)
= rs1
<< Rph
rout = 500Rph(τ~2×10-3)
:photospheric radius
rin (τ>>1)
r
h0
G
Fireball model
ri
G0
G1
h1
rs1
rs0
r
Two-component jet
Spine
(θ<θ0 )
Sheath
(θ0<θ<θj )
Initial Condition
Inject thermal photons at the
inner boundary
rout (τ<<1)
rin (τ>>1)
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
h0
G
Fireball model
ri
G0
G1
h1
rs1
rs0
r
Two-component jet
G0=400 qj =1° q0=0.5° qobs=0.4°
Thermal + non-thermal tail
Spine
Sheath
Emax = G0mec2
Klein-Nishina cut-off
Non-thermal tail becomes prominent as the relative
velocity becomes larger
-1 ~0.14°G -1
But limited only for narrow range of |θ
θ
|
<
G
obs
0
400
observer angle
Multi-component jet
G0=400 G1=100
β= -2.3
α=-1
dθ
Emax = G0mec2 ~ 100MeV
Interval of velocity shear dθ < 2G-1
high energy spectra (β) is reproduced by accelerated photons
Cut off at ~ 100 MeV
Low energy spectra (α) is reproduced by multi-color effect
see also Lundman + 2013
Multi-component jet
G0=400 G1=100
dθ
Face on view of jet
Simulation by Dr. Matsumoto
ジェットの断面
DOP(%)=(I+ - I-) / (I+ + I-)
polarization
multi-component jet that reproduces Band spectra
G0=400 G1=100
0%
dθ
qobs (degree)
High polarization degree (>10%) is predicted
See also Lundman + 2014
Future missions such as Tsubame and POLAR may probe such an emission
三次元相対論的流体シミュレーション
ジェットが大質量星の外層を突き破り、光学的に薄くなるまでの過程を計算
t=4s
g
g
親星モデル
16TI (Woosley & Heger 2006)
M* ~14Msun
R* ~ 4×1010 cm
@presupernova phase
ジェット
tinj >> 1
t= 1
t=300s
g
g
Lj = 1050 erg/s
qj = 5°
Gj = 5
Gh = 500
Rinj = 1010 cm
モデル1: 定常インジェクション
モデル2: 歳差運動
輻射輸送計算
光学的に十分厚い領域にPlanck 分布の光子を注入し、ジェットから解放され
るまでの過程をモンテ=カルロ法を用いて計算
モデル1 定常インジェクション
ローレンツ因子
log G
4°
光子は衝撃波領域を往復す
ることによってエネルギーを
得る。
現状
数値拡散によって衝撃波がなまってしまっている
=> 加速は弱まってしまっている。
α=-1
β=-2.5
モデル2 歳差運動 (tpre=2s θpre = 3°)
ローレンツ因子
log G
歳差運動の周期が光度曲
線にそのまま反映される
α=-1
β=-2.5
Summary
-
-
Structured jet can produce a power-law non-thermal tail
above the peak energy
non-thermal particle is not required
Multi-component jet can reproduce Band function irrespective to
the observer angle
β is reproduced by the accelerated photons
α is reproduced by the multi-color effect
Polarization signature is not negligible in the structured jet
High DOP (>10%) is predicted for the jet structure that
reproduces Band function
Futrure works
Photon accelerations in various structures with high spacial
resolution calculation
shocks, turbulence

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