From Central Engine to Gamma-Ray Emission for Long Gamma-Ray Bursts

Transcription

1 PACIFIC , at Moorea 31 Aug. 6. Sep From Central Engine to Gamma-Ray Emission for Long Gamma-Ray Bursts Astrophysical Big Bang Laboratory (ABBL, RIKEN) Shigehiro Nagataki Collaborators: Hirotaka Ito (ABBL, RIKEN) Jin Matsumoto (ABBL Leeds U.) Donald Warren (ABBL, RIKEN) Maxim Barkov (ABBL Purdue U.) Oliver Just (ABBL, RIKEN) Daisuke Yonetoku (Kanazawa U.) Kentarou Tanabe (a Company)

2 Gamma Ray Bursts Milky Way NASA Gamma-ray Sky (Repeated)

3 Counts of Gamma-rays observed by a satelite(cgro) Time (sec)) Gamma-Ray Bursts (Probably) The Most Powerful Explosion in the Universe

4 Distribution of Duration of GRBs Short GRBs Long GRBs Origin is Massive Star Explosion. Origin was unknown. Neutron Star Mergers!? ~10 sec ~1 sec Duration of Gamma-Ray Bursts (sec)

5 It was found that some Gamma-Ray Bursts were born together with Very Energetic Supernovae. SN1998bw Spiral Galaxy ESO 184-G82 (A.D. 1976) GRB was born together With SN1998bw (A.D. 1998).

6 Artistic Movie of a Long GRB From NASA HP

7 Schematic Picture of Long GRBs Shock Breakout Photospheric Emission?? Relativistic Jet Figure from P. Meszaros: Modified by S.N.

8 Central Engine of Long GRBs

9 Explosion Mechanism of GRBs is a Big, Unsolved Problem. BH or NS/QS? Neutrino or B-Field? Rotating Black Hole with Neutrino Heating? MacFadyen & Woosley 99, Popham+ 99, Surman & MacLauling 04, Chen & Beloborodov 07, S.N.+07, Lopez-Camara+09,10, Harikae+10, Taylor+11, Sekiguchi & Shibata 11, Zalamea & Beloborodov 11, Lindner+10,12, Levinson & Globus 13, Globus & Levinson 14, Batta & Lee 14, Nakamura+15, Rotating Black Hole with Strong B-Fields? Barkov & Komissarov 08, Komissarov & Barkov 10, Barkov & Baushev 11, Janiuk 13, S.N.09,11,13,18 Rotating Magnetars? Akiyama et al. 03, Thompson et al. 05, Burrows 07, Komissarov & Barkov 07, Bucciantini+09, Takiwaki 09, Metzger+11,15, Moesta et al. 14, Obergaulinger & Aloy 17, Obergaulinger+18, Rotating Quark Stars? See e.g. S.N for a review. Wang 00, Ouyed & Sannnino 02, Ouyed et al. 05, Berezhiani et al. 03, Paczynski & Haensel 05, Kosta et al. 14,.

10 Study on GRB Formation in Rapidly Rotating Massive Stars with Strong B-Fields S. N. (RIKEN) K. Tanabe (a Company) Tanabe and S.N. Physical Revier D, 78, (2008). S.N. Astrophysical Journal, 704, 937 (2009). S.N. Publication of Astronomical Society of Japan, 63, 1243 (2011). S.N. Cambridge Springs, Association of Asia Pacific Physical Societies (2013) S.N. Reports on Progress in Physics, 81, id (2018).

11 Kerr Black Hole Radius of Event horizon r H = a 2 Radius of Ergosphere Roy Kerr (1934- ) θ Schematic Picture of a Kerr Black Hole (from Wiki) r E = a 2 cos 2 θ In Boyer-Lindquist Coordinate a is Kerr Parameter 0 a 1 No Rotation Maximum Rotation

12 Penrose Process In ergosphere, Particles with negative Energy can exist. Roger Penrose (1931-) (E2) E0 = E1 + E2 E2 < 0 Thus, E1 > E0 (Gain of Energy = BH loses its Rotation Energy)

13 Blandford & Znajek Effect (1977) (Split-) Monopole Solution. Left:Roger Blandford Right:S.N. Efficient extraction of rotation energy of a black hole is possible, when slowly-rotating electro-magnetic (EM) fields are absorbed by a black hole that is rotating faster than the EM fields. C:Amplitude of B-Field. a: Kerr-Parameter. M: Mass of Black Hole. c=g=1 units

14 Blandford-Znajek Process can be seen Numerically Now Blandford and Znajek 1977 Red:Numerical Blue:Analytical (2nd order) Green:Analytical (4 th order) (Split-) Monopole Solution. Slow Rotation Fast Rotation C:Amplitude of B-Field. a: Kerr-Parameter. M: Mass of Black Hole. c=g=1 units Tanabe and S.N. PRD 2008

15 General Relativistic Magneto-Hydro-Dynamics (GRMHD) Code S.N. 09, 11, 13, 18, Mizuta, Ebisuzaki, Tajima, S.N.18, see also Gammie, McKinney, Toth 03, Basic Equations Additional Equations (Constrained Transport) Solver Flux term (HLL Method) Conserved Variables K-Computer (RIKEN) 10Peta-Flops Newton-Raphson Method Primitive Variables Slope (2 nd order in Space, 3 rd in time) Mimmod or Monotonized Center TVD Runge-Kutta

16 Simulation of Jet Formation by a Rotating Black Hole in a Massive Star C=G=M=1 Unit S.N ~600km ~15000km Density contour in logarithmic scale (g/cc) Dynamics is followed up to 1.77sec from the collapse.

17 Dependence of Dynamics on Rotating Black Hole a=0 No Rotation a=0.5 Mild Rotaion S.N a=0.9 Rapid Rotation a=0.95 Highly Rapid Rotation ~15000km Density Structure at T=1.6sec.

18 Blandford-Znajek Flux and Jet Energy S.N Faster is Better BZ (outgoing poynting)-flux in unit of 10^50 erg/s/sr at T=1.5760sec In logarithmic scale. a=0.95. ~12km Slow Rotation Fast Rotation Jet Energy at t= sec for a=0, 0.5, 0.9, 0.95 (Solid Curves).

19 3-Dimensional Simulation of Jet Formation in a Massive Star a=0.9 S.N. 2013, ~3000km

20 Split-Monopole Like Situation is Realized due to Gravitational Collapse! a=0.9 T~0.8sec Same Simulations. Left: 3D Image. Density+B-fields. Bottom: 2D Slice Density+Poloidal B-Fields ~150km ~150km

21 Amplification of B-Fields due to Rotation! a=0.9 T~0.85sec Same Simulations. Left: 3D Image. Density+B-fields. Bottom: 2D Slice Density+Poloidal B-Fields ~150km ~150km

22 Jet-Formation due to Blandford-Znajek Effect! a=0.9 T~0.9sec. Same Simulations. Left: 3D Image. Density+B-fields. Bottom: 2D Slice Density+Poloidal B-Fields ~150km ~150km

23 Origin of Time Variability of GRBs S.N.2009 Observation of a GRB Onset of the Jet Mass Accretion ~600km Density contour in logarithmic scale (g/cc) Time evolution of mass accretion rate at the horizon.

24 Why are GRBs Bright in Gamma-Rays?

25 Schematic Picture of Long GRBs Shock Breakout Photospheric Emission?? Relativistic Jet Figure from P. Meszaros: Modified by S.N.

26 GRBs shed light on The Ancient Universe Dark Age First Stars Recombination CMB GRBs may be useful to estimate the cosmological parameters.

27 The Yonetoku Relation (2004) Total citation is 426 (02 Aug. 2018) Ep Phenomenological Relation. It Makes GRBs Good Candles to Measure the Universe? Figures from Yonetoku-san s HP.

28 Models for Emission Mechanism of GRBs Internal Shock 〇 non-thermal spectrum? radiation efficiency hard spectra at low energy Photospheric Emission 〇 radiation efficiency In this talk, Yonetoku- Relation is well Reproduced. γ? non-thermal spectrum In this talk, non-thermal spectrum is well reproduced. γ photosphere Optically thick Internal shock Optically thin External shock

29 Monte-Carlo Simulations of Photon-Propagation For Photospheric Emission Model Ito, S.N., et al. ApJ 777, 62 (2013) Ito, S.N., Matsumoto, et al. ApJ 789, 159 (2014) Ito, Matsumoto, S.N., Warren, Barkov. ApJ 814, L29 (2015) Ito, Matsumoto, S.N., Warren, Barkov, Yonetoku, submitted to Nature Astronomy (2018). Hirotaka Ito Jin Matsumoto Shigehiro Nagataki

30 How to Make Non-Thermal Spectrum? Dissipative Processes (Shocks, Magnetic Reconnections, Proton-Neutron Flow): Pe er et al. 05,06, Ioka et al. 07, Levinson & Bromberg 08, Lazzati & Begelman 10, Budnik et al. 10, Bromberg et al. 11 Giannios 06,08, Giannios & Sprite 07, Chhotray & Lazzati 15 Beloborodov 10, Vurm et al. 11, Vurm & Beloborodov 15 Ito et al. 18, Superposition of Thermal Photons (Multi-Color Effects) & (Bulk) Inverse-Compton Morsony et al. 07, Lazzati et al. 09, Mizuta et al. 11, Nagakura et al. 11, Levinson 12, Lundman et al. 13, 14, Ito,SN et al. 13, 14, 15, 18, Lopez-Camara+14,

31 Reproduction of Non-Thermal Spectrum Numerical Set-Up for Monte-Carlo Calculations >> << >> 1 Ito, S.N. et al. ApJ Procedures: 1. We Consider a Stratified Jet (Spine- Sheath Structure): Steady, Analytic Flow. 2. Thermal Photons are injected at a deep region. 3. Photon propagation is solved taking into account Bulk-Compton Scatterings. Typical Spectrum of GRBs Multi-Color Effect Bulk- Compton Effect

32 A Big Jump in Bulk Lorentz Factor Generates HE-Gamma-Rays h 0 =400 q j =1 q 0 =0.5 q obs =0.4 Thermal + non-thermal tail c.f. GRB E max = G 0 m e c 2 Klein-Nishina cut-off Non-thermal tail becomes prominent as the relative velocity becomes larger

33 Sharp Structures are Necessary for Efficient Acceleration For an efficinet acceleration, Lorentz factor must vary by a few factor within dθ<<g -1 G 0 G 1 dq Physically, Sharp Structures are Required (see also Lundman, Pe er, Ryde 12). Numerically, Fine Resolution is Necessary. q

34 From a Stratified Jet to Multi-Component Jets G 0 =400 G 1 =100 dθ~0.2 β= -2.5 α=-1 dθ High energy spectra (β) is reproduced by accelerated photons By (Bulk) Inverse-Compton. Low energy spectra (α) is reproduced by multi-color temperature effect Multi-Color Effect Bulk- Compton Effect

35 Multi-Component Jet is Natural G 0 =400 G 1 =100 dθ Face on view of a jet Slice of the Jet Simulation by Jin Matsumoto (Leeds U.)

36 3D relativisitic hydrodymaical simulation Simulations of a relativistic jet breaking out of massive progenitor star g g t inj >> 1 t= 1 t=300s t=300s g g t=4s t=4s Progenitor star 16TI (Woosley & Heger 2006) M * ~14Msun R * ~ phase Jet parameter L j = erg/s q j = 5 G j = 5 Gh = 500 R inj = cm Radiative transfer calculation Model 1: steady injection Model 2: precession Propagation of Photons are Calculated using Monte-Carlo Method.

37 L j = erg/s θ = 5 gh = 500 t = 100s Background 3D Simulations of GRB Jet Propagation Steady injection Ito, Matsumoto, S.N.+15. Lorentz Factor log G precession t pre = 2s θ pre = 3 ローレンツ因子 log G

38 Model 1 steady injection log G 4 Acceleration of Photons are Seen in the Simulations! However Numerical diffusion smears out the sharp shock structure Efficiency of acceleration is artificially decreased α=-1 β=-2.5 Simulations with Finer Resolution are Necessary for the Next Step (Current Resolution is for (r, Θ, φ)).

39 Model 2 Precession (t pre =2s θ pre = 3 ) log G Precession Activities are Imprinted on Prompt Emissions. α=-1 β=-2.5 In Reality, such pulsation is not observed for a typical GRB. Severe Constraint Can be Drawn from Observations of Prompt Emissions!

40 The Yonetoku Relation (2004) Total citation is 421 (15 Feb. 2018) Ep Phenomenological Relation. It Makes GRBs Good Candles to Measure the Universe? Figures from Yonetoku-san s HP.

41 Jin Matsumoto Did Nice 3D GRB Simulations. J. Matsumoto (Leeds U)

42 Hirotaka Ito Did Nice Calculations of Radiation Transfer. H. Ito (ABBL, RIKEN) Schematic Pic. Of Radiation Transfer (Post-Processing)

43 Yonetoku relation was Reproduced: Evidence of photospheric emission! Ito, Matsumoto, S.N., Warren, Barkov, Yonetoku Natue Astronomy, submitted. H. Ito (RIKEN) J. Matsumoto (Leeds U)

44 Our Dream to Understand Long GRBs Shock Breakout Photospheric Emission?? Relativistic Jet Figure from P. Meszaros: Modified by S.N.

45 On-Going Project: Short GRBs

46 Gravitational Wave & Short GRB were Detected from the Neutron Star Merger (GW170817)! Fermi Satellite (Low Energy Gamma-Rays) Fermi Satellite (High Energy Gamma-Rays) INTEGRAL (Gamma-Rays) Artist s Image of a Neutron Star Merger forming a GRB. Time(sec) The GRB Occurred 1.7 sec after the Neutron Star Merger! LIGO (Gravitational Waves)

47 Was Origin of Short GRB Identified? Short GRBs Long GRBs Origin is Massive Star Explosion. Origin was unknown. This time, it is suggested that The origin is Neutron Star Mergers! ~1 0 sec ~1 sec Duration of Gamma-Ray Bursts (sec)

48 Simulations of Neutron Star Mergers T. Hatsuda (RIKEN). EOS in Neutron Star Matter K. Takami (Kobe / RIKEN) Y. Huang (RIKEN/PMO) L. Baiotti (Osaka U.) S.N. (ABBL, RIKEN) Takami, Rezzolla, Baiotti PRD (2015) Is Used as a template of GW signals From NSM (arxiv: ).

49 Theoretical Studies on Formation of Short GRBs Just+2016 Oliver Just (ABBL,RIKEN) Ito+2017 Hirotaka Ito (ABBL,RIKEN)

50 PI: Nagataki Astrophysical Big Bang Lab (ABBL). From 1 st Apr Current PDs: H. Ito, G. Ferrand, H. He, M. Ono, O. Just Students: M. Arakawa(Rikkyo/RIKEN), Y. Huang (PMO/RIKEN) Alumni: Lee(Kyoto), Tolstov(Kavli IPMU), Mao(Yunnan Obs.), Dainotti (Stanford), Teraki (Asahikawa), Takiwaki (NAOJ), Wada (Tohoku), Barkov (Potsdam/DESY), Wongwathanarat (MPA), Matsumoto (Leeds), Warren (ithems), Inoue (ithems) 2013, Aug , Sep Apr. 6

51 Summary Explosion Mechanism & Gamma-Ray Emission Mechanism of Long GRBs are Unkown (as well as Short GRBs) However, It was shown numerically that a rapidly-rotating black hole formed in a massive star with strong B-fields drives a Jet. It was shown numerically that more energetic jets are driven by more rapidly-rotating black holes. Time variabilities of the central engine may be the origin of time variabilities of GRBs. Also, Rotating BH with Strong B-Fields Looks Promising! Superposition of Thermal Spectrum & Bulk Inverse-Compton can Reproduce the Spectrum of GRBs very well. Multi-Component Jets in Prompt Emissions is Naturally Generated due to RT Instabilities. Yonetoku-Relation is well Reproduced (Evidence of Photospheric Emission Mechanism). Photospheric Model Looks Promising!