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Particle Creation in GRB Central Region Strong Gravity and Electromagnetic Field

2008 Nanjing GRB Conference June 23-27, 2008. Particle Creation in GRB Central Region Strong Gravity and Electromagnetic Field. Hyun Kyu Lee( 李賢揆 ) Hanyang University. I. Introduction. Gamma Ray Bursts(GRB). Isotropic distribution Cosmic distances Isotropic energy

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Particle Creation in GRB Central Region Strong Gravity and Electromagnetic Field

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  1. 2008 Nanjing GRB Conference June 23-27, 2008 Particle Creation in GRB Central Region Strong Gravity and Electromagnetic Field Hyun Kyu Lee(李賢揆) Hanyang University

  2. I. Introduction Gamma Ray Bursts(GRB) • Isotropic distribution • Cosmic distances • Isotropic energy • Burst duration T ~ ms – 100 s

  3. Central Region of GRB ?

  4. Probing GRB Central Region

  5. II. A model for GRB central engine • Black hole-Accretion disk • Magnetic Braking

  6. Rotational Energy of Kerr Black Hole

  7. rapidly declining LC Simple Exercise: black hole-accretion disk(Poynting-flux dominated flow) HKL, PRD 64, 043006(2001) H.Kim & HKL, JKPS 42, S40(2003) turn-off profile

  8. Ultra-Strong Magnetic Field • GRB : B ~ 10^{15} G • Magnetars : SGR(Soft Gamma Repeaters , AXP(Anomalous X-Ray Pulsars) : B > 10^{14} G • Radio Pulsars : B ~ 10^{12} G Magnetically dominated system: E^2 –B^2 < 0

  9. Data vs. Magnetar model (Lyons et al. 2008) P. O’Brien, 2008 Nanjing GRB Bp (G) Spin period too short? B field too large or too brief? 1016 1015 Too faint vs. X-ray plateau? P0 (msec) We expect a relation between the pulsar initial spin period (P0), dipole field strength (Bp), luminosity (L) and the characteristic timescale (Tem) for spin-down: L  Bp2 / P04 and Tem P02 / Bp2 (overestimated if final rapid decay due to collapse)

  10. Electric Effect: E2 – B2 > 0 III. Electromagnetic Vacuum Instability 3.1 QED e+ e- pair creation Schwinger 1951

  11. 3.2 Fermion Production with Pauli Interaction • Astrophysical environment with storng magnetic field is magnetically dominant : B^2 – E^2 > 0 No Schwinger process • Fermion with Magnetic Moment : Pauli Interaction

  12. Effective potential for uniform magnetic field Critical magnetic field : Magnetic Effect: B^2-E^2 > 0 HKL & Y. Yoon JHEP 03, 086(2007)

  13. HKL & Y. Yoon JHEP 03, 078(2007)

  14. IV. Neutrino Production in GRB Central Region Neutrino: 1. electrically neutral(beta decay) 2. massive(neutrino oscillation) 3. flavor mixing (neutrino oscillation) 4. Dirac or Majorana ? 5. magnetic moment ? 6. physics beyond standard model

  15. Theoretical and experimental bounds on neutrino magnetic moment • Critical magnetic field • Slow process • Continuous source of neutrinos • Production in mass eigenstate

  16. Model for neutrino magnetic moment Validity of effective theory for strong magnetic field • Neutrino production inside fireball • Neutrino emission in accretion torus

  17. V. e+e- pair production inside ergosphere in preperation Geometry around Kerr black hole with mass m and angular momentum J=am Event horizon Boundary of ergosphere Magnetically-dominated

  18. along the field lines  No Poyintng flux On equator plane inside ergosphere 1. f < 0 : magnetically dominated

  19. 2. non force-free equator: f > 0 E > EC pair creation of e+ e- accretion flow of particles in negative energy orbit. (plasma effect is not included)

  20. Power from ergo region

  21. Out Looks New Laboratory • Astrophysical Phenomena GRB, Magnetar…… • Compact Objects Neutron star ~ 10 km Black Hole ~ 1.5 km (horizon) and Extreme Environment Strong Magnetic Field: B > 10^{15} G Strong Gravity : horizon, ergosphere Particle creation: Electromagnetic vacuum instability

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