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

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

3. Central Region of GRB ?

4. Probing GRB Central Region

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

6. Rotational Energy of Kerr Black Hole

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

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

10. Data vs. Magnetar model (Lyons et al. 2008) We expect a relation between the pulsar initial spin period (P 0 ), dipole field strength (B p ), luminosity (L) and the characteristic timescale (T em ) for spin-down: L  B p 2 / P 0 4 and T em  P 0 2 / B p 2 (overestimated if final rapid decay due to collapse) B p (G) P 0 (msec) 10 16 10 15 Spin period too short? Too faint vs. X-ray plateau? B field too large or too brief? P. O’Brien, 2008 Nanjing GRB

11. III. Electromagnetic Vacuum Instability 3.1 QED e+ e- pair creation Schwinger 1951 Electric Effect: E 2 – B 2 > 0

12. 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

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

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

15. 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

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

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

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

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

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

21. Power from ergo region

22. 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 v acuum instability