1. Gamma-Ray Burst Ring-shaped Jets And Their Afterglows Ming Xu Department of Astronomy, Nanjing University 2010.06.22 Gamma-ray Sky from Fermi: Neutron Stars and their Environment—Hong Kong Collaborators: Yongfeng Huang, Siwei Kong

2. Outline GRB jets Structure of ring-shaped jets Afterglows of ring-shaped jets Early rebrightening from ring-shaped jet Conclusions 2

3. Gamma-Ray Burst 3 Gamma-ray bursts are short and intense unpredictable flashes of gamma-ray photons.

4. Light curve of GRB-complicated Millisecond Stellar scale 4 Center star

5. Peculiar properties of GRB High redshiftGRB 090423z=8.2 Nearby GRBGRB 980425z=0.0085 High luminosityGRB 080607L iso =2.2×10 54 erg/s “Naked GRB”GRB 080319Bm V =5.3 Ultra-relativisticGRB 090510Γ>1200 High engrgy photonGRB 090902Bhν=33.4 GeV Huge isotropic energyGRB 080916CE iso =5.6×10 54 ergs 5

6. M ⊙ c 2 =1.8×10 54 ergs GRBsIsotropic energy (ergs) GRB 990123E iso =2.8×10 54 ergs GRB 000131E iso =1.8×10 54 ergs GRB 050904E iso =1.2×10 54 ergs GRB 080319BE iso =1.3×10 54 ergs GRB 080607E iso =1.9×10 54 ergs GRB 080916CE iso =5.6×10 54 ergs GRB 090323E iso =4.1×10 54 ergs GRB 090510E iso =1.1×10 54 ergs Amati 08,09,10; Ghirlanda 08,09,10 E iso VS M ⊙ c 2 6 Stellar scale

7. 1. GRB Jets 7

8. GRB Jet Beaming Angle Gao & Dai 2010 ~ 3.4° f -1 ~ 1100 8 Intrinsic energy

9. GRB Jet Models Uniform jet (UJ) Universal structured jet (USJ) Cylindrical jet (CJ) Gaussian jet (GJ) Two-component jet (TCJ) “Fan” shaped jet (FSJ) “Ring” shaped jet (RSJ) 9 θ jet

10. GRB Jet Models Uniform jet Universal structured jet Cylindrical jet Gaussian jet Two-component jet “Ring” shaped jet “Fan” shaped jet 10 jet Most familiar

11. GRB Jet Models Uniform jet Universal structured jet Cylindrical jet Gaussian jet Two-component jet “Ring” shaped jet “Fan” shaped jet 11 Not uniform

12. GRB Jet Models Uniform jet Universal structured jet Cylindrical jet Gaussian jet Two-component jet “Ring” shaped jet “Fan” shaped jet 12 jet

13. GRB Jet Models Uniform jet Universal structured jet Cylindrical jet Gaussian jet Two-component jet “Ring” shaped jet “Fan” shaped jet 13 jet

14. GRB Jet Models Uniform jet Universal structured jet Cylindrical jet Gaussian jet Two-component jet “Ring” shaped jet “Fan” shaped jet 14 jet narro w wide

15. GRB Jet Models Uniform jet Universal structured jet Cylindrical jet Gaussian jet Two-component jet “Fan” shaped jet “Ring” shaped jet 15 jet

16. GRB Jet Models Uniform jet Universal structured jet Cylindrical jet Gaussian jet Two-component jet “Fan” shaped jet “Ring” shaped jet 16 ring hollow

17. Granot 2005 GRB Jet Models 17

18. 2. GRB ring-shaped Jets If GRB jet axis is precessing around the spin axis, there may be produced a ring-shaped jet. Fargion et al. 2006 18

19. Aloy & Rezzolla 2006 Mizuno et al. 2008 Quasi ring-shaped Jet 19

20. Sketch of ring-shaped jet Xu et al. 2008a 20

21. Evolution of a ring-shaped jet Xu et al. 2008a 21 Inner edge Outer edge RSJ

22. Evolution of a ring-shaped jet Xu et al. 2008a 22 Inner edge Outer edge UJ

23. Evolution of a ring-shaped jet 23 ISM Afterglows ring

24. 3. Afterglow light curves of ring-shaped jet Xu et al. 2008a 24 ring UJ Line of sight on ring

25. Effect of parameters on LC (1) Xu et al. 2008a 25 magnetic energy fractionelectronic energy fraction opening angle of the central cone observing angle

26. Effect of parameters on LC (2) Xu et al. 2008a 26 Number density of ISMpower-low index of electron energy distribution

27. Afterglows LC of ring-shaped jet Xu et al. 2008a X-ray band Radio (8.5Ghz) band 27

28. R-band Fit to afterglow of GRB 050820A Xu et al. 2008b 28

29. 4. Rebrightening from ring-shaped jet Xu et al. 2008a On the ring In hollow cone 29

30. Rebrightening VS Flare Chincarini et al. 2007Margutti et al. 2010 >1 30 GRB 081028 t Δt

31. Rebrightening from off-axis model Margutti et al. 2010 31 GRB 081028 Line of sight Prompt emission?

32. Early rebrightening of GRB 070208 http://www.swift.ac.uk/xrt_curves/00259714/ 32

33. Compare to off-axis conical jet Line of sight The ring-shaped jet model is superior over the normal off-axis conical jet model when considering the production of the intensive γ-ray radiation in the prompt GRB phase. 33

34. Xu & Huang 2010 Early rebrightenings from ring-shaped jets 34 Line of sight in the central axis of hollow cone

35. Afterglow LC similar to conical jet Effect of parameters on LC Early rebrightenings of GRB afterglow may be resulted from ring-shaped jets Conclusions 35 Thank you!