1. Modeling the X-ray emission and QPO of Swift J1644+57 Fayin Wang ( 王发印） Nanjing University, China Collaborators: K. S. Cheng (HKU), Z. G. Dai (NJU), Y. C. Zou (HUST)

2. Outline  Tidal disruption event (TDE) and Swift J1644+57 observation  X-ray flares of Swift J164+57  Long-term X-ray emission  Quasi-periodic oscillation (QPO)  Summary 2015-5-232FAN4 Workshop

3. Galactic centers: some are active, most are dormant M87; NASA/Hubble Ghez et al. 2005 Sgr A* NGC 3115 Canada-France-Hawaii Telescope Tidal disruption event (TDE) can light dormant SMBH. So TDE is promising tool to probe galactic center BHs. 2015-5-233FAN4 Workshop

4. Unlucky Star tidal disrupted by SMBHs RtRt When a star’s orbit in tidal radius (tidal force=self gravity) it is tidally disrupted. For a solar type star Rate of TDEs~10 -5 -10 -3 yr -1 gal -1 Rate of TDEs~10 -5 -10 -3 yr -1 gal -1 (e.g. Wang& Merritt 2004) (Rees 88; Evans & Kochanek 89; Li et al. 02; Strubbe & Quataert 09; Lodato et al.09; …) Fallback time (most bound material): t f ~ days to weeks. Rees 88 R t ~10 13 (M BH,6 ) 1/3 cm 2015-5-234FAN4 Workshop

5. Swift J1644+57: first TDE with a jet  /X-ray IR-Optical Radio Triggered Swift BAT on March 28, 2011 Triggered BAT 3 more times over next few days Remains bright in X-rays IR and Radio Brightening Host galaxy at z = 0.35 (Levan et al. 2011; Bloom et al. 2011; Burrows et al. 2011; Zauderder et al. 2011) NOT a (normal) GRB - low luminosity - duration ~ months NOT a normal AGN - no evidence for AGN or past activity Levan et al. 2011, Science 2015-5-235FAN4 Workshop

6. Host Galaxy at z = 0.35 Not an AGN Within < 150 pc of galactic center  SMBH origin L X > 10 48 erg s -1 > 10000 L Edd of 10 6 M ⊙ black hole  super-Edd accretion and/or beaming Levan et al. 2011 2015-5-236FAN4 Workshop

7. Zauderder et al. 2011 2015-5-237FAN4 Workshop

8. Blazar model for Swift J1644+57 synchrotron self-absorption  R radio > 10 16 cm  Г~20  external shock from ISM interaction (Giannios & Metzger 2011) X-ray variability  R X ~ c  t X  2 ~ 3 x 10 14 (  /20) 2 cm  “internal” process (e.g. shocks, reconnection) t ~ 3 days X-rays radio Bloom et al. 2011 Fermi LAT Av=3-5 Emission from the accretion disk is Compton-upscattered, giving rise to the observed x-rays. 2015-5-238FAN4 Workshop

9. 1.Internal model for X-ray flares Levan et al. 2011, Science Many flares in the X-ray band! X-ray flux increases 10 times in 200 seconds, from internal shocks. For Lorentz factor about 20, the critical frequencies of external shock (radio and optical) 2015-5-239FAN4 Workshop

10. Internal-shock model for X-ray flares Reverse shock Forward shock Yu & Dai 2009 Two shocks structure: shocked material unshocked material 1 2 34 L1 γ1 L4γ4L4γ4 2015-5-2310FAN4 Workshop See Prof. Z. G. Dai’s talk

11. Wang & Cheng 2012 t=3 days t=31 hrs 2015-5-2311FAN4 Workshop

12. Wang & Cheng 2012 Zauderder et al. 2013 Internal shock external shock Chandra observation at 630 days Our model also predicts that the external shock will dominate the X-ray emission when the internal shock has ended. Our prediction is confirmed by observation! 2015-5-2312FAN4 Workshop

13. 2. Long-term X-ray emission Saxton et al. 2012 There are many pulses with long duration times (10 5 -10 6 s) are found at later observation in the X-ray band. jet precession? Possibly warped disk around rapidly spinning BH (Lei et al.2012; Bardeen- Petterson effect due to stellar orbit not being in BH equatorial plane, leads to jet precession) Lei et al.2012 2015-5-2313FAN4 Workshop

14. 14 BH How to produce late X-ray pulses? External Shock Internal Shocks X-ray flares ISM Combined shellX-ray pulse 2015-5-23FAN4 Workshop

15. The Lorentz factor of the external shock is The critical frequencies of the synchrotron emission are (for energy injection) The peak observed flux density is Zou, Wang & Cheng 2013 2015-5-2315FAN4 Workshop

16. Light curve Zou, Wang & Cheng 2013 2015-5-2316FAN4 Workshop 1<α<1.5

17. Photon index evolution Zou, Wang & Cheng 2013 2015-5-2317FAN4 Workshop

18. 3. Quasi-periodic oscillation(QPO) Reis et al. 2012, Science 3.8σ 2.2σ Q=15 QPO at ν=4.8 mHz 2015-5-2318FAN4 Workshop

19. 2015-5-2319FAN4 Workshop

20. So the power spectrum The clumpy accretion scale is a steady outflow plus a clumpy shells with a periodic modulation at a frequency ω 0 β is the fraction of discrete shells in the total outflow gas. τ gives the width of the QPO frequency, A is the amplitude. From the properties of QPO observed by Suzaku and XMM-Newton, We find β=0.3. Wang et al. 2013 2015-5-2320FAN4 Workshop

21. 4. Statistics of X-ray flares Nearly half of GRBs have X-ray flares, including long and short GRBs. But the physical origin is mysterious, many models have been proposed. 2015-5-23FAN4 Workshop21 Barthelmy et al. 2005, NatureBurrows et al. 2005 Science GRB 050724

22. Energy frequency distribution 2015-5-23FAN4 Workshop22 83= 9 (short)+74 (long) Wang & Dai 2013, Nature Phys

23. Duration time distribution 2015-5-23FAN4 Workshop23 Wang & Dai 2013, Nature Phys

24. Waiting time distribution 2015-5-23FAN4 Workshop24 Wang & Dai 2013, Nature Phys

25. Magnetic reconnection? 2015-5-23FAN4 Workshop25 Similar distributions between GRB X-ray flares and solar flares may reflect an underlying system in a state of self-organized criticality (Bak, Tang, & Wiesenfeld 1987) where many composite systems will self-organize to a critical state in which a small perturbation can trigger a chain reaction that affects any number of elements within the system.

26. Self-organized criticality (SOC)? 2015-5-23FAN4 Workshop26

27. Summary Swift J1644+57 is the first TDE with jet and QPO The internal shock model can explain the X-ray flares of Swift J1644+57 The energy injection can explain the long term X-ray emission The clumpy component comprises about 30% of outflow Strong relativistic jet results in unique properties of this event! SOC property of GRB X-ray flares 2015-5-2327FAN4 Workshop Thanks for your attention!