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

Outline  Tidal disruption event (TDE) and Swift J observation  X-ray flares of Swift J  Long-term X-ray emission  Quasi-periodic oscillation (QPO)  Summary FAN4 Workshop

Galactic centers: some are active, most are dormant M87; NASA/Hubble Ghez et al 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 FAN4 Workshop

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~ yr -1 gal -1 Rate of TDEs~ 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 FAN4 Workshop

Swift J : 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 FAN4 Workshop

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

Zauderder et al FAN4 Workshop

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

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) FAN4 Workshop

Internal-shock model for X-ray flares Reverse shock Forward shock Yu & Dai 2009 Two shocks structure: shocked material unshocked material L1 γ1 L4γ4L4γ FAN4 Workshop See Prof. Z. G. Dai’s talk

Wang & Cheng 2012 t=3 days t=31 hrs FAN4 Workshop

Wang & Cheng 2012 Zauderder et al 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! FAN4 Workshop

2. Long-term X-ray emission Saxton et al There are many pulses with long duration times ( 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 FAN4 Workshop

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

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 FAN4 Workshop

Light curve Zou, Wang & Cheng FAN4 Workshop 1<α<1.5

Photon index evolution Zou, Wang & Cheng FAN4 Workshop

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

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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 FAN4 Workshop

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 FAN4 Workshop21 Barthelmy et al. 2005, NatureBurrows et al Science GRB

Energy frequency distribution FAN4 Workshop22 83= 9 (short)+74 (long) Wang & Dai 2013, Nature Phys

Duration time distribution FAN4 Workshop23 Wang & Dai 2013, Nature Phys

Waiting time distribution FAN4 Workshop24 Wang & Dai 2013, Nature Phys

Magnetic reconnection? FAN4 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.

Self-organized criticality (SOC)? FAN4 Workshop26

Summary Swift J is the first TDE with jet and QPO The internal shock model can explain the X-ray flares of Swift J 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 FAN4 Workshop Thanks for your attention!