Higher powered jets from black hole space-times

Transcription

1 Higher powered jets from black hole space-times L. Lehner (Uof Guelph/Perimeter Inst/CIFAR)

2 Gravitational Waves: Current detectors GEO600 TAMA/LCGT LIGO VIRGO AIGO/LIGO Aust? TAMA GEO VIRGO LIGO Hanford LIGO Livingston 2

3 (near?) Future detector: LISA. (main one for this talk)

4 Ideal source: Binary black holes [Pretorius 05,..]

5 (some) notable outcomes Radiation: convert ~ 5% of total intial mass and angular momentum. (can be higher for tuned collisions). E GW ~ ergs (M T /10 6 M sun ) in ~ 500 (M T /10 6 M sun ) secs L GW ~ L sun Asymmetric scenarios give rise to kicks, these can be as large as km/s! (claim Quasar SDSS J ) Yet these need some tweaking. A few 100s km/s more typical. (Mech Energy~ ergs (M T /10 6 M sun ) >> SN!) Additionally: System can profoundly influence neighboring matt/gas/plasma, etc.

6 LISA signals? LISA: superb signal to noise ratio. Excellent accuracy to: strain & freqn waves will be ``seen directly and to very large redshifts (z~ 5-15 ) h ~ [(1+z) M] 5/3 f 2/3 /d L ; f,t ~ [(1+z) M] 5/3 f 11/3 (arcmin 2 << deg 2 ) However: localization to ~ square degrees [Holtz-Hughes] distance obtained is redshift dependent (from Kocsis et.al. 2006,2008 and Holz-Hughes 05)

7 LISA signals? LISA: superb signal to noise ratio. Excellent accuracy to: strain & freqn waves will be ``seen directly and to very large redshifts (z~ 5-15 ) h ~ [(1+z) M] 5/3 f 2/3 /d L ; f,t ~ [(1+z) M] 5/3 f 11/3 However: localization to ~ square degrees [Holtz-Hughes] distance obtained is redshift dependent An electromagnetic counterpart resolves these issues Can get a purely gravitational & clean Hubble diagram! (d l vs z)

8 Nature cooperates Super massive binary black holes seem to exist NGC Black hole pair In the process of merging? Understand both gravitational and electromagnetic wave emissions from key systems Binary black holes interacting with surrounding media Ergs routinely inferred (~10 49 LHCs)?! The key is to tell observers what to look for

9 Studying relevant systems Deal with spacetime curvature Einstein equations. That s the solved part! (ie if you think about it.. NR can likely give the answer, for comparable masses that is.) Black holes are not really quite in vacuum must deal with fields describing gas and electromagnetic fields Poorly understood systems *we don t control the experiment+ Emission process? What physics? Electromagnetic fields? Matter, what matter?

10 Merger of galaxies -observations indicate the presence of supermassive BHs in the center of galaxies, surrounded by gas and an accretion disk - these galaxies have undergone mergers binary black hole merger - further, AGNs BHs are surrounded by a disc of matter likely magnetized.

11 Two fronts. (circumbinary picture) Pre/prompt/post - merger emissions? (pre/prompt) Binary black holes as stirrers of stuff (post) merged black hole as bully for matter

12 Binary black holes and emissions Different possible options. Postmerger events from circumbinary disks around BHs [Milosavljevic-Phinney; Lipai-Loeb; Lipai et.al, Bonning et.al; Bode et.al; O Neil et. al; Megevand et.al; Corrales et.al, etc.] Pre/merger events from gas/plasmas in between BHs / torques on disk [Armitage et.al; MacFadyen et.al.; Dotti et.al; Chang. et.al.; Palenzuela et.al.; Bode et.al ]

13 Binary black holes as blenders. A new spin on an old story How does the curvature/dynamics influence EM fields? Blandford-Znajek. Connected to Penrose process for Kerr bh s surrounded by magnetic fields (anchored by the disk) Stray charges accelerate photons pair production cascade. BH becomes surrounded by a tenuous conducting plasma with little inertia [Goldreich-Julian, Blandford-Znajek]

14 Approach: Force-free electrodynamics a T ab =0 a T ab (fluid) = - a T ab (em) = -F ab J a if ρ,p << B 2 then a T ab (fluid) << F ab J a 0 E J = 0, q E + J x B = 0 E B = 0 System can be studied in an ``effective way plasma supplies charges/currents which in turn enforce E.B = 0 furthermore, fields can carry charged particles, and establish a circuit

15 Basic picture from the membrane paradigm BH: (poor) conductor Battery: Black hole s rotation Plasma to close the circuit Far load: to dissipate energy L ~ B 2 a 2

16 Beyond the simple mp model F F F F A A A A so A A A A F F B E t r tr t r r t F r t r t ab ab,,,,,,,, Stationary spacetime: (Gammie,McKinney 04) horizon of out energy B and for r B F thus B B r B F T F with d g F E r H F F H H F r r r E r F Mr a F r E r t E E t H 0 0 ) ( )sin ( ) 2(, ) ( sin ) ( )sin ( ) 2( ) ( , Plasma is crucial for this to happen Also has its problems, lack of a known solution numerical calculations

17 Examples Kerr in vacuum and FF immersed in uniform field In vacuum no radiation With plasma currents on the horizon complete the circuit Membrane paradigm: wrt asymptotic observers, circuit moves through a B field EMF produced. BH becomes the battery. *Damour,Phinney,Thorne,McDonald +

18 load dependence

19 Single BHs, spin and alignment dependence [Palenzuela,Garret,LL.Liebling, PRD 2010] we knew. P ~ B 2 a 2 in the aligned case [Tchechovskoy,Narayan,McKinney 2010]. For misaligned case? Poynting flux still there, along B P ~ B 2 a 2 (1 + cos 2 ) (can be predicted using Damour 74 + mp!)

20 What if it moves? E.g. after black holes merge, individual black holes prior to merger. Where from? From membrane paradigm bh is a conductor. If moving through a B field, induce E ~ v x B EMF=V ~ (vb) ; L ~ V 2 /R Thus, L ~ B 2 v 2 (from boost) (Can be predicted using theory of satellite Propulsion Drell,Foley,Rudderman 65!)

21 Onto binary case At early times, dynamics deduced from membrane paradigm - + Radiation E ~ v B ; Flux ~ v 2 B 2

22 Onto the binary case Orbit Black holes move through B. Hall effect analogue! As in head-on case, circuit can be established due to charge separation Thus, expect Poynting flux through orbiting stages. Also at late time (BZ). [Palenzuela,LL,Liebling, Science 2010]

23 Poynting flux F

24 Putting all together: L ~ ( 1 [a/0.6] v 2 ) ergs [M 8 B 4 ] 2 For 10 4 G, 10 8 M O flux ~ ergs. IF Poynting flux energy efficiently transferred to observable emissions, interesting pre/post merger observations possible; to z=1?

25 After merger option Circumbinary disk knows a merger takes places after the fact ~ 5% energy radiated, most during last orbit: gravitational potential weakens suddenly Recoil in a given direction in both cases, the disk needs to readjust

26 final black hole retaliates Both mass reduction and recoil speed have an impact on the disk. If shocks develop shock energy onto the disk can induce EM signals from there on take your pick Lipai et. al. : prompt and in the UV Bonning et. al. : delayed and in soft Xrays Phinney et. al. : not kicks but mass reduction, significant output O Neil et. al. : not kicks but mass reduction, lowering of luminosity Corrales et. al.: kicks and mass reduction, 2D, energy sink considered

27 Symmetry preserving cases Internal energy reduction (same with pressure, temperature). Possible reduction in disk luminosity initially, but oscillates. Time variability governed by the disk s period

28 Symmetry breaking cases

29 Taking images.. Radiation transfer eqn: d I p d a u a( 0 0I Options: Brehmstralung-blackbody model brehmstralung emmisivity/blackbody (thin/thick) modified Krammer s opacity law ) Thermal model Kirchoff s law (Planck law) Krammer s opacity law Brehmstralung vanilla 2 T dv

30 Infrared Xrays

31 Summary LISA could jump start gravitational wave astronomy/cosmology by identifying electromagnetic counterparts to host galaxy where merger takes place Possibly new fundamental tests of gravity on cosmological scales can become available Still much to be understood, the field is just beginning to consider options and possibilities