Mitch Begelman JILA, University of Colorado ACCRETING BLACK HOLES and their jets

WHY ACCRETING BLACK HOLES ARE INTERESTING Most efficient means of energy liberation in nearby universe Strong GR effects Behavior of extremely relativistic plasmas Liberated energy strongly affects galaxy evolution

3 FOCUS AREAS Accretion physics Jet physics Demographics (formation + feedback)

ACCRETION PHYSICS

4 FACTORS INFLUENCE ACCRETION Angular momentum –almost always too large to fall straight in –liberated energy transferred outward by torque Radiative efficiency –energy accumulates unless large fraction is radiated –low efficiency  pressure forces dominate accretion flow Magnetic flux –Poloidal flux conserved: hard to accumulate –Catalyzes angular momentum transport –Global dynamics: magnetically arrested + supported disks –Drives jets Black hole spin –all spin energy extractable by magnetic fields –up to 29% of gravitating mass perceived at 

BLACK HOLE ACCRETION l > GM/c l < GM/c Radial (Bondi) Centrifugally choked NOYES Radiatively efficient? ( Ṁ / Ṁ E ) RIAFThin Disk Nearly Keplerian? Rotation important? YESNO SLIM DISK ADAF ADIOS STARLIKE w/ narrow funnel BH spin, Mag. flux? Jets YES

ACCRETION PHYSICS Super-Eddington (hyper-) accretion … when disks look like stars

SS433: A CLASSIC CASE OF HYPERACCRETION Strong wind from large R

l/l Kep disk opening angle Gyrentropes: s ( l ) Quasi-Keplerian Inflates to axis when l ~ l Kep

Radiatively inefficient Too much ang. mom. to fall straight in, not enough to form a disk  Density/pressure profiles steepen  runaway accretion (>> L Edd ), must produce jets or blow up DISKLIKE  STARLIKE ACCRETION

EXAMPLES of STARLIKE ACCRETION (some) Tidal Disruption Events –fallback of debris from tidally disrupted star –evolution from super-Eddington  sub-Eddington Gamma-Ray Bursts –mass supply from collapse of stellar envelope –enormously super-Eddington (> ) –fastest known jets (  ~ ) SMBH seeds –hyper-accretion from inflated envelope (quasi-star)

Super-Eddington TDE Swift J Tchekhovskoy et al Swift + Chandra light curves L corrected for beaming Radio “re-brightening” after ~ 4 months

ACCRETION PHYSICS Super-Eddington (hyper-) accretion … when disks look like stars Highly magnetized disks

A lot of thin disk theory doesn’t “fit”… Thermal/viscous instability not seen Evidence for ultra-compact coronae No explanation for hysteresis of XRB state transitions Disks thicker and hotter than predicted Inflow speeds faster than predicted Quasars exist (!) despite predictions of disk self-gravity HIGH DISK MAGNETIZATION A POSSIBLE SOLUTION!

Spectral “states” Follows a specific sequence Two-dimensional cycle = “hysteresis” Fender, Belloni & Gallo 2004 LOW- HARD HIGH- SOFT INTERMED. QUIESCENT X-ray Binary Evolution

MAGNETIC DISK PHENOMENA Poloidal flux accumulation –advection from environment –buildup through stochastic fluctuations Viscous parameter  correlated with poloidal field –the “second parameter” needed for hysteresis? Magnetically arrested disk (MAD) –Coupling to BH spin, jets Accretion disk dynamo HIGH  LOW 

ACCRETION DISK DYNAMO Salvesen et al. 2015

ACCRETION DISK DYNAMO Salvesen et al. 2015

ACCRETION DISK DYNAMO Salvesen et al. 2015

JET PHYSICS

Magnetic vs. radiative propulsion

Are jets always propelled by coherent magnetic fields? Magnetic flux threading engine Angular velocity of engine Jet power limited by amount of flux available

Transient accretion events have access to a fixed amount of flux… Tidal Disruption Event candidate Swift J : Jet power: L j > erg s -1 ~ 100 L E Flux needed:  > G-cm 2 Flux available:   ~ B 3 (R  /R  ) 2 G-cm 2 Collapsar Gamma-Ray Burst: Jet power: L j > erg s -1 ~ L E Flux needed:  > G-cm 2 Flux available:   ~ B 3 (R  /R  ) 2 G-cm 2

JET MAGNETIC PARADIGM REVISITED PRO –magnetocentrifugal mechanism –BZ coupling to BH spin –blazar jets: not enough radiation pressure –electron cooling can quench gas pressure –radiation drag limits  CON –insufficient magnetic flux! –magnetic propulsion inefficient at  >> 1 –GRBs, TDEs, quasi-stars: plenty of radiation –gas pressure OK if ions decoupled from electrons –radiation drag easy to shield against

g eff MRI Buoyant loops of B form inward corona

g eff MRI … so jet ultimately powered by dissipation of turbulent B

g eff Reconnection MRI Reconnection converts energy to radiation

g eff Reconnection MRI Entrainment (by rad’n force) Mass-loading, collimation and acceleration

g eff Reconnection MRI Entrainment (by rad’n force) Self-shielding (from drag) Self-shielding from radiation drag

Radiation driven jets, opaque  fastest ⁻Lorentz factor ~ (L/L E ) small power (~1/4??) ⁻GRBs: L/L E ~   ~ 100 – 1000 Magnetically driven jets, tenuous  slower ⁻  ~ few  10s (e.g., blazars) ⁻Poynting flux persists to large r

JET PHYSICS Magnetic vs. radiative propulsion Dissipation: shocks vs. reconnection

Shocks ⁻“Cold,” weakly magnetized jets ⁻quenched when Poynting flux ~ K.E. ⁻“diffusive” particle acceleration Reconnection ⁻Favored in highly magnetized regions ⁻Poynting flux persists to large r ⁻nonlinear particle acceleration WHY DO JETS SHINE? BOTH PRODUCE NONTHERMAL SPECTRA

Mechanisms of Jet Dissipation Particle-dominated Poyntin Current-driven instabilities + reconnection Internal shocks + Fermi acceleration Shear instab. (KH, CD) + reconnection Poynting- dominated

Gamma-Ray Flares in the Crab (AGILE, FERMI) Apr 2011 Buehler+ ~1/yr for  t ~ 1 day h > 300 MeV extremely hard E iso ~ 4 x erg EVIDENCE OF RECONNECTION

SYNCHROTRON INVERSE COMPTON (Buehler+2012) >100 MeV! Apr Synchrotron emission h > 160 MeV  E > B, not shock acceleration 375 MeV!

Gamma-ray (TeV) flares in blazars Few minutes  compact region of high energy density and/or strong beaming Hard flaring spectrum Internal pair opacity   bulk ~ (BL Lacs) External pair opacity  r ~ pc scales (FSRQs) Infer: Localized, extremely beamed radiation far from jet source (jets-in-a-jet). Natural consequence of reconnection in highly magnetized jet.

RECONNECTION RENAISSANCE All reconnection is fast!

Time evolution of reconnection Current sheet breaks up into small-scale plasmoids

RECONNECTION RENAISSANCE All reconnection is fast! Robust predictions of particle acceleration

Werner et al. 14 Extremely flat spectra:  syn  0 for 

RECONNECTION RENAISSANCE All reconnection is fast! Robust predictions of particle acceleration “Kinetic Beaming” and rapid variability –beaming & bunching a function of particle energy –E iso depends on photon energy

Solid angle containing 50% flux: Energy-dependent synchrotron anisotropy Aitoff projection t = 397 ω c -1 Ω 50% /4π = 0.35 Ω 50% /4π = 0.18 Ω 50% /4π = 0.04 (Cerutti+ 2013)

High-energy variability from particle bunching and anisotropy Beam of high-energy particles sweeps across the line of sight intermittently  bright symmetric flares Density of γ >10 particles

RECONNECTION RENAISSANCE All reconnection is fast! Robust predictions of particle acceleration “Kinetic Beaming” –beaming & bunching a function of particle energy –E iso depends on photon energy “Extreme Acceleration” –electrons trapped in current sheet E>B –ε syn > 160 MeV (radiation reaction limit)

B. Cerutti & G. Werner

These issues and more feed into demographic campaigns… What do hyperaccreting BHs look like? How should we interpret the spectra/vaiability of jet? Spin bias

Compilation of spin constraints 1/4/2016Extremes of BH Accretion47 Reynolds (2014) Vasudevan et al. (2015)

Spin Bias 1/4/2016Extremes of BH Accretion48 Higher spin  higher efficiency  more luminous Expect high spin sources to be over-represented Vasudevan et al. (2015) … also Brenneman et al. (2011) n(a)~const n(a)~a n(a)~a 2

3x2 for the 2020s Demographics –find the rapidly accreting “seed” SMBHs –relate GRBs/SNe to BH masses and spins Accretion physics –discover the origin of QPOs and state transitions –understand whether and when the Eddington limit is a limit Jet physics –determine whether jets are powered by BH spin and how they are mass-loaded –discover how jets shine and what their radiation tells us about their power and composition

A KILLER APP? FINDING BLACK HOLES IN THEIR YOUTH