Black HoleAstrophysics: Black Hole Astrophysics Chris Reynolds Department of Astronomy & Center for Theory & Computation, University of Maryland Beyond Einstein Meeting SLAC; 14th May 2004


Why care about black holes?: Why care about black holes? Astrophysics BHs responsible for most extreme astrophysical sources in current-day universe Might be central component of structure formation story Physics Strong-field GR has yet to be tested! BHs provide prime opportunity to perform tests New physics close to the event horizon?


Accreting Black Holes: Extreme Astrophysics: Accreting Black Holes: Extreme Astrophysics


Slide4: Core of the Perseus cluster (Chandra) Fabian et al. (2003)


Why care about black holes?: Why care about black holes? Astrophysics BHs responsible for most extreme astrophysical sources in current-day universe Might be central component of structure formation story Physics Strong-field GR has yet to be tested! BHs provide prime opportunity to perform tests New physics close to the event horizon Black Hole electrodynamics


Outline: Outline A brief primer on black hole accretion Why use X-rays? We’re already probing upto the event horizon! Spectral studies – emission lines from inner disk Timing studies – oscillation modes of inner disk Accreting black holes and Beyond Einstein


I : A primer on accretion: I : A primer on accretion Accretion disk The “engine” that converts Egrav  Erad + Ekin Accretion (angular mtm transport) driven by MHD turbulence Can support B-fields that thread the black hole (stretched) horizon Efficiency (L= dM/dt) Often high (=10-30%) Low ( <<1%) in certain situations (low or high accretion rate) ? Lynden-Bell (1969) Shakura & Sunyaev (1973) Novikov & Thorne (1974) Pringle (1981) Rees (1982) Balbus & Hawley (1991) Narayan & Yi (1994)


II : Why use X-rays?: II : Why use X-rays? MCG-6-30-15 HST/WFPC-2 XMM-Newton 0.5-10keV light curve (Fabian et al. 2002) Rapid X-ray variability of AGN strongly suggests X-rays come from innermost regions of accretion disk


Slide10: Relativistically broad and skewed emission lines from inner disk (High-frequency) quasi-periodic oscillations in accreting stellar mass black hole systems


III : Spectral studies and broad X-ray emission lines: III : Spectral studies and broad X-ray emission lines Iron line profile in MCG-6-30-15 (Tanaka et al. 1995)


Slide12: X-ray “reflection” imprints well-defined features in the spectrum Reynolds (1996)


Slide13: Parmar et al. (1984) Solar Maximum Mission (Bent Crystal Spectrometer) Iron fluorescence is a simple, well-understood, well-studied physical process! Iron K fluorescence from the Sun


Slide14: We observe very broad lines naïve interpretation gives velocities of 100,000 km/s Well fit by disk models Needs emission from very close to black hole (R~RSch) Fe fluorescence ~6-7keV band and (possibly) O/N/C recombination emission (<1keV) Can start doing strong-field gravitational astrophysics using these tools MCG-6-30-15 from XMM-Newton Continuum subtracted Fabian et al. (2002)


Are these features robust?: Are these features robust? Calibration problems? NO! Many well studied X-ray sources do not show such features. Problems with continuum subtraction? Maybe broad line is just a curved continuum? Maybe continuum suffers complex absorption? What about broadening mechanisms? All of these effects are calculable and can be folded into the models we use to examine the data


Slide16: MCG-6-30-15 (HST) XMM-Newton


Slide17: A portion of the June-2001 dataset for MCG-6-30-15


Slide22: Maybe additional absorption from iron K absorption lines could make this work… fine tuning needed? Astro-E2 will assess this model.


A taster of the current field…: A taster of the current field… See broadened emission lines in many (~25%) sources Find very broad lines in MCG-6-30-15 and GX339-4 Assuming validity of GR, the need for rapidly-rotating black holes is unambiguous Very centrally concentrated pattern of X-ray illumination needed to produce such lines Strong light bending effects? (Fabian, Minutti, Vaughan et al.) Magnetic torquing of inner accretion disk by spinning black hole? (Wilms, Reynolds et al. 2001; Li 2001; Reynolds et al. 2004) Either way, we’re debating processes occurring within the inner 2-3GM/c2


Slide24: GX339-4 MCG-6-30-15


A taster of the current field…: A taster of the current field… See broadened emission lines in many (~25%) sources Find very broad lines in MCG-6-30-15 and GX339-4 Assuming validity of GR, the need for rapidly-rotating black holes is unambiguous Very centrally concentrated pattern of X-ray illumination needed to produce such lines Strong light bending effects? (Fabian, Minutti, Vaughan et al.) Magnetic torquing of inner accretion disk by spinning black hole? (Wilms, CSR et al. 2001; CSR et al. 2004) Either way, we’re debating processes occurring within the inner 2-3GM/c2


Slide27: Accretion Luminosity Dissipation of work done by torque at radius of marginal stability


Slide28: MCG-6-30-15 Fit with a Novikov-Thorne/Page-Thorne disk CSR et al (2004)


Slide29: Fit with a Agol & Krolik torqued disk (need “infinite efficiency case) CSR et al (2004)


Alternatively…: Alternatively…


Slide31: G.Minutti & A.C.Fabian


IV : High-frequency QPOs: IV : High-frequency QPOs HFQPOs displayed by many accreting stellar-mass black holes Moderate quality factors (Q~few-10) Highest frequency QPOs > orbital frequency of non-rotating BH Often come in pairs with approximate 3:2 ratio Quantitative probe of strong gravity regime… Probably seeing the tip of a whole series of spectrum of QPOs But need a model to get anywhere… From review by McClintock & Remillard (2003)


“Diskoseismology”: “Diskoseismology” Attempts to understand HFQPOs in terms of normal modes of the accretion disk fluid Resonant cavity formed by relativistic potential g-, p-, and c-modes Theoretically attractive No natural explanation lin linear theory for the 3:2 ratio e.g. Nowak & Wagoner (1991, 1992) Perez et al. (1997) Silbergleit et al. (2001) Wagoner et al. (2001)


Slide34: Wagoner et al. (2001)


“Parametric resonance”: “Parametric resonance” Motivated by the 3:2 ratio of HFQPO frequencies Parametric resonance between radial & vertical epicyclic frequencies Expect 3:2 to be strongest resonance Precise nature of coupling or driving is not specified Two sets of 3:2 HFQPOs in GRS1915+105… can’t both be this parametric resonance? Kluniak & Abramowicz (2001) Abramowicz, Kluniak et al. (2004)


Slide36: M82-ULX source (Strohmayer et al. 2003) Evidence for an “intermediate-mass” scale BH?


Slide37: MHD accretion disk simulation (Hawley & Krolik 2001)


V : Black Hole Astrophysics & NASA’s Beyond Einstein: V : Black Hole Astrophysics & NASA’s Beyond Einstein Future X-ray component of BE is a crucial complement to gravitational wave studies BHFP (EXIST/CASTOR), Con-X and BHI (MAXIM) Growth of black holes in the universe Occurs primarily through efficient accretion (Soltan) Behavior of matter close to black hole Plasma/particle physics of accretion flows BH electrodynamics (Blandford-Znajek/Penrose mechanisms) Strong gravity Quantitative tests of strong-gravity (Kerr metric) using well known types of sources Easy to see deviations from GR (comparatively trivial template fitting)


High throughput spectroscopyConstellation-X: High throughput spectroscopy Constellation-X Proposed launch NET2016 Soft X-ray Telescope Microcalorimeter ~5-10 arcsec FWHM 0.25-10 keV band Large effective area and excellent spectral resolution Gratings V. high soft X-ray resolution Also, focusing hard X-ray telescope (up to 40-60keV) The Constellation-X Observatory (NASA)


Slide40: Armitage & CSR (2003)


Iron line variability: Iron line variability Con-X (XEUS) will allow detailed study of line variability See effects of non-axisymmetric structure orbiting in disk Follow dynamics of individual “blobs” in disk Quantitative test of orbital dynamics in strong gravity regime Armitage & CSR (2003)


Non-axisymmetric structure may have been seen already…: Non-axisymmetric structure may have been seen already… Chandra-HETG data on NGC3516 (Turner et al. 2002) Simulation results for inclination of 20 degs (summed over 2 full orbits) A prime science target for Astro-E2


Relativistic iron line reverberation…: Relativistic iron line reverberation… Reverberation X-ray source displays dramatic flares Flare produces “X-ray echo” that sweeps across accretion disk Iron line profile will change as echo sweeps across disk Needs high throughput spectroscopy – but likely within reach of Con-X CSR et al. (1999) Young & CSR (2000)


Slide44: Sensitive probe of strong gravity Get inward and outward propagating X-ray echoes inward propagating echo is purely a relativistic effect Inward propagating echo gives red-bump on the iron line profile Precise properties of red-bump are probe the Kerr metric (and allow measurement of BH spin) Side note… we already know that situation is not simple; Current data suggest complex ionization changes associated with variability Need hard X-ray capability of Con-X to deconvolve effects of disk ionization in a realistic spectrum.


Slide45: Reynolds et al. (1999)


Slide46: Constellation-X simulations


The Black Hole ImagerMicro-arcsecond X-ray Imaging Mission (MAXIM) : The Black Hole Imager Micro-arcsecond X-ray Imaging Mission (MAXIM) HST (0.1 arcsec) MAXIM (0.05 -arcsec)


Slide48: ~20,000 km Current MAXIM concept Group and package Primary and Secondary Mirrors as “Periscope” Pairs “Easy” Formation Flying (microns) All s/c act like thin lenses- Higher Robustness Possibility to introduce phase control within one space craft- an x-ray delay line- More Flexibility Offers more optimal UV-Plane coverage- Less dependence on Detector Energy Resolution Each Module, self contained- Lower Risk. ~500-1000 m Baseline See talk by W.Cash this afternoon.


Slide50: GR-MHD simulations by Hirose, Hawley & Krolik (2003)


Conclusions: Conclusions Have been dramatic observational and theoretical advances in our understanding of accreting black holes over past decade Spectral and timing X-ray observations are already probing region in immediate vicinity of accreting stellar & supermassive black holes X-ray astronomy is on the verge of realizing its ultimate promise (BHFP, Con-X, and BHI/MAXIM) Probe of BH growth back to cosmic “dark ages” Constraints on strong field gravity Detailed understanding of BH accretion Accessed through high-throughput spectroscopy (Con-X), and direct imaging (BHI)