1 Astrophysical black holes Chris Reynolds Department of Astronomy

2 Topics Observational evidence for black holes X-ray studies of strong-gravity region First observational studies of BH spin Future directions

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5 Observational evidence for black holes Early X-ray observations [1965] discovered a powerful X-ray source in Cygnus Cygnus X-1 – Binary star system… black hole in orbit around a massive O-star – Black hole mass 7-13 M – X-rays produced due to accretion of stellar wind from O-star – 2kpc away

6 How do we know the black hole mass? Period 5.6 days K = V sin i = 75km/s Newtonian analysis… – M BH >f – Cyg X-1… f=0.24M BH Feed in knowledge of i and companion mass… M=7-13M sun 6 “golden” cases with f>3M sun Brocksopp et al. (1998)

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9 A. Ghez (UCLA) Strong evidence for a 3-4 million solar mass BH at the Galactic Center (closest stellar approach only 40AU!)

10 Chandra+VLA image of GC (Baganoff et al. 2001) X-ray studies of black holes

11 MCG (Seyfert gal) (L X ~10 36 W) 3C273 (Quasar) L X ~10 38 W

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13 X-ray “reflection” imprints well-defined features in the spectrum

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15 Relativistic effects imprint characteristic profile on the emission line… Iron line profile in MCG

16 MCG Suzaku (Miniutti et al. 2006)

17 Also see Suzaku results on broad iron lines at this meeting: MCG (Reeves et al.) NGC 3516 (Markowitz et al.) Systematic surveys of the XMM archive are showing that ~1/2 of type-1 AGN show broad iron lines (largely confirming ASCA results) MCG (Dewangan 2003) NGC2992 IRAS (Iwasawa 2004)

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19 Brenneman & Reynolds (2006) Assuming no emission from within r ms a>0.987 (formal 90% limit) XMM analysis of MCG

20 Black Hole Quasi-periodic oscillations High-frequency QPOs – Comparable frequency to orbital frequency in inner accretion flow – Often found in pairs with 3:2 ratio Stable frequencies – probably determined by gravitational potential – Could be an excellent probe of the mass and spin!!

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23 QPO theory Lack of standard QPO theoretical framework is problem Global modes of accretion disk – “Diskoseismology”; Wagoner, Nowak, Kato… – Produce g-, p-, and c-modes – Linear theory… no natural explanation for 3:2 ratio Resonance model – Parametric resonance between vertical/radial epicyclic frequencies (Abramowicz & Kluzniak) – Source of free energy? Fundamental g-mode (Nowak & Wagoner) Movie by Mike Nowak

24 The Future of BH X-ray Studies Armitage & Reynolds (2004) Dynamical timescale variability… probes orbital motions in accretion disk

25 Powerful probe of turbulent disk physics. Also, arcs approximately trace test-particle Keplerian orbits in  =  plane. Iwasawa et al. (2004)

26 Light crossing timescale allows reverberation effects to be studied.

27 Chandra Deep Field

28 Constellation-X simulations… Simulated 100ks; F 2-10 = erg/s/cm 2 Simulated 1Ms; z=1; F 2-10 = erg/s/cm 2 ~4 such source per Con-X field

29 Imaging a black hole mm-VLBI

30 Imaging a black hole Micro-arcsecond X-ray Imaging Mission (MAXIM) HST (0.1 arcsec) MAXIM (0.05  -arcsec)

31 ~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. ~ m Baseline A scalable MAXIM concept.