1. Close encounters between stars and Massive Black Holes Clovis Hopman Weizmann Institute of Science Israel Advisor: Tal Alexander

2. Tidally powered stars in the Galactic Center Tidally powered stars in the Galactic Center Ultraluminous X-ray sources Ultraluminous X-ray sources Gravitational Wave Radiation Gravitational Wave Radiation Dissipative stellar processes near Massive Black Holes

3. The stellar cusp near a BH

4. Tides and Gravity Waves Tides GWR

5. How to get near a Massive BH

6. Race between inspiral and scattering Alexander & Hopman, ApJL 2003

7. Kozai mechanism near MBHs Deviations from spherical symmetry in GC? Kozai eccentricity oscillations drive stars effectively towards the MBH (Hopman, Subr & Alexander 2005, in prep.)

8. Squeezars: Tidal Power

9. Squeezars in Galactic Centers are transient sources Surviving tidal heating Survival: low mass MBHs and efficient cooling

10. Squeezars Stars powered by tidal “squeezing” Stars powered by tidal “squeezing” Squeezars observable in Galactic Center (Alexander & Morris, ApJL 2003) Squeezars observable in Galactic Center (Alexander & Morris, ApJL 2003) ~ 1 squeezar in GC (Alexander & Hopman, ApJL 2003) ~ 1 squeezar in GC (Alexander & Hopman, ApJL 2003) Kozai: many more squeezars? (Hopman, Subr & Alexander 2005, in prep.) Kozai: many more squeezars? (Hopman, Subr & Alexander 2005, in prep.) Squeezars evaporate near MBHs Squeezars evaporate near MBHs

11. Ultraluminous X-ray Sources Super Eddington luminosities Super Eddington luminosities IBH: engine of ULX? IBH: engine of ULX? IBH can be formed dynamically in cluster (Portegies Zwart et al., Nature 2004) IBH can be formed dynamically in cluster (Portegies Zwart et al., Nature 2004)

12. What feeds the IBH?? Clusters contain too little gas Clusters contain too little gas Tidal disruption of star gives only short (~yr) flare (Rees, Nature 1988) Tidal disruption of star gives only short (~yr) flare (Rees, Nature 1988) Solution: Tidal Capture!

13. ULX: IBH fed by a tidally captured star Circularization possible around IBH Circularization possible around IBH Roche lobe overflow supplies gas Roche lobe overflow supplies gas ULX can switch on after cluster evaporates ULX can switch on after cluster evaporates Lifetime and luminosity as observed Lifetime and luminosity as observed

14. Circularization Hopman, Portegies Zwart & Alexander, ApJL 2004 N-body simulations show tidal capture (Baumgardt, Hopman & Portegies Zwart 2005, in prep.)

15. Captured Stars Rate independent of relaxation time Hopman, Portegies Zwart & Alexander, ApJL 2004 Probability = Capture Rate Stellar Lifetime 10 %

16. Hopman, Portegies Zwart & Alexander, ApJL 2004 Mass Transfer and Luminosity

17. Gravitational Wave Radiation

19. Monte Carlo tracks in phase space Hopman & Alexander, astro-ph/0503672. Length scale a c delimits volume of inspiral stars Stars perform random walk in phase space

20. Barack & Cutler, PRD 2004 Eccentricity of LISA stars

21. LISA Stars in the Strong Gravity Regime Hopman & Alexander, astro-ph/0503672. Massive Black Holes:Intermediate Mass Black Holes:

22. Mass segregation: Heavy stars closer to MBH! Mass segregation: Heavy stars closer to MBH! Rate independent of relaxation time Rate independent of relaxation time Orbits are very eccentric Orbits are very eccentric Probably no signal from IBHs Probably no signal from IBHs Hopman & Alexander, astro-ph/0503672.

23. Conclusions Squeezars observable in Galactic Center Squeezars observable in Galactic Center Tidally captured stars around IBHs may be the engine that powers ULXs Tidally captured stars around IBHs may be the engine that powers ULXs LISA stars will be highly eccentric LISA stars will be highly eccentric