Day 66

Tuesday.  Dad's BD dinner tonight, so will leave IPMU early today (4pm).  Will I talk to Mitra or Rachel this week?


1108.2270
Tidal disruption rate of stars by supermassive black holes obtained by direct N-body simulations
Brockamp, Baumgardt, Kroupa


* How often do stars be tidally disrupted by SMBH?


Assume inital stellar distribution around SMBH as Sersic n=4 profile (bulge).  1e3 to 5e5 particles around SMBH; three different BH capture radii to allow scaling or results for SMBH up to M~1e6 Msun.  Number of disrupted stars computed by diffusion in angular momentum space into the loss cone of BH; the rate scales with the total number of particles such that dN/dt ~ N^b, where b~0.83---steeper than the expected dN/dt ~ ln(N) derived from simple energy relaxation arguments.  Only a realtively modest dependence of the tidal disruption rate on the mass of SMBH is found.  The number of disrupted stars contribute a significant part of the mass growth of BH in the lower mass range if significant part of mass growth of BH is actually swallowed by the SMBH.  Direct consequence for the search and existence of IMBHs in globular clusters.  For SgrA* SMBHs, a tidal disruption rate of 55 +/- 27 events / Myr deduced.  Relaxation driven stellar feeding cannot account for the masses of massive BHs with M > 1e7 M_sun.


* Not sure if the assuptions that went into the calculation is correct (i.e., Sersic distribution of stars; diffusion mechanism).


1108.2009
Hangup Kicks: still larger recoils by partial spin/orbit alignment of BH binaries
Lousto, Zlochower


Gravitational radiation recoil studied in configurations of final remanent of BH binary merger that have components of the spin both aligned with the orbital angular momentum and in the orbital plane.  24 new simulations for equal-mass and equal-spin-magintude binaries (but with different spin orientations).  Include both new and known results.  Predicted new maximum velocity is 5000 km/s (rather big v/c), where this is reached for spins partially aligned with the orbital angular momentum.  Optimal configuration is near an equipartition of the hangup and superkick contributions.  Newly discovered contribution to the recoil---increase the probabilities of large reciols in generic astrophysical mergers.  Measure probabilities accretion-aligned spins and find non-negligible probabilities for SMBH encounters leading to recoil velocities of several thousand km/s.


* hangup?  superkick?
* c = 3e5 km/s, so 5e3 km/s => beta = 1.7e-2