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SUMMARY:Collisionless losscone refilling: the end of the final parsec prob
 lem - Alessia Gualandris (Surrey)
DTSTART:20191010T150000Z
DTEND:20191010T160000Z
UID:TALK131428@talks.cam.ac.uk
CONTACT:28811
DESCRIPTION:Mergers of massive black hole binaries (BHBs) are expected to 
 be a key\nsource of\ngravitational waves (GWs). However\, the expected num
 ber and frequency\nof such mergers remains highly uncertain. This owes to 
 a\nlong-standing puzzle known as the final parsec problem. Gravitational\n
 N-body simulations that assume a spherical distribution of stars\nsurround
 ing the BHB find that the binary stalls when all stars on\nintersecting or
 bits have been ejected. This is inconsistent with\navailable observations:
  every massive galaxy observed to date appears\nto host a single supermass
 ive black hole\, and only a handful of BHB\ncandidates exist.  \nI will r
 eview the final parsec problem and present a new approach to\ndetermine wh
 ether collisionless repopulation of the binary's losscone in\nnon-spherica
 l nuclei is a viable mechanism to drive binary coalescence.\nI will presen
 t results of direct summation N-body simulations of\ngalaxy mergers\, runn
 ing on multiple GPUs. These allow to measure the binary\nhardening rate an
 d determine a new proxy that depends only on the stars'\nangular\nmomentum
 .\nI will then present collisionless simulations of spherical and\nnon-sph
 erical isolated models to increase the number of particles\nsufficiently t
 hat collisional effects become unimportant and\ncollisionless losscone ref
 illing can be measured.\n
LOCATION:Sackler Lecture Theatre\, IoA (tea at 3:30 pm)
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