The impact of stellar evolution on rotating star clusters: the gravothermal-gravogyro catastrophe and the formation of a bar of black holes. (arXiv:2205.04470v1 [astro-ph.GA])

The impact of stellar evolution on rotating star clusters: the gravothermal-gravogyro catastrophe and the formation of a bar of black holes. (arXiv:2205.04470v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kamlah_A/0/1/0/all/0/1">A. W. H. Kamlah</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Spurzem_R/0/1/0/all/0/1">R. Spurzem</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berczik_P/0/1/0/all/0/1">P. Berczik</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sedda_M/0/1/0/all/0/1">M. Arca Sedda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dotti_F/0/1/0/all/0/1">F. Flammini Dotti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Neumayer_N/0/1/0/all/0/1">N. Neumayer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pang_X/0/1/0/all/0/1">X. Pang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shu_Q/0/1/0/all/0/1">Q. Shu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tanikawa_A/0/1/0/all/0/1">A. Tanikawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Giersz_M/0/1/0/all/0/1">M. Giersz</a>

We present results from a suite of eight direct N-body simulations, performed
with textsc{Nbody6++GPU}, representing realistic models of rotating star
clusters with up to $1.1times 10^5$ stars. Our models feature primordial
(hard) binaries, a continuous mass spectrum, differential rotation, and tidal
mass loss induced by the overall gravitational field of the host galaxy. We
explore the impact of rotation and stellar evolution on the star cluster
dynamics. In all runs for rotating star clusters we detect a previously
predicted mechanism: an initial phase of violent relaxation followed by the
so-called gravogyro catastrophe. We find that the gravogyro catastrophe reaches
a finite amplitude, which depends in strength on the level of the bulk
rotation, and then levels off. After this phase the angular momentum is
transferred from high-mass to low-mass particles in the cluster (both stars and
compact objects). Simultaneously, the system becomes gravothermally unstable
and collapses, thus undergoing the so-called gravothermal-gravogyro
catastrophe. Comparing models with and without stellar evolution, we find an
interesting difference. When stellar evolution is not taken into account, the
whole process proceeds at a faster pace. The population of heavy objects tend
to form a triaxial structure that rotates in the cluster centre. When stellar
evolution is taken into account, we find that such a {it rotating bar} is
populated by stellar black holes and their progenitors. The triaxial structure
becomes axisymmetric over time, but we also find that the models without
stellar evolution suffer repeated gravogyro catastrophes as sufficient angular
momentum and mass are removed by the tidal field.

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