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SUMMARY:The Dynamics of Debris Disk Creation in Neutron Star Mergers - Yos
 sef Zenati (Open University)
DTSTART:20250613T103000Z
DTEND:20250613T113000Z
UID:TALK232699@talks.cam.ac.uk
CONTACT:Sandro Tacchella
DESCRIPTION:The detection of GW170817/AT2017gfo inaugurated an era of mult
 imessenger astrophysics\, in which gravitational-wave and multiwavelength 
 photon observations complement one another to provide unique insight into 
 astrophysical systems. A broad theoretical consensus exists\, in which the
  photon phenomenology of neutron star mergers largely rests upon the evolu
 tion of the small amount of matter left on bound orbits around the black h
 ole or massive neutron star remaining after the merger. Because this accre
 tion disk is far from inflow equilibrium\, its subsequent evolution depend
 s very strongly on its initial state\, yet very little is known about how 
 this state is determined. Using both snapshot and tracer particle data fro
 m a numerical relativity/MHD simulation of an equal-mass neutron star merg
 er that collapses to a black hole\, we show how gravitational forces arisi
 ng in a nonaxisymmetric\, dynamical spacetime supplement hydrodynamical ef
 fects in shaping the initial structure of the bound debris disk. The work 
 done by hydrodynamical forces is ∼10 times greater than that due to time
 -dependent gravity. Although gravitational torques prior to remnant relaxa
 tion are an order of magnitude larger than hydrodynamical torques\, their 
 intrinsic sign symmetry leads to strong cancellation\; as a result\, hydro
 dynamical and gravitational torques have a comparable effect. We also show
  that the debris disk's initial specific angular momentum distribution is 
 sharply peaked at roughly the specific angular momentum of the merged neut
 ron star's outer layers\, a few r g c\, and identify the regulating mechan
 ism.
LOCATION:Ryle Seminar Room\, KICC + online
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