Date: Wednesday 13-Nov-2024
Time: 11:30-12:30 pm
Location: PSC 1136
Speaker: Lizhong Zhang (Flatiron Institute)
Title: Understanding the dynamics of accretion onto neutron stars and black holes in relativistic radiation MHD simulations
Abstract: Radiation-driven dynamics plays an essential role in understanding accretion physics around neutron stars and black holes, particularly in super-Eddington regimes. In super-Eddington accretion onto a black hole, thermal instability causes the disk to expand. This expansion is constrained by magnetic tension along the jet, which shapes a conical funnel in the outflow region. For accretion onto a strongly magnetized neutron star, the magnetic field disrupts the disk geometry, channeling accretion flows along field lines toward the magnetic poles. At sufficiently high accretion rates, radiation pressure supports this magnetically confined flow, forming a column structure at the poles. To quantify these dynamics, we solve (general) relativistic MHD equations coupled with angle-dependent radiation transfer, allowing us to capture the effects introduced by radiation and magnetic fields in extreme environments. The simulation results aligns with several recent observational findings and provides the diagnostics for future observations.
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