Hydrodynamical Simulations

Simulating TŻO Formation

A TŻO can be created when a newly formed neutron star (NS) gets “kicked” into its companion star, which we call the “impact scenario”.

Using a moving mesh solver (MANGA) on top of the smooth particle hydrodynamics (SPH) code, Charm N-body GrAvity solver (ChaNGa), we simulated 5 main sequences (MS) masses spanning 5 - 15 solar masses, with three different periastron distances ($r_p$).

This is a simulation showing the NS (denoted by the x marker) colliding with a 7 solar mass main sequence star (the pentagon represents the core of the MS star). The TŻO fully merges at around 3 days and settles into hydrostatic equilibrium.

Radial Profiles

Separation between the center of the MS star and the NS over simulation time is plotted in the left column, with central density of our dTŻOs plotted in the right column. Each line is colored by the progenitor mass, ranging from 5 to 15 solar masses. Each row corresponds to a different $r_p$, with $r_p = 0$ representing a direct collision, $r_p = 0.5$ representing an envelope disturbance, and $r_p = 1$ being a grazing encounter. (Williams et al. 2025)