Dominic C. Marcello

A numerical method for generating rapidly rotating bipolytropic structures in equilibrium

We demonstrate that rapidly rotating bipolytropic (composite polytropic) stars and toroidal disks can be obtained using Hachisus self consistent field technique. The core and the envelope in such a structure can have different polytropic indices and also different average molecular weights. The models converge for high

A Very Fast and Angular Momentum Conserving Tree Code

T/|W|

WHAT IS THE SHELL AROUND R CORONAE BOREALIS

cases, where T is the kinetic energy and W is the gravitational energy of the system. The agreement between our numerical solutions with known analytical as well as previously calculated numerical results is excellent. We show that the uniform rotation lowers the maximum core mass fraction or the Sch

Accelerating Octo-Tiger: Stellar Mergers on Intel Knights Landing with HPX

\ddot{\rm{o}}

The Role of Dredge-up in Double White Dwarf Mergers

nberg-Chandrasekhar limit for a bipolytropic sequence. We also discuss the applications of this method to magnetic braking in low mass stars with convective envelopes.

Introducing Octo-tiger/HPX: Simulating Interacting Binaries with Adaptive Mesh Refinement and the Fast Multipole Method

There are many methods used to compute the classical gravitational field in astrophysical simulation codes. With the exception of the typically impractical method of direct computation, none ensure conservation of angular momentum to machine precision. Under uniform time-stepping, the Cartesian fast multipole method of Dehnen (also known as the very fast tree code) conserves linear momentum to machine precision. We show it is possible to modify this method in a way that conserves both angular and linear momenta.

Numerical simulations of mass transfer in binaries with bipolytropic components

The hydrogen-deficient, carbon-rich R Coronae Borealis (RCB) stars are known for being prolific producers of dust which causes their large iconic declines in brightness. Several RCB stars, including R CrB, itself, have large extended dust shells seen in the far-infrared. The origin of these shells is uncertain but they may give us clues to the evolution of the RCB stars. The shells could form in three possible ways. 1) they are fossil Planetary Nebula (PN) shells, which would exist if RCB stars are the result of a final, helium-shell flash, 2) they are material left over from a white-dwarf merger event which formed the RCB stars, or 3) they are material lost from the star during the RCB phase. Arecibo 21-cm observations establish an upper limit on the column density of H I in the R CrB shell implying a maximum shell mass of

A NUMERICAL METHOD FOR STUDYING SUPER-EDDINGTON MASS TRANSFER IN DOUBLE WHITE DWARF BINARIES

\lesssim

A Hybrid Advection Scheme for Conserving Angular Momentum on a Refined Cartesian Mesh

0.3 M

Evolving R Coronae Borealis Stars with MESA.

_{\odot}