A Comparison of Grid-based and SPH Binary Mass-transfer and Merger Simulations
- Indiana University Kokomo, School of Sciences, P.O. Box 9003, Kokomo, IN 46903-9004 (United States)
- Louisiana State University, Department of Physics and Astronomy, 202 Nicholson Hall, Baton Rouge, LA 70803-4001 (United States)
- College of Science and Math, University of Virgin Islands, St. Thomas, United States Virgin Islands 00802 (United States)
- Center for Theoretical Astrophysics/CCS-2, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 (United States)
- TLT-Turbo GmbH, Gleiwitzstrasse 7, 66482 Zweibrücken (Germany)
There is currently a great amount of interest in the outcomes and astrophysical implications of mergers of double degenerate binaries. In a commonly adopted approximation, the components of such binaries are represented by polytropes with an index of n = 3/2. We present detailed comparisons of stellar mass-transfer and merger simulations of polytropic binaries that have been carried out using two very different numerical algorithms—a finite-volume “grid” code and a smoothed-particle hydrodynamics (SPH) code. We find that there is agreement in both the ultimate outcomes of the evolutions and the intermediate stages if the initial conditions for each code are chosen to match as closely as possible. We find that even with closely matching initial setups, the time it takes to reach a concordant evolution differs between the two codes because the initial depth of contact cannot be matched exactly. There is a general tendency for SPH to yield higher mass transfer rates and faster evolution to the final outcome. We also present comparisons of simulations calculated from two different energy equations: in one series, we assume a polytropic equation of state and in the other series an ideal gas equation of state. In the latter series of simulations, an atmosphere forms around the accretor, which can exchange angular momentum and cause a more rapid loss of orbital angular momentum. In the simulations presented here, the effect of the ideal equation of state is to de-stabilize the binary in both SPH and grid simulations, but the effect is more pronounced in the grid code.
- OSTI ID:
- 22661215
- Journal Information:
- Astrophysical Journal, Supplement Series, Journal Name: Astrophysical Journal, Supplement Series Journal Issue: 2 Vol. 229; ISSN 0067-0049; ISSN APJSA2
- Country of Publication:
- United States
- Language:
- English
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