A master thesis from Aalborg University
From Cataclysmic Variables to AM CVn Systems: Modeling LISA Gravitational Wave Sources Using MESA
Term
4. term (FYS10)
Education
Publication year
2025
Submitted on
2025-05-30
Pages
72 pages
Abstract
The aim of this thesis is to simulate AM~CVn binaries, using the cataclysmic variable formation channel to provide insight into the expected gravitational strain amplitudes of AM~CVns and the detectability with respect to THE Laser Interferometer Space Antenna (LISA). Relevant physics including mass transfer, novae eruptions, magnetic braking and gravitational wave radiation is presented to give an overview of the different effects, which play a role in the evolution of these systems. The convection and rotation boosted (CARB) magnetic braking prescription is used. Furthermore, the strain amplitude of the gravitational wave signal and the LISA sensitivity curves were included to evaluate the gravitational signal received from these binaries. Modules for Experiments in Stellar Astrophysics, MESA, version 24.08.1 is used to simulate the evolution of these systems, implementing the presented physics. To evaluate the simulations, we found observational data for AM CVn systems to use as benchmarks, and evolved CV systems. The latter were included such that we can determine whether we also are able to reproduce these, which is required following the assumed evolution. We found that it is possible to reproduce known AM~CVn systems, assuming this CV evolutionary channel. Furthermore, our simulated systems shows strong gravitational wave signals and most are detectable with LISA, once operational. The CARB magnetic braking model was found to have a strong impact on the evolution of these AM~CVn systems. The initial parameter fine-tuning was resolved by using this stronger model. However, this model also caused our simulated systems to yield higher mass transfer rates than that of the observational data in the AM~CVn phase. Turning of magnetic braking for the compact donors yielded better results, however during so caused too low mass transfer rates. Thus another prescription is needed for compact donors in order to reproduce more observed systems.
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