Hydrodynamic Modeling of Low-Mass White Dwarf Mergers
Board Location: #77
Discipline: Physics
Session: 1
Eva Christina Cullen - Columbia University
Co-Author(s): Rafe Wilkinson, University of Delaware, Newark, DE Stanley Owocki, University of Delaware, Newark, DE
Hypothesis: The merger of two low-mass white dwarfs in an unstable triple system can result in the formation of a very luminous, low-mass Wolf-Rayet star. This research explores a novel pathway for the creation of these rare stellar objects and extends our understanding of stellar evolution in multiple star systems.
Recent models suggest that stellar mergers within unstable triple systems can lead to dramatic eruptions, as evidenced by the 1840s event of Eta Carinae. Similarly, luminous red novae are now thought to result from such mergers. This study aims to investigate whether a similar mechanism could explain the existence of certain Wolf-Rayet stars, specifically those with low mass but high luminosity.
Methods: We will adapt hydrodynamic codes previously developed for modeling the Eta Carinae merger to simulate the merger of two low-mass white dwarfs. The key challenge lies in modifying these codes to account for the degenerate nature of white dwarfs. We will run multiple simulations with varying initial conditions, including different mass ratios and orbital parameters. Control simulations will be performed using non-degenerate stellar models to isolate the effects of degeneracy on the merger process.
Results: We anticipate that the simulations will reveal the complex hydrodynamics of white dwarf mergers, including the mixing of stellar material, energy release, and potential mass loss. We expect to observe significant differences between the degenerate and non-degenerate merger simulations, particularly in terms of the timescales and energetics of the process.
The analysis will provide predictions for the physical characteristics of the merger product, including its mass, luminosity, temperature, and composition. These properties will be compared to observations of known low-mass, high-luminosity Wolf-Rayet stars to assess the viability of this formation scenario.
Conclusions and Future Research: This study will provide insights into a potential formation channel for unusual Wolf-Rayet stars and contribute to our broader understanding of stellar mergers and their outcomes. The results will help constrain the conditions under which white dwarf mergers could lead to the formation of Wolf-Rayet stars.
Future research questions may include:
How do the properties of the merger product evolve over time, and what are the implications for the long-term fate of these objects?
Can this merger scenario explain other types of unusual stellar objects?
What are the rates of such mergers, and how do they contribute to the overall population of Wolf-Rayet stars?
How might the presence of a third star in the system affect the merger process and its outcome?
Funder Acknowledgement(s): Columbia University Valentini Fund
Faculty Advisor: Stanley Owocki, owocki@udel.edu
Role: As a student researcher, I ran hydrodynamic simulations of low-mass white dwarf mergers using adapted code accounting for degenerate matter. I executed multiple simulations with varying initial conditions. I developed analysis code in Python and Mathematica to process the simulation outputs, focusing on the physical properties of merger products. My analysis examined key parameters like mass, luminosity, temperature, and composition. I compared our results with observational data of known low-mass, high-luminosity Wolf-Rayet stars to assess our formation scenario's viability. I also ran control simulations with non-degenerate models to isolate degeneracy effects. Throughout the project, I worked closely with faculty to interpret results and discuss implications for stellar evolution in multiple star systems.