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C. van Der Merwe, S. Mohamed, J. José, M. Shara and T. Kaminski, 2024
Stellar collisions have garnered renewed attention for their role in the formation of peculiar objects, such as blue stragglers, and their potential to explain transients with atypical observational and spectroscopic signatures. Among these, white dwarf-main sequence (WD-MS) collisions are particularly intriguing due to the diverse evolutionary pathways they can produce—such as peculiar red giants, novae, or sub-Chandrasekhar supernovae. We present 3D smoothed particle hydrodynamics (SPH) simulations of WD-MS collisions, exploring a range of mass ratios and impact parameters. We analyze the dynamics, energetics, gas morphology, and mass loss from these interactions. Using a 34-isotope nuclear network, we further predict the nucleosynthesis products generated during these collisions. Our models suggest that enriched 13C, 15N, and 17O, may be observable both in the ejecta, organised as a bipolar structure, and on the surface of the stellar remnant. In the case of a near head-on collision, an overabundance of 7Li relative to solar values may be detected both in the ejecta and on the stellar remnant surface.
White Dwarf-Main Sequence Collisions
Collision between a 0.3Msun MS star and a 0.6Msun WD
q05_dmin025.mp4Temperature (top) and density (bottom) cross-sections through the collision axis of the interaction (model q05_dmin025). The trajectories are calculated such that the periastron distance between the stars (if represented by point-masses) would be dmin = 0.25(R_MS+R_WD). Impact velocity is v_imp ~ 1000 km/s.
q05_dmin05.mp4Temperature (top) and density (bottom) cross-sections through the collision axis of the interaction (model q05_dmin05). The trajectories are calculated such that the periastron distance between the stars (if represented by point-masses) would be dmin = 0.5(R_MS+R_WD). Impact velocity is v_imp ~ 1000 km/s.
q05_dmin025_split.mp43D rendering of model q05_dmin025, sliced so that only the lower hemispheres of the stars are shown. The trajectories are calculated such that the periastron distance between the stars (if represented by point-masses) would be dmin = 0.25(R_MS+R_WD). The impact velocity v_imp ~ 1000 km/s.
Collision between a 0.6Msun MS star and a 0.6Msun WD
q1_dmin05.mp4Temperature (top) and density (bottom) cross-sections in the xy-plane (model q1_dmin05). The trajectories are calculated such that the periastron distance between the stars (if represented by point-masses) would be dmin = 0.5(R_MS+R_WD). Impact velocity is v_imp ~ 900 km/s.
q1_dmin025.mp4Temperature (top) and density (bottom) cross-sections in the xy-plane (model q1_dmin025). The trajectories are calculated such that the periastron distance between the stars (if represented by point-masses) would be dmin = 0.25(R_MS+R_WD). Impact velocity is v_imp ~ 900 km/s.
q1_dmin025_xy_N15_contours.mp4Temperature cross-sections through the xy-plane (model q1_dmin025). This animation shows the evolution of the N15 isotope (contours), which eventually forms a bi-polar structure.
q1_dmin025_zy_N15_contours_zoomed_out.mp4Temperature cross-section through the zy-plane (model q1_dmin025). This animation shows the evolution of the N15 isotope (contours) which eventually forms a bi-polar structure.
q1_dmin025_zy_N15_contours.mp4Temperature cross-sections through the zy-plane (model q1_dmin025), zoomed in compared to the previous video (on the left column, 3rd row). This movie shows the evolution of the N15 isotope (contours).
q1_dmin025_xz_N15_contours.mp4Temperature cross-sections through the zx-plane (model q1_dmin025). This movie shows the evolution of the N15 isotope (contours).
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