Interaction between the ejecta, the accretion disk, and the secondary star in the recurrent nova system U Sco

TL;DR

This study uses 3D hydrodynamic simulations to investigate how nova ejecta interact with the accretion disk and secondary star in the U Sco system, revealing conditions for disk disruption and minimal contamination of the secondary.

Contribution

First detailed 3D simulation of ejecta-disk-star interactions in recurrent nova U Sco, exploring effects of various parameters on system dynamics.

Findings

Complete disruption of flared accretion disks for high ejecta-to-disk mass ratios.

Partial survival of V-shaped disks with high initial density.

Minimal chemical contamination of the secondary star from ejecta.

Abstract

Most efforts in the modeling of recurrent novae have centered on the initial phases of the explosion and ejection, overlooking the subsequent interaction of the ejecta, first with the accretion disk orbiting the white dwarf and ultimately with the secondary star. To address this gap, a series of 3D smoothed-particle hydrodynamics simulations was conducted. These simulations explored the dynamic interactions between the nova ejecta, accretion disk, and stellar companion within the framework of the recurrent nova system U Sco. Notably, the simulations incorporate rotation around the system's center of mass. The primary goal of these simulations was to qualitatively examine the impact of various model parameters, including ejecta mass, velocity, and density, as well as the mass and geometry of the accretion disk. Simulations reveal complete disruption and sweeping of the accretion disk orbiting the white dwarf star for models with flared disks and Mejecta/Mdisk larger than 1. In contrast, V-shaped disks with a (constant) high initial density and Mejecta/Mdisk < 1 partially survive the impact with the nova ejecta. A very minor chemical contamination of the secondary star is anticipated in the U Sco case based on the limited impact of nova ejecta particles on the subgiant in all simulations. Minor mass ejection from the subgiant's outer layers is observed during the late-stage collision with ejecta and disk material, with some particles ejected from the binary system and some accreted by the white dwarf.