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

¹ Departament de Física, EEBE, Universitat Politècnica de Catalunya, c/Eduard Maristany 16, E-08019 Barcelona, Spain
² Institut d’Estudis Espacials de Catalunya, c/Esteve Terradas 1, E-08860 Castelldefels, Spain
³ Center for Scientific Computing (sciCORE), Universität Basel, Klingelbergstrasse 61, CH-4056 Basel, Switzerland

^⋆ Corresponding author; jordi.jose@upc.edu

Received: 14 March 2024
Accepted: 6 December 2024

Abstract

Context. Recurrent novae are, by definition, novae observed in outburst more than once. They exhibit notably short recurrence times between outbursts, ranging from 1 to about 100 yr. These short recurrence times require very high mass-accretion rates, white dwarf masses close to the Chandrasekhar mass limit, and very high initial white dwarf luminosities. The likely increase in the white dwarf’s mass after each outburst makes recurrent novae potential type Ia supernova progenitors.

Aims. 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.

Methods. 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.

Results. Simulations reveal complete disruption and sweeping of the accretion disk orbiting the white dwarf star for models with flared disks and M_ejecta/M_disk ≥ 1. In contrast, V-shaped disks with a (constant) high initial density and M_ejecta/M_disk < 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.