arXiv subjects

Joana Figueira

Publications and source records attributed to Joana Figueira.

4 recordsLinked to original sources

arXiv2026

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

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.

astro-ph.SR↗

arXiv2017

Three-dimensional simulations of the interaction between the nova ejecta, the accretion disk, and the companion star

Context. Classical novae are thermonuclear explosions hosted by accreting white dwarfs in stellar binary systems. Material piles up on top of the white dwarf star under mildly degenerate conditions, driving a thermonuclear runaway. The energy released by the suite of nuclear processes operating at the envelope (mostly proton-capture reactions and beta-decays) heats the material up to peak temperatures ranging from 100 to 400 MK. In these events, about 10-3 - 10-7 Msun, enriched in CNO and, sometimes, other intermediate-mass elements (e.g., Ne, Na, Mg, Al), are ejected into the interstellar medium. Aims. To date, most of the efforts undertaken in the modeling of classical nova outbursts have focused on the early stages of the explosion and ejection, ignoring the interaction of the ejecta, first with the accretion disk orbiting the white dwarf, and ultimately with the secondary star. Methods. A suite of three-dimensional, SPH simulations of the interaction between the nova ejecta, the accretion disk, and the stellar companion have been performed to fill this gap, aimed at testing the influence of the different parameters (i.e., mass and velocity of the ejecta, mass and geometry of the accretion disk) on the dynamical and chemical properties of the system. Results. We discuss the conditions that lead to the disruption of the accretion disk and to mass loss from the binary system. In addition, we discuss the likelihood of chemical contamination of the stellar secondary induced by the impact with the nova ejecta and its potential effect on the next nova cycle.

astro-ph.SR↗

arXiv2017

SPHYNX: an accurate density-based SPH method for astrophysical applications

Hydrodynamical instabilities and shocks are ubiquitous in astrophysical scenarios. Therefore, an accurate numerical simulation of these phenomena is mandatory to correctly model and understand many astrophysical events, such as Supernovas, stellar collisions, or planetary formation. In this work, we attempt to address many of the problems that the smoothed particle hydrodynamics (SPH) technique has when dealing with subsonic hydrodynamical instabilities or shocks. To that aim we built a new SPH code named SPHYNX, that includes many of the recent advances in the SPH technique and some other new ones, which we present here. SPHYNX is of Newtonian type and grounded in the Euler-Lagrange formulation of the SPH technique. Its distinctive features are: the use of an integral approach to estimating the gradients; the use of a flexible family of interpolators called sinc kernels, which suppress pairing instability; and the incorporation of a new type of volume element which provides a better partition of the unity. Unlike other modern formulations, which consider volume elements linked to pressure, our volume element choice relies on density. SPHYNX conserves mass, linear and angular momentum, energy, entropy, and preserves kernel normalization even in strong shocks. The coupling between the integral approach to calculate gradients and the new family of volume elements reduces the so-called tensile instability. Both features help to suppress the damp which often prevents the growth of hydrodynamic instabilities in regular SPH codes. On the whole, SPHYNX has passed the verification tests described below. For identical particle setting and initial conditions the results were similar (or better in some particular cases) than those obtained with other SPH schemes such as GADGET-2, PSPH or with the recent density-independent formulation (DISPH) and conservative reproducing kernel (CRKSPH) techniques.

astro-ph.IM↗

arXiv2013

The evolution of triples with a Roche-lobe filling outer star

The evolution of triples has not attracted much attention in the literature, although their evolution can be dramatically different from binaries and single stars. Triples are quite common, and we find that for about 1% of the triples in the Tokovinin catalogue of multiple stellar systems in the solar neighbourhood, the tertiary star will overflow its Roche lobe at some time in its evolution, before any of the inner stars leave the main sequence. For two of these systems, Xi Tauri and HD97131 we simulate in detail this phase of mass transfer, during which stellar evolution, gravitational dynamics and hydrodynamics all play an important role. We have used the Astrophysical Multi-purpose Software Environment (AMUSE) to solve these physical processes in a self-consistent way. The resulting evolution, mass transfer and the effects on the inner as well as on the outer orbit are profound, although it is not trivial to predict the eventual consequence of the phase of mass transfer and the appearance of the resulting system.

astro-ph.SR↗