Reactive Flow in Nova Outbursts

Glasner, S. Ami; Livne, Eli; Truran, J. W.

doi:10.1086/303561

Cited by 106 publications

(159 citation statements)

References 39 publications

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“…The onset of the instabilities in such an extremely low numerical diffusion regime is substantially delayed. The simulations reported by Glasner et al (1997) A similar behavior is also found for the time required for the convective front to reach the outer boundary, t Y , and for the history of the nuclear energy generation rate (Fig. 4).…”

Section: Effect Of the Grid Resolutionsupporting

confidence: 74%

“…As in Casanova et al (2010), we used the same initial model as Glasner et al (1997) and Kercek et al (1998): a 1 M CO white dwarf that accretes solar composition matter (Z = 0.02) at a rate of 5 × 10 −9 M yr −1 . The model was evolved spherically (1-D) and mapped onto a 2-D cartesian grid, when the temperature at the base of the envelope reached ≈10 8 K. It initially comprised 112 radial layers -including the outermost part of the CO core -and 512 horizontal layers.…”

Section: Input Physics and Initial Conditionsmentioning

confidence: 99%

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Mixing in classical novae: a 2-D sensitivity study

Casanova

José

Garcı́a–Berro

et al. 2011

A&A

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Context. Classical novae are explosive phenomena that take place in stellar binary systems. They are powered by mass transfer from a low-mass, main sequence star onto a white dwarf. The material piles up under degenerate conditions and a thermonuclear runaway ensues. The energy released by the suite of nuclear processes operating at the envelope heats the material up to peak temperatures of ∼(1−4) × 10 8 K. During these events, about 10 −4 −10 −5 M , enriched in CNO and other intermediate-mass elements, are ejected into the interstellar medium. To account for the gross observational properties of classical novae (in particular, a metallicity enhancement in the ejecta above solar values), numerical models assume mixing between the (solar-like) material transferred from the companion and the outermost layers (CO-or ONe-rich) of the underlying white dwarf. Aims. The nature of the mixing mechanism that operates at the core-envelope interface has puzzled stellar modelers for about 40 years. Here we investigate the role of Kelvin-Helmholtz instabilities as a natural mechanism for self-enrichment of the accreted envelope with core material. Methods. The feasibility of this mechanism is studied by means of the multidimensional code FLASH. Here, we present a series of 9 numerical simulations perfomed in two dimensions aimed at testing the possible influence of the initial perturbation (duration, strength, location, and size), the resolution adopted, or the size of the computational domain on the results. Results. We show that results do not depend substantially on the specific choice of these parameters, demonstrating that KelvinHelmholtz instabilities can naturally lead to self-enrichment of the accreted envelope with core material, at levels that agree with observations.

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Section: Effect Of the Grid Resolutionsupporting

confidence: 74%

Section: Input Physics and Initial Conditionsmentioning

confidence: 99%

Mixing in classical novae: a 2-D sensitivity study

Casanova

José

Garcı́a–Berro

et al. 2011

A&A

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“…The free outflow (open) boundary condition used in Eulerian schemes artificially quenches the runaway. Use of such a boundary condition in Eulerian simulations can explain the main differences between the models presented by Glasner et al (1997) and those of Kercek et al (1998). The fact that in the latter simulation virtually all of the hydrogen disappears from the grid at late times ( Fig.…”

Section: Discussionmentioning

confidence: 96%

The Sensitivity of Multidimensional Nova Calculations to the Outer Boundary Condition

Glasner

Livne

Truran

2005

ApJ

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Multidimensional reactive flow models of accreted hydrogen-rich envelopes on top of degenerate cold white dwarfs are very effective tools for the study of critical, nonspherically symmetric behaviors during the early stages of nova outbursts. Such models can shed light on both the mechanism responsible for the heavy-element enrichment observed to characterize nova envelope matter and the role of perturbations during the early stages of ignition of the runaway. The complexity of convective reactive flow in multidimensions makes the computational model itself complex and sensitive to the details of the numerics. In this study, we demonstrate that the imposed outer boundary condition can have a dramatic effect on the solution. Several commonly used choices for the outer boundary conditions are examined. It is shown that the solutions obtained from Lagrangian simulations, where the envelope is allowed to expand and mass is being conserved, are consistent with spherically symmetric solutions. In Eulerian schemes, which utilize an outer boundary condition of free outflow, the outburst can be artificially quenched.

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“…The few multidimensional models of mixing at the coreenvelope interface available to date have proven particularly controversial. Indeed, two independent, two-dimensional studies (Glasner et al 1997;Kercek et al 1998), based upon the same 1-D initial model, reached totally different conclusions about the strength of the runaway and its capability to power a fast nova. The origin of such differences was carefully analyzed by Glasner et al (2005), who concluded that the early stages of the explosion, prior to the onset of the TNR -when the evolution is almost quasi-staticare extremely sensitive to the outer boundary conditions.…”

Section: Multidimensional Nova Models: the Next Frontiermentioning

confidence: 99%

Classical and Recurrent Nova Models

José¹,

Casanova²,

Garcı́a–Berro³

et al. 2011

Proc. IAU

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Abstract. Remarkable progress in the understanding of nova outbursts has been achieved through combined efforts in photometry, spectroscopy and numerical simulations. According to the thermonuclear runaway model, novae are powered by thermonuclear explosions in the hydrogen-rich envelopes transferred from a low-mass stellar companion onto a close white dwarf star. Extensive numerical simulations in 1-D have shown that the accreted envelopes attain peak temperatures ranging between 10 8 and 4 × 10 8 K, for about several hundred seconds, hence allowing extensive nuclear processing which eventually shows up in the form of nucleosynthetic fingerprints in the ejecta. Indeed, it has been claimed that novae can play a certain role in the enrichment of the interstellar medium through a number of intermediate-mass elements. This includes 17 O, 15 N, and 13 C, systematically overproduced with respect to solar abundances, plus a lower contribution in a number of other species (A < 40), such as 7 Li, 19 F, or 26 Al. At the turn of the XXI Century, classical novae have entered the era of multidimensional models, which provide a new insight into the physical mechanisms that drive mixing at the core-envelope interface.In this review, we will present hydrodynamic models of classical novae, from the onset of accretion up to the explosion and ejection stages, both for classical and recurrent novae, with special emphasis on their gross observational properties and their associated nucleosynthesis. The impact of nuclear uncertainties on the final yields will be discussed. Recent results from 2-D models of mixing during classical nova outbursts will also be presented.

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Reactive Flow in Nova Outbursts

Cited by 106 publications

References 39 publications

Mixing in classical novae: a 2-D sensitivity study

Mixing in classical novae: a 2-D sensitivity study

The Sensitivity of Multidimensional Nova Calculations to the Outer Boundary Condition

Classical and Recurrent Nova Models

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