A localised subgrid scale model for fluid dynamical simulations in astrophysics

Schmidt, Wolfgang; Niemeyer, J. C.; Hillebrandt, W.; Röpke, F. K.

doi:10.1051/0004-6361:20053618

Cited by 120 publications

(93 citation statements)

References 47 publications

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“…We note that the sub-grid scale energy, which is of the order of 10 47 to 10 48 erg in turbulent deflagrations, is neglected here (see Fig. 1 in Schmidt et al 2006b). Figure 3a shows model GCD200, while Fig.…”

Section: High-resolution Simulation Of Model Gcd200mentioning

confidence: 99%

Three-dimensional simulations of gravitationally confined detonations compared to observations of SN 1991T

Seitenzahl

Kromer

Ohlmann

et al. 2016

A&A

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The gravitationally confined detonation (GCD) model has been proposed as a possible explosion mechanism for Type Ia supernovae in the single-degenerate evolution channel. It starts with ignition of a deflagration in a single off-centre bubble in a near-Chandrasekharmass white dwarf. Driven by buoyancy, the deflagration flame rises in a narrow cone towards the surface. For the most part, the main component of the flow of the expanding ashes remains radial, but upon reaching the outer, low-pressure layers of the white dwarf, an additional lateral component develops. This causes the deflagration ashes to converge again at the opposite side, where the compression heats fuel and a detonation may be launched. We first performed five three-dimensional hydrodynamic simulations of the deflagration phase in 1.4 M carbon/oxygen white dwarfs at intermediate-resolution (256 3 computational zones). We confirm that the closer the initial deflagration is ignited to the centre, the slower the buoyant rise and the longer the deflagration ashes takes to break out and close in on the opposite pole to collide. To test the GCD explosion model, we then performed a high-resolution (512 3 computational zones) simulation for a model with an ignition spot offset near the upper limit of what is still justifiable, 200 km. This high-resolution simulation met our deliberately optimistic detonation criteria, and we initiated a detonation. The detonation burned through the white dwarf and led to its complete disruption. For this model, we determined detailed nucleosynthetic yields by post-processing 10 6 tracer particles with a 384 nuclide reaction network, and we present multi-band light curves and time-dependent optical spectra. We find that our synthetic observables show a prominent viewing-angle sensitivity in ultraviolet and blue wavelength bands, which contradicts observed SNe Ia. The strong dependence on the viewing angle is caused by the asymmetric distribution of the deflagration ashes in the outer ejecta layers. Finally, we compared our model to SN 1991T. The overall flux level of the model is slightly too low, and the model predicts pre-maximum light spectral features due to Ca, S, and Si that are too strong. Furthermore, the model chemical abundance stratification qualitatively disagrees with recent abundance tomography results in two key areas: our model lacks low-velocity stable Fe and instead has copious amounts of high-velocity 56 Ni and stable Fe. We therefore do not find good agreement of the model with SN 1991T.

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Section: High-resolution Simulation Of Model Gcd200mentioning

confidence: 99%

Three-dimensional simulations of gravitationally confined detonations compared to observations of SN 1991T

Seitenzahl

Kromer

Ohlmann

et al. 2016

A&A

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“…On the one hand, the conditions under which the thermonuclear runaway commences remain poorly understood so that the initial number and distribution of flamelets that seed the runaway is still a free parameter. On the other hand, although significant progress has been made in simulating flame fronts in multidimensional stellar models (see García-Senz & Bravo 2005;Gamezo et al 2005;Schmidt et al 2006b;Röpke et al 2007a;Townsley et al 2007;Jordan et al 2008, for recent examples from several groups), the challenge associated with modeling an unresolved turbulent deflagration (e.g., Schmidt et al 2006a) with limited computational resources injects an additional degree of uncertainty into the outcome of a model for any given choice of initial conditions. Readers are referred to Hillebrandt & Niemeyer (2000) for a review of the challenges associated with modeling and validating the SNe Ia explosion mechanism, and Röpke (2006) for an update on the state of multidimensional modeling.…”

Section: Introductionmentioning

confidence: 99%

STUDY OF THE DETONATION PHASE IN THE GRAVITATIONALLY CONFINED DETONATION MODEL OF TYPE Ia SUPERNOVAE

Meakin

Seitenzahl

Townsley

et al. 2009

ApJ

100

118

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We study the gravitationally confined detonation (GCD) model of Type Ia supernovae (SNe Ia) through the detonation phase and into homologous expansion. In the GCD model, a detonation is triggered by the surface flow due to single-point, off-center flame ignition in carbon-oxygen white dwarfs (WDs). The simulations are unique in terms of the degree to which nonidealized physics is used to treat the reactive flow, including weak reaction rates and a time-dependent treatment of material in nuclear statistical equilibrium (NSE). Careful attention is paid to accurately calculating the final composition of material which is burned to NSE and frozen out in the rapid expansion following the passage of a detonation wave over the high-density core of the WD; and an efficient method for nucleosynthesis postprocessing is developed which obviates the need for costly network calculations along tracer particle thermodynamic trajectories. Observational diagnostics are presented for the explosion models, including abundance stratifications and integrated yields. We find that for all of the ignition conditions studied here a self-regulating process comprised of neutronization and stellar expansion results in final 56 Ni masses of ∼1.1 M . But, more energetic models result in larger total NSE and stable Fe-peak yields. The total yield of intermediate mass elements is ∼ 0.1 M and the explosion energies are all around 1.5 × 10 51 erg. The explosion models are briefly compared to the inferred properties of recent SN Ia observations. The potential for surface detonation models to produce lower-luminosity (lower 56 Ni mass) SNe is discussed.

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“…We used the N100 model from the set of three-dimensional delayed detonation simulations carried out by Seitenzahl et al (2013) with the thermonuclear supernova code L. For a detailed description of the applied techniques we refer the reader to Reinecke et al (1999), Röpke & Hillebrandt (2005), Schmidt et al (2006), Röpke & Niemeyer (2007), and to references therein.…”

Section: Explosion Modelsmentioning

confidence: 99%

Gamma-ray diagnostics of Type Ia supernovae

Summa

Ulyanov

Kromer

et al. 2013

A&A

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Context. Although the question of progenitor systems and detailed explosion mechanisms still remains a matter of discussion, it is commonly believed that Type Ia supernovae (SNe Ia) are production sites of large amounts of radioactive nuclei. Even though the gamma-ray emission due to radioactive decays is responsible for powering the light curves of SNe Ia, gamma rays themselves are of particular interest as a diagnostic tool because they directly lead to deeper insight into the nucleosynthesis and the kinematics of these explosion events. Aims. We study the evolution of gamma-ray line and continuum emission of SNe Ia with the objective of analyzing the relevance of observations in this energy range. We seek to investigate the chances for the success of future MeV missions regarding their capabilities for constraining the intrinsic properties and the physical processes of SNe Ia. Methods. Focusing on two of the most broadly discussed SN Ia progenitor scenarios -a delayed detonation in a Chandrasekhar-mass white dwarf (WD) and a violent merger of two WDs -we used three-dimensional explosion models and performed radiative transfer simulations to obtain synthetic gamma-ray spectra. Both chosen models produce the same mass of 56 Ni and have similar optical properties that are in reasonable agreement with the recently observed supernova SN 2011fe. We examine the gamma-ray spectra with respect to their distinct features and draw connections to certain characteristics of the explosion models. Applying diagnostics, such as line and hardness ratios, the detection prospects for future gamma-ray missions with higher sensitivities in the MeV energy range are discussed. Results. In contrast to the optical regime, the gamma-ray emission of our two chosen models proves to be quite different. The almost direct connection of the emission of gamma rays to fundamental physical processes occurring in SNe Ia permits additional constraints concerning several explosion model properties that are not easily accessible within other wavelength ranges. Proposed future MeV missions such as GRIPS will resolve all spectral details only for nearby SNe Ia, but hardness ratio and light curve measurements still allow for a distinction of the two different models at 10 Mpc and 16 Mpc for an exposure time of 10 6 s. The possibility of detecting the strongest line features up to the Virgo distance will offer the opportunity to build up a first sample of SN Ia detections in the gamma-ray energy range and underlines the importance of future space observatories for MeV gamma rays.

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A localised subgrid scale model for fluid dynamical simulations in astrophysics

Cited by 120 publications

References 47 publications

Three-dimensional simulations of gravitationally confined detonations compared to observations of SN 1991T

Three-dimensional simulations of gravitationally confined detonations compared to observations of SN 1991T

STUDY OF THE DETONATION PHASE IN THE GRAVITATIONALLY CONFINED DETONATION MODEL OF TYPE Ia SUPERNOVAE

Gamma-ray diagnostics of Type Ia supernovae

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