Deflagration Model Research Articles

Including a luminous central remnant in radiative transfer simulations for type iax supernovae

Abstract Type Iax supernovae (SNe Iax) are proposed to arise from deflagrations of Chandrasekhar mass white dwarfs. Previous deflagration simulations have achieved good agreement with the light curves and spectra of intermediate-luminosity and bright SNe Iax. However, the model light curves decline too quickly after peak, particularly in red optical and NIR bands. Deflagration models with a variety of ignition configurations do not fully unbind the white dwarf, leaving a remnant polluted with 56Ni. Emission from such a remnant may contribute to the luminosity of SNe Iax. Here we investigate the impact of adding a central energy source, assuming instantaneous powering by 56Ni decay in the remnant, in radiative transfer calculations of deflagration models. Including the remnant contribution improves agreement with the light curves of SNe Iax, particularly due to the slower post-maximum decline of the models. Spectroscopic agreement is also improved, with intermediate-luminosity and faint models showing greatest improvement. We adopt the full remnant 56Ni mass predicted for bright models, but good agreement with intermediate-luminosity and faint SNe Iax is only possible for remnant 56Ni masses significantly lower than those predicted. This may indicate that some of the 56Ni decay energy in the remnant does not contribute to the radiative luminosity but instead drives mass ejection, or that escape of energy from the remnant is significantly delayed. Future work should investigate the structure of remnants predicted by deflagration models and the potential roles of winds and delayed energy escape, as well as extend radiative transfer simulations to late times.

Observational Properties of a Bright Type lax SN 2018cni and a Faint Type Iax SN 2020kyg

We present the optical photometric and spectroscopic analysis of two Type Iax supernovae (SNe), 2018cni and 2020kyg. SN 2018cni is a bright Type Iax SN (M V,peak = −17.81 ± 0.21 mag), whereas SN 2020kyg (M V,peak = −14.52 ± 0.21 mag) is a faint one. We derive 56Ni mass of 0.07 and 0.002 M ⊙ and ejecta mass of 0.48 and 0.14 M ⊙ for SNe 2018cni and 2020kyg, respectively. A combined study of the bright and faint Type Iax SNe in R/r-band reveals that the brighter objects tend to have a longer rise time. However, the correlation between the peak luminosity and decline rate shows that bright and faint Type Iax SNe exhibit distinct behavior. Comparison with standard deflagration models suggests that SN 2018cni is consistent with the deflagration of a CO white dwarf, whereas the properties of SN 2020kyg can be better explained by the deflagration of a hybrid CONe white dwarf. The spectral features of both the SNe point to the presence of similar chemical species but with different mass fractions. Our spectral modeling indicates stratification at the outer layers and mixed inner ejecta for both of the SNe.

SN 2020udy: an SN Iax with strict limits on interaction consistent with a helium-star companion

ABSTRACT Early observations of transient explosions can provide vital clues to their progenitor origins. In this paper, we present the nearby Type Iax (02cx-like) supernova (SN), SN 2020udy, that was discovered within hours (∼7 h) of estimated first light. An extensive data set of ultra-violet, optical, and near-infrared observations was obtained, covering out to ∼150 d after explosion. SN 2020udy peaked at −17.86 ± 0.43 mag in the r band and evolved similarly to other ‘luminous’ SNe Iax, such as SNe 2005hk and 2012Z. Its well-sampled early light curve allows strict limits on companion interaction to be placed. Main-sequence companion stars with masses of 2 and 6 M⊙ are ruled out at all viewing angles, while a helium-star companion is allowed from a narrow range of angles (140–180° away from the companion). The spectra and light curves of SN 2020udy are in good agreement with those of the ‘N5def’ deflagration model of a near Chandrasekhar-mass carbon–oxygen white dwarf. However, as has been seen in previous studies of similar luminosity events, SN 2020udy evolves slower than the model. Broad-band linear polarization measurements taken at and after peak are consistent with no polarization, in agreement with the predictions of the companion-star configuration from the early light-curve measurements. The host galaxy environment is low metallicity and is consistent with a young stellar population. Overall, we find the most plausible explosion scenario to be the incomplete disruption of a CO white dwarf near the Chandrasekhar-mass limit, with a helium-star companion.

An approach for an extension of the deflagration model in containment code system COCOSYS to separate burned and unburned atmosphere via junctions

Abstract In case of a postulated severe accident in a water-cooled nuclear power plant significant amounts of hydrogen (H2) and carbon monoxide (CO) can be generated and released into the containment or reactor building where it might form a combustible mixture with air assuming passive autocatalytic recombiners are not available. In case of ignition, pressure peaks might occur, that are relevant for the integrity of safety relevant equipment and the containment or reactor building. It is therefore important for safety analysis to be able to correctly predict combustion phenomena that might occur. The accident analysis code AC2 2021.0 which is developed by Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) includes the Containment Code System (COCOSYS version 3.1) for the simulation of containment phenomena. COCOSYS contains the model FRONT for the simulation of premixed deflagration of H2 and CO. Recent code validation using H2 deflagration tests conducted in the multi-compartment THAI+ test facility shows that the flame propagation stops prematurely in simulations of some tests. This is partly attributed to the missing separation of burned and unburned atmosphere which leads to a reduction in fuel concentration in not yet burning zones connected to a burning zone. Model improvement potential was identified which is addressed in this paper. A model extension to separate burned and unburned atmosphere via a junction model is proposed and implemented into a development version of COCOSYS 3.1. First validation results using the THAI test HD-39 are discussed that show improved prediction capability by the extended model.

Early-time spectroscopic modelling of the transitional Type Ia Supernova 2021rhu with tardis

ABSTRACT An open question in SN Ia research is where the boundary lies between ‘normal’ Type Ia supernovae (SNe Ia) that are used in cosmological measurements and those that sit off the Phillips relation. We present the spectroscopic modelling of one such ‘86G-like’ transitional SN Ia, SN 2021rhu, that has recently been employed as a local Hubble Constant calibrator using a tip of the red-giant branch measurement. We detail its modelling from −12 d until maximum brightness using the radiative-transfer spectral-synthesis code tardis. Please check and correct this paper accordingly. We base our modelling on literature delayed-detonation and deflagration models of Chandrasekhar mass white dwarfs, as well as the double-detonation models of sub-Chandrasekhar mass white dwarfs. We present a new method for ‘projecting’ abundance profiles to different density profiles for ease of computation. Due to the small velocity extent and low outer densities of the W7 profile, we find it inadequate to reproduce the evolution of SN 2021rhu as it fails to match the high-velocity calcium components. The host extinction of SN 2021rhu is uncertain but we use modelling with and without an extinction correction to set lower and upper limits on the abundances of individual species. Comparing these limits to literature models we conclude that the spectral evolution of SN 2021rhu is also incompatible with double-detonation scenarios, lying more in line with those resulting from the delayed-detonation mechanism (although there are some discrepancies, in particular a larger titanium abundance in SN 2021rhu compared to the literature). This suggests that SN 2021rhu is likely a lower luminosity, and hence lower temperature, version of a normal SN Ia.

Theoretical Analysis and Numerical Simulation of the Motion of RDX Deflagration-Driven Flyer Plate Based on Laser-Initiated Micro-Pyrotechnic Devices.

Miniaturized laser-initiated pyrotechnic devices have great application prospects in aerospace and modern weapon systems due to their excellent energy output performance and reliability. In order to develop a low-energy insensitive laser detonation technology based on a two-stage charge structure, it is important to deeply analyze the motion law of a titanium flyer plate driven by the deflagration of the first-stage charge (RDX). The effects of the charge mass of RDX, flyer plate mass, and barrel length on the motion law of flyer plates were studied through a numerical simulation method based on the Powder Burn deflagration model. The consistency between the numerical simulation and the experimental results was analyzed using the paired t confidence interval estimation method. The results show that the Powder Burn deflagration model can effectively describe the motion process of the RDX deflagration-driven flyer plate with a 90% confidence level, and its velocity error is ≤6.7%. The speed of the flyer plate is proportional to the mass of the RDX charge, inversely proportional to the mass of the flyer plate, and exponentially related to its moving distance. As the moving distance of the flyer plate increases, the RDX deflagration products and air in front of the flyer plate are compressed, which inhibits the motion of the flyer plate. In the optimum state (the mass of the RDX charge is 60 mg, the mass of the flyer is 85 mg, and the length of the barrel is 3 mm), the speed of the titanium flyer reaches 583 m/s, and the peak pressure of the RDX deflagration reaches 2182 MPa. This work will provide a theoretical basis for the refined design of a new generation of miniaturized high-performance laser-initiated pyrotechnic devices.

Optical studies of a bright Type Iax supernova SN 2020rea

ABSTRACTWe present optical photometric and spectroscopic analysis of a Type Iax supernova (SN) 2020rea situated at the brighter luminosity end of Type Iax supernovae (SNe). The light curve decline rate of SN 2020rea is Δm15(g) = 1.31 ± 0.08 mag which is similar to SNe 2012Z and 2005hk. Modelling the pseudo-bolometric light curve with a radiation diffusion model yields a mass of 56Ni of 0.13 ± 0.01 M⊙ and an ejecta mass of 0.77$^{+0.11}_{-0.21}$ M⊙. Spectral features of SN 2020rea during the photospheric phase show good resemblance with SN 2012Z. TARDIS modelling of the early spectra of SN 2020rea reveals a dominance of Iron Group Elements (IGEs). The photospheric velocity of the Si ii line around maximum for SN 2020rea is ∼ 6500 km s−1 which is less than the measured velocity of the Fe ii line and indicates significant mixing. The observed physical properties of SN 2020rea match with the predictions of pure deflagration model of a Chandrasekhar mass C–O white dwarf. The metallicity of the host galaxy around the SN region is 12 + log(O/H) = 8.56 ± 0.18 dex which is similar to that of SN 2012Z.

Ventdef: A new engineering model for vented gas deflagration based on NFPA 68 (2018)

AbstractHydrogen production and storage equipment are often located inside confined enclosures such as containers or buildings. Deflagration vent panels are one of the most common and simplest methods to mitigate the consequences of gas deflagrations in confined systems. There are well‐established methods for sizing vent panels, such as the National Fire Protection Association standard NFPA 68, but these are often challenging to apply to hydrogen (a highly reactive gas) if the conservative worst stoichiometric fuel/air concentration is used. This paper presents a new engineering model, Ventdef, based on NFPA 68 (2018) and applied section 7.2.3.2 in NFPA 68 (2018) for the calculations of Su and Pmax using actual gas concentrations. In addition, Ventdef also predicts overpressure external to the deflagration vent and has a new, less conservative method for predicting the size of the external fireball. The model is validated against a series of recent full‐scale hydrogen confined volume deflagration tests performed under the EU‐funded project “Improving hydrogen safety for energy applications through pre‐normative research on vented deflagrations” (HySEA). Since the modifications to NFPA 68 are based on combustion fundamentals, the approach should be equally applicable to other flammable gases.

Type Ia supernova ejecta–donor interaction: explosion model comparison

ABSTRACT In the single-degenerate scenario of Type Ia supernovae (SNe Ia), the interaction between high-speed ejected material and the donor star in a binary system is expected to lead to mass being stripped from the donor. A series of multidimensional hydrodynamical simulations of ejecta–donor interaction have been performed in previous studies most of which adopt either a simplified analytical model or the W7 model to represent a normal SN Ia explosion. Whether different explosion mechanisms can significantly affect the results of ejecta–donor interaction is still unclear. In this work, we simulate hydrodynamical ejecta interactions with a main-sequence (MS) donor star in two dimensions for two near-Chandrasekhar-mass explosion models of SNe Ia, the W7 and N100 models. We find that about 0.30 and $0.37\, \mathrm{M}_{\odot }$ of hydrogen-rich material are stripped from a $2.5\, \mathrm{M}_\odot$ donor star in a 2 d orbit by the SN Ia explosion in simulations with the W7 deflagration and N100 delayed-detonation explosion model, respectively. The donor star receives a kick of about 74 and $86\, \mathrm{km}\, \mathrm{s}^{-1}$, respectively, in each case. The modal velocity, about $500\, \mathrm{km}\, \mathrm{s}^{-1}$, of stripped hydrogen-rich material in the N100 model is faster than the W7 model, with modal velocity of about $350\, \mathrm{km\, s^{-1}}$, by a factor 1.4. Based on our results, we conclude that the choice of near-Chandrasekhar-mass explosion model for normal SNe Ia seems to not significantly alter the ejecta–donor interaction for a given MS donor model, at least in 2D.

Models of pulsationally assisted gravitationally confined detonations with different ignition conditions

Over the past decades, many explosion scenarios for Type Ia supernovae have been proposed and investigated including various combinations of deflagrations and detonations in white dwarfs of different masses up to the Chandrasekhar mass. One of these is the gravitationally confined detonation model. In this case a weak deflagration burns to the surface, wraps around the bound core, and collides at the antipode. A subsequent detonation is then initiated in the collision area. Since the parameter space for this scenario, that is, varying central densities and ignition geometries, has not been studied in detail, we used pure deflagration models of a previous parameter study dedicated to Type Iax supernovae as initial models to investigate the gravitationally confined detonation scenario. We aim to judge whether this channel can account for one of the many subgroups of Type Ia supernovae, or even normal events. To this end, we employed a comprehensive pipeline for three-dimensional Type Ia supernova modeling that consists of hydrodynamic explosion simulations, nuclear network calculations, and radiative transfer. The observables extracted from the radiative transfer are then compared to observed light curves and spectra. The study produces a wide range in masses of synthesized 56Ni ranging from 0.257 to 1.057 M⊙, and, thus, can potentially account for subluminous as well as overluminous Type Ia supernovae in terms of brightness. However, a rough agreement with observed light curves and spectra can only be found for 91T-like objects. Although several discrepancies remain, we conclude that the gravitationally confined detonation model cannot be ruled out as a mechanism to produce 91T-like objects. However, the models do not provide a good explanation for either normal Type Ia supernovae or Type Iax supernovae.

Investigation of the Prompt SNe Ia progenitor nature through the analysis of the chemical composition of globular clusters and circumgalactic clouds

ABSTRACT A method is proposed for determining the properties of Type Ia supernovae from short-lived precursors – Prompt SNIa. This method is based on the assumption that this subtype of Type Ia supernovae exploded into low-metallicity globular clusters (GCs), and is responsible for the enrichment of the high-metallicity subgroup of GCs and circumgalactic clouds (CGCs) with the iron peak elements. We justify that CGCs are the formation places of GCs of both subgroups. The accuracy of the method depends, first, on the number of GCs, the spectra of which have been studied in detail, and second, on the number of chemical elements, the abundances of which have been worked out. Only those elements are of interest for this method that are produced in supernova explosions and are not produced at the previous stage of the stellar evolution. Our estimates of nucleosynthesis in low-metallicity supernova GCs are in the best agreement with the following Prompt SNIa model: Single Degenerate Pure Deflagration Models of white dwarfs (WDs) burning with masses in the range from $\rm 1.30$ to $1.31\, {\rm M}_{\odot}$ if carbon explodes in the centre of a WD with a low central density from $\rm 0.5 \times 10^9$ to $\rm 10^9\, {\rm g\,cm^{-3}}$ (Leung & Nomoto 2018).

Prediction of concentration of toxic gases produced by detonation of commercial explosives by thermochemical equilibrium calculations

An adverse effect resulting from explosive mine blasts is the production of toxic nitrogen oxides (NO and NO2) and carbon monoxide (CO). The empirical measurements of the concentration of toxic gases showed that it depends not only on the composition of an explosive and properties of its ingredients but also on several other parameters, such as volume of blasting chamber, explosive charge mass and design, confinement characteristics, surrounding atmosphere, etc. That explains why measured concentrations of toxic gases reported in literature significantly differ.In this paper, we discuss the possibility of theoretical prediction of the concentration of toxic gases by thermochemical equilibrium calculation applying two models: ideal detonation model and deflagration model. It can be demonstrated that thermochemical calculations can provide a good estimation of the measured concentrations and reproduce experimentally obtained effects of additives on the production of toxic gases. It was also found that the ideal detonation model applies to heavily confined explosive charges, while the deflagration model is more suitable for low detonation velocity explosives with light confinement.

An analysis of the spectroscopic signatures of layering in the ejecta of Type Iax supernovae

ABSTRACT Investigations of some Type Iax supernovae (SNe Iax) have led to the suggestion that their ejecta must be layered to some degree. Such an ejecta structure has been argued as inconsistent with the well-mixed composition predicted by pure deflagrations. Based on explosion models, we create toy models in which the ejecta are artificially stratified and progressively mixed until a uniform composition is obtained. We find that models that are heavily mixed, containing burned and unburned material at all velocities, produce reasonably good agreement with SN 2012Z, for which a layered structure has been suggested. We also discuss how existing ejecta compositions determined for SNe Iax do not necessarily contradict pure deflagration models and may be consistent with a steeper density profile. We investigate previous claims that differences in line profile shapes may be due to strong blending, by presenting a series of models with different plasma states. These models indicate that blending could indeed explain differences in the observed profiles. Alternatively, stratification could also explain such differences; however, all of our models indicate that this does not necessarily require stratification in abundance. Sufficient stratification in the ionization state can be achieved even for a well-mixed model. Based on our analysis, we demonstrate that there is insufficient evidence to suggest the ejecta of SNe Iax must be layered and therefore argue the pure deflagration scenario is not ruled out, even for the brightest SNe Iax. Our analysis does not indicate the ejecta cannot be layered to some degree, but observations within days of explosion are necessary to determine the extent to which the outer ejecta could be layered.

Intermediate luminosity type Iax supernova 2019muj with narrow absorption lines: Long-lasting radiation associated with a possible bound remnant predicted by the weak deflagration model

Abstract We present comprehensive spectroscopic and photometric analyses of the intermediate luminosity type Iax supernova (SN Iax) 2019muj based on multi-band datasets observed through the framework of the OISTER target-of-opportunity program. SN 2019muj exhibits almost identical characteristics to the subluminous SNe Iax 2008ha and 2010ae in terms of the observed spectral features and the light curve evolution at the early phase, except for the peak luminosity. The long-term observations unveil late-time flattening light curves as seen in luminous SN Iax 2014dt. This can be explained by the existence of an inner dense and optically thick component possibly associated with a bound white dwarf remnant left behind after the explosion. We demonstrate that the weak deflagration model with a wide range of explosion parameters can reproduce the late-phase light curves of other SNe Iax. Therefore, we conclude that a common explosion mechanism operates for different subclass SNe Iax.

A one-dimensional model for deflagration to detonation transition on the tip of elongated flames in tubes.

Deflagration-to detonation transition (DDT) of the tip of self-accelerating elongated front of laminar flames in tubes filled with gas mixtures that are very energetic is studied by employing the one-dimensional model sketched in Fig. 1b. The first part of the present work parallels the nonlinear analysis of the self-similar solution of the double discontinuity model performed by Deshaies and Joulin (1989) (termed DJ herein) in the double limit of weak lead shocks and flame speeds that are very sensitive to the flame temperature. The very energetic mixtures addressed herein exhibit only mild flame-speed dependence on flame temperature but large density ratio so that the critical condition concerns a Mach number of the lead-shock exceeding unity by an amount of order unity. A double-feedback mechanism, in which compressional heating by the lead shock is augmented by an effective piston acceleration due to a back-flow of burnt-gas towards the flame-tip, is shown to yield self-similar solutions that exhibit a turning point at a critical propagation velocity as in DJ but for a lead shock which is not weak. Beyond self-similarity, a further analysis of the upstream-running simple waves generated ahead of the self-accelerating flame then predicts the spontaneous formation of a shock wave on the flame front as a consequence of the finite-time singularity of the acceleration of the flame front at the critical velocity (turning point). Such a shock formation is a good candidate to blow up the inner flame structure, producing the abrupt transition of the flame (a subsonic, quasi-isobaric reaction–diffusion wave) into a detonation (a supersonic compressive wave generating rapid chemical heat release), observed in previously reported experiments, the results of which are consistent with the present scaling.

Delayed Detonation Thermonuclear Supernovae with an Extended Dark Matter Component

Abstract We present spherically symmetric simulations of the thermonuclear explosion of a white dwarf admixed with an extended component of fermionic dark matter, using the deflagration model with the deflagration–detonation transition. In all the dark matter admixed models we have considered, the dark matter is left behind after the explosion as a compact dark star. The presence of dark matter lengthens the deflagration phase to produce a similar amount of iron-group elements and more thermoneutrinos. Dark matter admixed models also give dimmer but slowly declining light curves, consistent with some observed peculiar supernovae. Our results suggest a formation path for dark compact objects that mimic sub-solar-mass black holes as dark gravitational sources.

Prediction of Deflagrative Explosions in Variety of Closed Vessels

In this paper the multi-phenomena deflagration model is used to simulate deflagrative combustion of several fuel–air mixtures in various scale closed vessels. The experimental transient pressure of methane–air, ethane–air, and propane–air deflagrations in vessels of volume 0.02 m3, 1 m3, and 6 m3 were simulated. The model includes key mechanisms affecting propagation of premixed flame front: the dependence of laminar burning velocity of concentration, pressure, and temperature; the effect of preferential diffusion in the corrugated flame front or leading point concept; turbulence generated by flame front itself or Karlovitz turbulence; increase of the flame front area with flame radius by fractals; and turbulence in the unburned mixture. Laminar velocity dependence on concentration, pressure, and temperature were calculated using CANTERA software. Various scale and geometry of used vessels induces various combustion mechanism. Simulations allow insight into the dominating mechanism. The model demonstrated an acceptable predictive capability for a variety of fuels and vessel sizes.

From Supernova to Supernova Remnant: Comparison of Thermonuclear Explosion Models

Abstract Progress in the three-dimensional modeling of supernovae (SNe) prompts us to revisit the supernova remnant (SNR) phase. We continue our study of the imprint of a thermonuclear explosion on the SNR it produces, which we started with a delayed detonation model of a Chandrasekhar-mass white dwarf. Here we compare two different types of explosion models, each with two variants: two delayed detonation models (N100ddt, N5ddt) and two pure deflagration models (N100def, N5def), where the N number parameterizes the ignition. The output of each SN simulation is used as input to an SNR simulation carried on until 500 yr after the explosion. While all SNR models become more spherical over time and overall display the theoretical structure expected for a young SNR, clear differences are visible among the models, depending on the geometry of the ignition and on the presence or not of detonation fronts. Compared to N100 models, N5 models have a strong dipole component and produce asymmetric remnants. N5def produces a regular-looking, but offset remnant, while N5ddt produces a two-sided remnant. Pure deflagration models exhibit specific traits: a central overdensity, because of the incomplete explosion, and a network of seam lines across the surface, boundaries between burning cells. Signatures from the SN dominate the morphology of the SNR up to 100–300 yr after the explosion, depending on the model, and are still measurable at 500 yr, which may provide a way of testing explosion models.

Evaluation of an improved CFD model against nine vented deflagration experiments

In the present work, a newly developed CFD deflagration model incorporated into the ADREA-HF code is evaluated against hydrogen vented deflagrations experiments carried out by KIT and FM-Global in a medium (1 m3) and a real (63.7 m3) scale enclosure respectively. A square vent of 0.5 m2 and 5.4 m2 respectively is located in the center of one of side walls. In the case of the medium scale enclosure the 18% v/v homogeneous hydrogen-air mixture and back-wall ignition case is examined. In the case of the real scale enclosure the examined cases cover different homogeneous mixture concentrations (15% and 18% v/v), different ignition locations (back-wall and center) and different levels of initial turbulence. The CFD model accounts for flame instabilities that develop as the flame propagates inside the chamber and turbulence that mainly develops outside the vent. Pressure predictions are compared against experimental measurements revealing a very good performance of the CFD model for the back-wall ignition cases. For the center ignition cases, the model overestimates the maximum overpressure. The opening of the vent cover is identified as a possible reason for the overprediction. The analysis indicates that turbulence is the main factor which enhances external explosion strength causing the sudden pressure increase, confirming previous findings.

Elemental Abundances in Supernova Remnant W49B as Clues to Its Progenitor

Abstract We apply the Smoothed Particle Inference (SPI) technique to analyze the X-ray emission from SNR W49B. In X-rays, it is visible as a centrally filled supernova remnant, and was recently recognized as one of the first remnants to have plasma that is overionized. Using SPI we infer the density structure and derive the mass of individual elements in the plasma over the entire remnant. We have compared the abundances inferred with SPI to those obtained from a wide range of supernova explosion models, including both Type Ia and core-collapse, as well as energetic and off-center variants. Type Ia models that incorporate some form of detonation are found to be the most compatible, while pure deflagration models, and all core-collapse models, are found to be incompatible.