Sub-Chandrasekhar mass white dwarfs accreting a helium shell on a carbon-oxygen core are potential progenitors of normal Type Ia supernovae. This work focuses on the details of the onset of the ...carbon detonation in the double detonation sub-Chandrasekhar model. In order to simulate the influence of core-shell mixing on the carbon ignition mechanism, the helium shell and its detonation are followed with an increased resolution compared to the rest of the star treating the propagation of the detonation wave more accurately. This significantly improves the predictions of the nucleosynthetic yields from the helium burning. The simulations were carried out with the A
REPO
code. A carbon-oxygen core with a helium shell was set up in one dimension and mapped to three dimensions. We ensured the stability of the white dwarf with a relaxation step before the hydrodynamic detonation simulation started. Synthetic observables were calculated with the radiative transfer code A
RTIS
. An ignition mechanism of the carbon detonation was observed, which received little attention before. In this “scissors mechanism”, the impact the helium detonation wave has on unburnt material when converging opposite to its ignition spot is strong enough to ignite a carbon detonation. This is possible in a carbon enriched transition region between the core and shell. The detonation mechanism is found to be sensitive to details of the core-shell transition and our models illustrate the need to consider core-shell mixing taking place during the accretion process. Even though the detonation ignition mechanism differs form the converging shock mechanism, the differences in the synthetic observables are not significant. Though they do not fit observations better than previous simulations, they illustrate the need for multi-dimensional simulations.
We revisit the evidence for the contribution of the long-lived radioactive nuclides super(44)Ti, super(55)Fe, super(56)Co, super(57)Co, and super(60)Co to the UVOIR light curve of SN 1987A. We show ...that the V-band luminosity constitutes a roughly constant fraction of the bolometric luminosity between 900 and 1900 days, and we obtain an approximate bolometric light curve out to 4334 days by scaling the late time V-band data by a constant factor where no bolometric light curve data is available. Considering the five most relevant decay chains starting at super(44)Ti, super(55)Co, super(56)Ni, super(57)Ni, and super(60)Co, we perform a least squares fit to the constructed composite bolometric light curve. For the nickel isotopes, we obtain best fit values of M( super(56)Ni) = (7.1 + or - 0.3) x 10 super(-2) M sub(middot in circle) and M( super(57)Ni) = (4.1 + or - 1.8) x 10 super(-3) M sub(middot in circle). Our best fit super(44)Ti mass is M( super(44)Ti) = (0.55 + or - 0.17) x 10 super(-4) M sub(middot in circle), which is in disagreement with the much higher (3.1 + or - 0.8) x 10 super(-4) M sub(middot in circle) recently derived from INTEGRAL observations. The associated uncertainties far exceed the best fit values for super(55)Co and super(60)Co and, as a result, we only give upper limits on the production masses of M( super(55)Co) < 7.2 x 10 super(-3) M sub(middot in circle) and M( super(60)Co) < 1.7 x 10 super(-4) M sub(middot in circle). Furthermore, we find that the leptonic channels in the decay of super(57)Co (internal conversion and Auger electrons) are a significant contribution and constitute up to 15.5% of the total luminosity. Consideration of the kinetic energy of these electrons is essential in lowering our best fit nickel isotope production ratio to super(57)Ni/ super(56)Ni = 2.5 + or - 1.1, which is still somewhat high but is in agreement with gamma-ray observations and model predictions.
Abstract
Manganese abundances are sensitive probes of the progenitors of Type Ia supernovae (SNe Ia). In this work, we present a catalog of manganese abundances in dwarf spheroidal satellites of the ...Milky Way, measured using medium-resolution spectroscopy. Using a simple chemical evolution model, we infer the manganese yield of SNe Ia in the Sculptor dwarf spheroidal galaxy (dSph) and compare to theoretical yields. The sub-solar yield from SNe Ia (
at Fe/ H = −1.5 dex, with negligible dependence on metallicity) implies that sub-Chandrasekhar-mass (sub-
M
Ch
) white dwarf progenitors are the dominant channel of SNe Ia at early times in this galaxy, although some fraction (≳20%) of
M
Ch
Type Ia or Type Iax SNe are still needed to produce the observed yield. First-order corrections for deviations from local thermodynamic equilibrium increase the inferred
by as much as ∼0.3 dex. However, our results also suggest that the nucleosynthetic source of SNe Ia may depend on environment. In particular, we find that dSphs with extended star formation histories (Leo I, Fornax dSphs) appear to have higher Mn/Fe at a given metallicity than galaxies with early bursts of star formation (Sculptor dSph), suggesting that
M
Ch
progenitors may become the dominant channel of SNe Ia at later times in a galaxy’s chemical evolution.
Recent progress in three-dimensional modeling of supernovae (SNe) has shown the importance of asymmetries in the explosion. This calls for a reconsideration of the modeling of the subsequent phase, ...the supernova remnant (SNR), which has commonly relied on simplified ejecta models. In this paper, we bridge SN and SNR studies by using the output of an SN simulation as the input of an SNR simulation carried on for 500 yr. We consider the case of a thermonuclear explosion of a carbon-oxygen white dwarf star as a model for an SN Ia; specifically, we use the N100 delayed detonation model of Seitenzahl et al. In order to analyze the morphology of the SNR, we locate the three discontinuities that delineate the shell of shocked matter: the forward shock, the contact discontinuity, and the reverse shock, and we decompose their radial variations as a function of angular scale and time. Assuming a uniform ambient medium, we find that the impact of the SN on the SNR may still be visible after hundreds of years. Previous 3D simulations aiming to reproduce Tycho's SNR, which started out from spherically symmetric initial conditions, failed to reproduce structures at the largest angular scales observed in X-rays. Our new simulations strongly suggest that the missing ingredient was the initial asymmetries from the SN itself. With this work, we establish a way of assessing the viability of SN models based on the resulting morphology of the SNR.
We investigate whether pure deflagration models of Chandrasekhar-mass carbon–oxygen white dwarf stars can account for one or more subclass of the observed population of Type Ia supernova (SN Ia) ...explosions. We compute a set of 3D full-star hydrodynamic explosion models, in which the deflagration strength is parametrized using the multispot ignition approach. For each model, we calculate detailed nucleosynthesis yields in a post-processing step with a 384 nuclide nuclear network. We also compute synthetic observables with our 3D Monte Carlo radiative transfer code for comparison with observations. For weak and intermediate deflagration strengths (energy release E
nuc ≲ 1.1 × 1051 erg), we find that the explosion leaves behind a bound remnant enriched with 3 to 10 per cent (by mass) of deflagration ashes. However, we do not obtain the large kick velocities recently reported in the literature. We find that weak deflagrations with E
nuc ∼ 0.5 × 1051 erg fit well both the light curves and spectra of 2002cx-like SNe Ia, and models with even lower explosion energies could explain some of the fainter members of this subclass. By comparing our synthetic observables with the properties of SNe Ia, we can exclude the brightest, most vigorously ignited models as candidates for any observed class of SN Ia: their B − V colours deviate significantly from both normal and 2002cx-like SNe Ia and they are too bright to be candidates for other subclasses.
Context. Manganese is predominantly synthesised in Type Ia supernova (SN Ia) explosions. Owing to the entropy dependence of the Mn yield in explosive thermonuclear burning, SNe Ia involving near ...Chandrasekhar-mass (MCh) white dwarfs (WDs) are predicted to produce Mn-to-Fe ratios that significantly exceed those of SN Ia explosions involving sub-Chandrasekhar mass primary WDs. Of all current supernova explosion models, only SN Ia models involving near-MCh WDs produce Mn/Fe ≳ 0.0. Aims. Using the specific yields for competing SN Ia scenarios, we aim to constrain the relative fractions of exploding near-MCh to sub-MCh primary WDs in the Galaxy. Methods. We extract the Mn yields from three-dimensional thermonuclear supernova simulations that refer to different initial setups and progenitor channels. We then compute the chemical evolution of Mn in the solar neighborhood, assuming SNe Ia are made up of different relative fractions of the considered explosion models. Results. We find that due to the entropy dependence of freeze-out yields from nuclear statistical equilibrium, Mn/Fe depends strongly on the mass of the exploding WD, with near-MCh WDs producing substantially higher Mn/Fe than sub-MCh WDs. Of all nucleosynthetic sources potentially influencing the chemical evolution of Mn, only explosion models involving the thermonuclear incineration of near-MCh WDs predict solar or super-solar Mn/Fe. Consequently, we find in our chemical evolution calculations that the observed Mn/Fe in the solar neighborhood at Fe/H ≳ 0.0 cannot be reproduced without near-MCh SN Ia primaries. Assuming that 50% of all SNe Ia stem from explosive thermonuclear burning in near-MCh WDs results in a good match to data.
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.
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-Chandrasekhar-mass 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 (2563 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 (5123 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 106 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 56Ni and stable Fe. We therefore do not find good agreement of the model with SN 1991T.
Using integral field data we extract the optical spectra of shocked interstellar clouds in Kepler's supernova remnant located in the inner regions of our Galaxy, as well as in the Large Magellanic ...Cloud, the Small Magellanic Cloud, NGC 6822, and IC 1613. Using self-consistent shock modeling, we make a new determination of the chemical composition of the interstellar medium in N, O, Ne, S, Cl, and Ar in these galaxies and obtain accurate estimates of the fraction of refractory grains destroyed in the shock. By comparing our derived abundances with those obtained in recent works using observations of B-stars, F supergiant stars, and H ii regions, we provide a new calibration for abundance scaling in the range of .
We present results for a suite of 14 three-dimensional, high-resolution hydrodynamical simulations of delayed-detonation models of Type Ia supernova (SN Ia) explosions. This model suite comprises the ...first set of three-dimensional SN Ia simulations with detailed isotopic yield information. As such, it may serve as a data base for Chandrasekhar-mass delayed-detonation model nucleosynthetic yields and for deriving synthetic observables such as spectra and light curves. We employ a physically motivated, stochastic model based on turbulent velocity fluctuations and fuel density to calculate in situ the deflagration-to-detonation transition probabilities. To obtain different strengths of the deflagration phase and thereby different degrees of pre-expansion, we have chosen a sequence of initial models with 1, 3, 5, 10, 20, 40, 100, 150, 200, 300 and 1600 (two different realizations) ignition kernels in a hydrostatic white dwarf with a central density of 2.9 × 109 g cm−3, as well as one high central density (5.5 × 109 g cm−3) and one low central density (1.0 × 109 g cm−3) rendition of the 100 ignition kernel configuration. For each simulation, we determined detailed nucleosynthetic yields by post-processing 106 tracer particles with a 384 nuclide reaction network. All delayed-detonation models result in explosions unbinding the white dwarf, producing a range of 56Ni masses from 0.32 to 1.11 M. As a general trend, the models predict that the stable neutron-rich iron-group isotopes are not found at the lowest velocities, but rather at intermediate velocities (∼3000-10 000 km s−1) in a shell surrounding a 56Ni-rich core. The models further predict relatively low-velocity oxygen and carbon, with typical minimum velocities around 4000 and 10 000 km s−1, respectively.
PDF
