THE IMPACT OF TYPE Ia SUPERNOVA EXPLOSIONS ON HELIUM COMPANIONS IN THE CHANDRASEKHAR-MASS EXPLOSION SCENARIO (original) (raw)
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The response of a helium white dwarf to an exploding Type Ia supernova
Monthly Notices of the Royal Astronomical Society, 2015
We conduct numerical simulations of the interacting ejecta from an exploding CO white dwarf (WD) with the He WD donor in the double-detonation scenario for Type Ia supernovae (SNe Ia), and find that the descendant supernova remnant (SNR) is highly asymmetrical, in contradiction with observations. When the donor He WD has low mass, M WD = 0.2M ⊙ , it is at a distance of ∼ 0.08R ⊙ from the explosion, and helium is not ignited. The low mass He WD casts an 'ejecta shadow' behind it, that has imprint in the SN remnant (SNR) hundreds of years later. The outer parts of the shadowed side are fainter and its boundary with the ambient gas is somewhat flat. These features are not found in known SNRs. More massive He WD donors, M WD ≃ 0.4M ⊙ , must be closer to the CO WD to transfer mass. At a distance a 0.045R ⊙ helium is ignited and the He WD explodes. This explosion leads to a highly asymmetrical SNR and to ejection of ∼ 0.15M ⊙ of helium, both of which contradict observations of SNe Ia.
Sub-Chandrasekhar Mass Models for Supernovae
The Astrophysical Journal, 2011
For carbon-oxygen white dwarfs accreting hydrogen or helium at rates in the range ∼ 1-10 ×10 −8 M ⊙ y −1 , a variety of explosive outcomes is possible well before the star reaches the Chandrasekhar mass. These outcomes are surveyed for a range of white dwarf masses (0.7-1.1 M ⊙), accretion rates (1 − 7 × 10 −8 M ⊙ y −1), and initial white dwarf temperatures (0.01 and 1 L ⊙). The results are particularly sensitive to the convection that goes on during the last few minutes before the explosion. Unless this convection maintains a shallow temperature gradient, and unless the density is sufficiently high, the accreted helium does not detonate. Below a critical helium ignition density, which we estimate to be 5 − 10 × 10 5 g cm −3 , either helium novae or helium deflagrations result. The hydrodynamics, nucleosynthesis, light curves, and spectra of a representative sample of detonating and deflagrating models are explored. Some can be quite faint indeed, powered at peak for a few days by the decay of 48 Cr and 48 V. Only the hottest, most massive white dwarfs considered with the smallest helium layers, show reasonable agreement with the light curves and spectra of common Type Ia supernovae. For the other models, especially those involving lighter white dwarfs, the helium shell mass exceeds 0.05 M ⊙ and the mass of the 56 Ni that is synthesized exceeds 0.01 M ⊙. These explosions do not look like ordinary Type Ia supernovae, or any other frequently observed transient.
Sub-Chandrasekhar mass models for Type IA supernovae
The Astrophysical Journal, 1994
For carbon-oxygen white dwarfs accreting hydrogen or helium at rates in the range ∼ 1-10 ×10 −8 M ⊙ y −1 , a variety of explosive outcomes is possible well before the star reaches the Chandrasekhar mass. These outcomes are surveyed for a range of white dwarf masses (0.7-1.1 M ⊙), accretion rates (1 − 7 × 10 −8 M ⊙ y −1), and initial white dwarf temperatures (0.01 and 1 L ⊙). The results are particularly sensitive to the convection that goes on during the last few minutes before the explosion. Unless this convection maintains a shallow temperature gradient, and unless the density is sufficiently high, the accreted helium does not detonate. Below a critical helium ignition density, which we estimate to be 5 − 10 × 10 5 g cm −3 , either helium novae or helium deflagrations result. The hydrodynamics, nucleosynthesis, light curves, and spectra of a representative sample of detonating and deflagrating models are explored. Some can be quite faint indeed, powered at peak for a few days by the decay of 48 Cr and 48 V. Only the hottest, most massive white dwarfs considered with the smallest helium layers, show reasonable agreement with the light curves and spectra of common Type Ia supernovae. For the other models, especially those involving lighter white dwarfs, the helium shell mass exceeds 0.05 M ⊙ and the mass of the 56 Ni that is synthesized exceeds 0.01 M ⊙. These explosions do not look like ordinary Type Ia supernovae, or any other frequently observed transient.
Astronomy & Astrophysics, 2012
Context. The identity of the progenitor systems of Type Ia supernovae (SNe Ia) is still uncertain. In the single-degenerate scenario, the interaction between the supernova blast wave and the outer layers of a main sequence companion star strips off hydrogen-rich material which is then mixed into the ejecta. Strong contamination of the supernova ejecta with stripped material could lead to a conflict with observations of SNe Ia. This constrains the single-degenerate progenitor model. Aims. In this work, our previous simulations based on simplified progenitor donor stars have been updated by adopting more realistic progenitor-system models that result from fully detailed, state-of-the-art binary evolution calculations. Methods. We use Eggleton's stellar evolution code including the optically thick accretion wind model and taking into account the possibility of the effects of accretion disk instabilities to obtain realistic models of companion stars for different progenitor systems. The impact of the supernova blast wave on these companion stars is followed in three-dimensional hydrodynamic simulations employing the smoothed particle hydrodynamics (SPH) code GADGET3. Results. For a suite of main sequence companions, we find that the mass of the material stripped from the companions range from 0.11 M ⊙ to 0.18 M ⊙ . The kick velocity delivered by the impact is between 51 km s −1 and 105 km s −1 . We find that the stripped mass and kick velocity depend on the ratio of the orbital separation to the radius of a companion, a f /R. They can be fitted in good approximation by a power law for a given companion model. However, we do not find a single power law relation holding for different companion models. This implies that the structure of the companion star is also important for the amount of stripped material. Conclusions. With more realistic companion star models than those employed in previous studies, our simulations show that the hydrogen masses stripped from companions are inconsistent with the best observational limits ( 0.01M ⊙ ) derived from SN Ia nebular spectra. However, a rigorous forward modeling from the results of impact simulations with radiation transfer is required to reliably predict observable signatures of the stripped hydrogen and to conclusively assess the viability of the considered SN Ia progenitor scenario.
IMPACT OF TYPE Ia SUPERNOVA EJECTA ON BINARY COMPANIONS IN THE SINGLE-DEGENERATE SCENARIO
The Astrophysical Journal, 2012
Type Ia supernovae are thought to be caused by thermonuclear explosions of a carbon-oxygen white dwarf in close binary systems. In the single-degenerate scenario (SDS), the companion star is non-degenerate and can be significantly affected by the explosion. We explore this interaction by means of multi-dimensional adaptive mesh refinement simulations using the FLASH code. We consider several different companion types, including main-sequence-like stars (MS), red giants (RG), and helium stars (He). In addition, we include the symmetry-breaking effects of orbital motion, rotation of the non-degenerate star, and Roche-lobe overflow. A detailed study of a sub-grid model for Type Ia supernovae is also presented. We find that the dependence of the unbound stellar mass and kick velocity on the initial binary separation can be fitted by power-law relations. By using the tracer particles in FLASH, the process leading to the unbinding of matter is dominated by ablation, which has usually been neglected in past analytical studies. The level of Ni/Fe contamination of the companion that results from the passage of the supernova ejecta is found to be a ∼ 10 −5 M ⊙ for the MS star, ∼ 10 −4 M ⊙ for the He star, and ∼ 10 −8 M ⊙ for the RG. The spinning MS companion star loses about half of its initial angular momentum during the impact, causing the rotational velocity to drop to a quarter of the original rotational velocity, suggesting that the Tycho G star is a promising progenitor candidate in the SDS.
Supernovae from Direct Collisions of White Dwarfs and the Role of Helium Shell Ignition
The Astrophysical Journal, 2016
Models for supernovae (SNe) arising from thermonuclear explosions of white dwarfs (WDs) have been extensively studied over the last few decades, mostly focusing on the single degenerate (accretion of material of a WD) and double degenerate (WD-WD merger) scenarios. In recent years it was suggested that WD-WD direct collisions provide an additional channel for such explosions. Here we extend the studies of such explosions, and explore the role of Helium-shells in affecting the thermonuclear explosions. We study both the impact of low-mass helium (∼ 0.01 M ⊙) shells, as well as high mass shells (≥ 0.1 M ⊙). We find that detonation of the massive helium layers precede the detonation of the WD Carbon-Oxygen (CO) bulk during the collision and can change the explosive evolution and outcomes for the cases of high mass He-shells. In particular, the He-shell detonation propagates on the WD surface and inefficiently burns material prior to the CO detonation that later follows in the central parts of the WD. Such evolution leads to larger production of intermediate elements, producing larger yields of 44 Ti and 48 Cr relative to the pure CO-CO WD collisions. Collisions of WDs with a low-mass He-shell do not give rise to helium detonation, but helium burning does precede the CO bulk detonation. Such collisions produce a high velocity, low-mass of ejected burned material enriched with intermediate elements, with smaller changes to the overall explosion outcomes. The various effects arising from the contribution of low/high mass He layers change the kinematics and the morphological structure of collision-induced SNe and may thereby provide unique observational signatures for such SNe, and play a role in the chemical enrichment of galaxies and the production of intermediate elements and positrons from their longer-term decay.
Hydrodynamic Simulations of Classical Novae: Accretion onto CO White Dwarfs as SN Ia Progenitors
Proceedings of The Golden Age of Cataclysmic Variables and Related Objects IV — PoS(GOLDEN 2017), 2018
We report on our continuing studies of Classical Nova explosions by following the evolution of thermonuclear runaways (TNRs) on carbon-oxygen (CO) white dwarfs (WDs). We have varied both the mass of the WD and the composition of the accreted material. Rather than assuming that the material has mixed from the beginning, we now rely on the results of the multidimensional (multi-D) studies of mixing as a consequence of the TNRs in WDs that accreted only Solar matter. The multi-D studies find that mixing with the core occurs after the TNR is well underway and reach enrichment levels in agreement with observations of the ejecta abundances. We report on 3 studies in this paper. First, simulations in which we accrete only Solar matter with NOVA (our 1-D, fully implicit, hydro code). Second, we use MESA for similar studies in which we accrete only Solar material and compare the results. Third, we accrete Solar matter until the TNR is initiated and then switch the composition in the accreted layers to a mixed composition: either 25% core and 75% Solar or 50% core and 50% Solar. The amount of accreted material is inversely proportional to the initial 12 C abundance. Thus, accreting Solar material results in more material to fuel the outburst-much larger than in the earlier studies where mixed materials were used from the beginning. We tabulate the amount of ejected gases, their velocities, and abundances. We predict the amount of 7 Li and 7 Be produced and ejected by the explosion and compare our predictions to our Large Binocular Telescope (LBT) high dispersion spectra which determined the abundance of 7 Li in nova V5668 Sgr. Finally, many of these simulations eject significantly less mass than accreted and, therefore, the WD is growing in mass toward the Chandrasekhar Limit.
Monthly Notices of the Royal Astronomical Society, 2021
Normal type Ia supernovae (SNe) are thought to arise from the thermonuclear explosion of massive (>0.8 M⊙) carbon–oxygen white dwarfs (WDs), although the exact mechanism is debated. In some models, helium accretion on to a carbon–oxygen (CO) WD from a companion was suggested to dynamically trigger a detonation of the accreted helium shell. The helium detonation then produces a shock that after converging on itself close to the core of the CO WD, triggers a secondary carbon detonation, and gives rise to an energetic explosion. However, most studies of such scenarios have been done in one or two dimensions, and/or did not consider self-consistent models for the accretion and the He donor. Here, we make use of detailed 3D simulation to study the interaction of a He-rich hybrid 0.69,mathrmModot0.69\, \mathrm{M_\odot }0.69,mathrmModot HeCO WD with a more massive 0.8,mathrmModot0.8\, \mathrm{M_\odot }0.8,mathrmModot CO WD. We find that accretion from the hybrid WD on to the CO WD gives rise to a helium detonation. However, the helium detonati...
Monthly Notices of the Royal Astronomical Society
Extremely luminous, super-Chandrasekhar (SC) Type Ia Supernovae (SNe Ia) are as yet an unexplained phenomenon. We analyse a well-observed SN of this class, SN 2009dc, by modelling its photospheric spectra with a spectral synthesis code, using the technique of 'Abundance Tomography'. We present spectral models based on different density profiles, corresponding to different explosion scenarios, and discuss their consistency. First, we use a density structure of a simulated explosion of a 2 M_sun rotating C-O white dwarf (WD), which is often proposed as a possibility to explain SC SNe Ia. Then, we test a density profile empirically inferred from the evolution of line velocities (blueshifts). This model may be interpreted as a core-collapse SN with an ejecta mass ~ 3 M_sun. Finally, we calculate spectra assuming an interaction scenario. In such a scenario, SN 2009dc would be a standard WD explosion with a normal intrinsic luminosity, and this luminosity would be augmented by int...
Single point off-center helium ignitions as origin of some Type Ia supernovae
International Symposium on …, 2006
The explosion of a helium layer accreted on top of a white dwarf, leading to the subsequent explosion of the star (while the accreting dwarf is still below the Chandrasekhar mass limit) is an alternative model for some subluminous Type Ia supernovae explosions. In this communication we present two preliminary hydrodynamical simulations concerning these socalled Sub-Chandrasekhar mass models for Type Ia supernovae, calculated in two dimensions. In the first calculation we have assumed one single detonation travelling through the helium layer which, after a while, induces the detonation of the carbon layer at the antipodes of the original ignition point. In the second case we assumed the prompt detonation of the carbon just beneath the ignition point. A comparison between these two models is presented.