White dwarf mergers and the origin of R coronae borealis stars - Lorén Aguilar, Pablo; Longland, Richard Leigh; José Pont, Jordi; García-Berro Montilla, Enrique; Althaus, Leandro G.; Isern-Fontanet, J.
We present a nucleosynthesis study of the merger of a 0.4 M⊙ helium white dwarf with a 0.8 M⊙ carbon-oxygen white dwarf, coupling the thermodynamic history of Smoothed Particle Hydrodynamics particles with a post-processing code.
The resulting chemical abundance pattern, particularly for oxygen and fluorine, is in
qualitative agreement with the observed abundances in R Coronae Borealis stars.
Interaction of Supernovae remnants: From the circumstellar medium to the terrestrial laboratory - Velarde, P; García Senz, Domingo; Bravo Guil, Eduardo; Ogando, F; Relaño, A; Oliva, E
The evolution of supernova remnants (SNRs) represents a useful and natural laboratory for gasdynamics studies. In this paper the results of several hydrodynamical simulations of the propagation and early phases of interaction of two SNRs embedded in a homogeneous interstellar environment are shown. In particular, the hydrodynamic evolution and collision of twin SNRs during their self-similar stage has been simulated using a two-dimensional Lagrangian hydrocode. In addition, the results of a detailed simulation that attempts to set the adequate conditions to reproduce the same phenomenon through laser ablation of two plastic plugs at the laboratory scale are presented. These results...
Production of intermediate-mass and heavy nuclei - Thielemann, F. K.; Frölich, Carla; Hirschi, R.; Liebendörfer, M.; Dillmann, I.; Mocelj, D.; Rauscher, t.; Martínez Pinedo, Gabriel; Langanke, K; Farouqi, K; Kratz, K.L.; Pfeiffer, B.; Panov, I.; Nadyozhin, D.K.; Blinnikov, S.; Bravo Guil, Eduardo; Hix, W.R.; Höflich, P.; Zinner, Ernst
Unified one-dimensional simulations of gamma-ray line emission from type Ia supernovae - Milne, P A; Hungerford, A L; Fryer, C L; Evans, T M; Urbatsch, T J; Boggs, S E; Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Hirschmann, A; Kumagai, S; Pinto, P A; The, L S
The light curves of Type Ia supernovae (SNe Ia) are powered by gamma rays emitted by the decay of radioactive elements such as 56Ni and its decay products. These gamma rays are downscattered, absorbed, and eventually reprocessed into the optical emission that makes up the bulk of all SN observations. Detection of the gamma rays that escape the expanding star provide the only direct means to study this power source for SN Ia light curves. Unfortunately, disagreements between calculations for the gamma-ray lines have made it difficult to interpret any gamma-ray observations. Here we present a detailed comparison of the...
Bounds on the possible evolution of the gravitational constant from cosmological type-Ia supernovae - Gaztañaga, E; García-Berro Montilla, Enrique; Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Domínguez, I
Recent high-redshift type-Ia supernovae results can be used to set new bounds on a possible variation of the gravitational constant G. If the local value of G at the space-time location of distant supernovae is different, it would change both the kinetic energy release and the amount of 56Ni synthesized in the supernova outburst. Both effects are related to a change in the Chandrasekhar mass MCh∝G-3/2. In addition, the integrated variation of G with time would also affect the cosmic evolution and therefore the luminosity distance relation. We show that the later effect in the magnitudes of type-Ia supernovae is...
SIXE: A Payload for MINISAT-02 - Gómez, J; Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Giovannelli, F; Padula, C L
A description of the X-ray instrument SIXE proposed for the MINISAT-02 mission is presented. The description includes the scientific goals and instrument performances.
A particle code for deflagrations in white dwarfs. I. Numerical techniques - García Senz, Domingo; Bravo Guil, Eduardo; Serichol Augué, Núria
In this paper we report some specific features of the numerical technique used to study the dynamic evolution of massive white dwarfs following the explosive ignition of nuclear fuel under degenerate conditions. We focus on three important points: (1) how to construct a stable initial model for white dwarfs with a central density ρc > 109 g cm-3 in the context of smoothed particle hydrodynamics (SPH); (2) the procedure devised in the numerical handling of combustion fronts and thermal discontinuities; and (3) a proposed method based on techniques of analysis of dynamic sets of points to characterize the flame front...
Constraining deflagration models of type Ia supernovae through intermediate-mass elements - García Senz, Domingo; Bravo Guil, Eduardo; Cabezón Gómez, Rubén Martín; Woosley, S E
The physical structure of a nuclear flame is a basic ingredient of the theory of Type Ia supernovae (SNe Ia). Assuming an exponential density reduction with several characteristic times, we have followed the evolution of a planar nuclear flame in an expanding background from an initial density of 6.6 × 107 g cm-3 down to 2 × 106 g cm-3. The total amount of synthesized intermediate-mass elements (IMEs), from silicon to calcium, was monitored during the calculation. We have used the computed mass fractions, XIME, of these elements to estimate the total amount of IMEs synthesized during the deflagration of...
Neutrino-induced nucleosynthesis of a > 64 nuclei: The vp process - Fröhlich, C; Martínez, G; Liebendörfer, M; Thielemann, F -K; Bravo Guil, Eduardo; Hix, W R; Langanke, K; Zinner, N T
We present a new nucleosynthesis process that we denote as the νp process, which occurs in supernovae (and possibly gamma-ray bursts) when strong neutrino fluxes create proton-rich ejecta. In this process, antineutrino absorptions in the proton-rich environment produce neutrons that are immediately captured by neutron-deficient nuclei. This allows for the nucleosynthesis of nuclei with mass numbers A>64, making this process a possible candidate to explain the origin of the solar abundances of 92,94Mo and 96,98Ru. This process also offers a natural explanation for the large abundance of Sr seen in a hyper-metal-poor star.
Composition of the innermost core-collapse supernova ejecta - Fröhlich, C; Hauser, P; Liebendörfer, M; Martínez, G; Thielemann, F -K; Bravo Guil, Eduardo; Zinner, N T; Hix, W R; Langanke, K; Mezzacappa, A; Nomoto, K
With currently known input physics and computer simulations in one dimension, a self-consistent treatment of core-collapse supernovae does not yet lead to successful explosions, while two-dimensional models show some promise. Thus, there are strong indications that the delayed neutrino mechanism works combined with a multidimensional convection treatment for unstable layers (possibly with the aid of rotation, magnetic fields and/or still existent uncertainties in neutrino opacities). On the other hand, there is a need to provide correct nucleosynthesis abundances for the progressing field of galactic evolution and observations of low-metallicity stars. The innermost ejecta is directly affected by the explosion mechanism,...
Exploring the physics of type Ia supernovae through the x-ray spectra of their remnants - Badenes, C; Borkowski, K; Bravo Guil, Eduardo; Hughes, J P; Hwang, U
We present the results of an ongoing project to use the X-ray observations of Type Ia Supernova Remnants to constrain the physical processes involved in Type Ia Supernova explosions. We use the Tycho Supernova Remnant (SN 1572) as a benchmark case, comparing its observed spectrum with models for the X-ray emission from the shocked ejecta generated from di erent kinds of Type Ia explosions. Both the integrated spectrum of Tycho and the spatial distribution of the Fe and Si emission in the remnant are well reproduced by delayed detonation models with stratiﬁed ejecta. All the other Type Ia explosion models...
Sph simulations of deflagrations in supernovae - Bravo Guil, Eduardo; García Senz, Domingo
Some results of a set of tridimensional calculations concerning the explosion of a white dwarf by means of a smooth particle hydrodynamics (SPH) code are presented. The burning front advance is solved along with the hydrodynamics of the whole star, and a characterization of the front surface in terms of fractal concepts is done. Our main result indicates that the surface of the deflagration front sought at the largest scales of the Rayleigh-Taylor instability can be characterized as a fractal with a time-dependent dimension, D(t), whose value is 2 ≤ D(t) ≤ 2.4.
Nucleosynthesis as a result of multiple delayed detonations in Type Ia Supernovae - García Senz, Domingo; Bravo Guil, Eduardo
The explosion of a white dwarf of mass 1.36 M⊙ has been simulated in three dimensions with the aid of a SPH code. The explosion follows the delayed detonation paradigm. In this case the deflagration-detonation transition is induced by the large corrugation of the flame front resulting from Rayleigh-Taylor instability and turbulence. The nucleosynthetic yields have been calculated, showing that some neutronized isotopes such as 54Fe or 58Ni are not overproduced with respect to the solar system ratios. The distribution of intermediate-mass elements is also compatible with the spectra of normal SNIa. The exception is, however, the abundance of carbon...