Mostrando recursos 101 - 120 de 194

  1. The imprint of presupernova evolution on supernova remnants

    Badenes Montoliu, Carles; Bravo Guil, Eduardo
    The evolution of Type Ia supernova binary system progenitors is highly uncertain. Several evolutionary models predict that the accretion of mass onto the white dwarf is accompanied by mass ejection from the binary in the form of a powerful wind, but very few observations have been made during the initial phase of formation of supernova remnants, when the interaction of supernova ejecta with presupernova wind could be tested. Here we present hydrodynamical simulations of supernova ejecta interaction with an ambient medium modified by presupernova wind. The structure of the ambient medium when the supernova explodes is very sensitive to the...

  2. Thermal X-ray emission from shocked ejecta in Type Ia supernova remnants. II. Parameters affecting the spectrum

    Badenes Montoliu, Carles; Borkowski, K.J.; Bravo Guil, Eduardo
    The supernova remnants (SNRs) left behind by Type Ia supernovae (SNe) provide an excellent opportunity for the study of these enigmatic objects. In a previous work we showed that it is possible to use the X-ray spectra of young Type Ia SNRs to explore the physics of Type Ia SNe and identify the relevant mechanism underlying these explosions. Our simulation technique is based on hydrodynamic and nonequilibrium ionization calculations of the interaction of a grid of Type Ia explosion models with the surrounding ambient medium, coupled to an X-ray spectral code. In this work we explore the influence of two...

  3. Thermal X-ray emission from shocked ejecta in Type Ia supernova remnants: Prospects for explosion mechanism identification

    Badenes Montoliu, Carles; Bravo Guil, Eduardo; Borkowski, K.J.; Domínguez, Inmaculada
    The explosion mechanism behind Type Ia supernovae is a matter of continuing debate. The diverse attempts to identify or at least constrain the physical processes involved in the explosion have been only partially successful so far. In this paper we propose to use the thermal X-ray emission from young supernova remnants (SNRs) originating in Type Ia events to extract relevant information concerning the explosions themselves. We have produced a grid of thermonuclear supernova models representative of the paradigms currently under debate: pure deflagrations, delayed detonations, pulsating delayed detonations, and sub-Chandrasekhar explosions, using their density and chemical composition profiles to simulate...

  4. The persistence of memory, or how the X-ray spectrum of SNR 0509-67.5 reveals the brightness of its parent Type Ia supernova

    Badenes Montoliu, Carles; Hughes, J.P.; Cassam, G.; Bravo Guil, Eduardo
    We examine the dynamics and X-ray spectrum of the young Type Ia supernova remnant 0509–67.5 in the context of the recent results obtained from the optical spectroscopy of its light echo. Our goal is to estimate the kinetic energy of the supernova explosion using Chandra and XMM-Newton observations of the supernova remnant, thus placing the birth event of 0509–67.5 in the sequence of dim-to-bright Type Ia supernovae. We base our analysis on a standard grid of one-dimensional delayed detonation explosion models, together with hydrodynamic and X-ray spectral calculations of the supernova remnant evolution. From the remnant dynamics and the properties...

  5. Constraints on the physics of type Ia supernovae from the X-ray spectrum of the Tycho supernova remnant

    Badenes Montoliu, Carles; Borkowski, K.J.; Hughes, J.P.; Hwang, U.; Bravo Guil, Eduardo
    We explore the relationship between the models for progenitor systems of Type Ia supernovae and the properties of the supernova remnants that evolve after the explosion. Most models for Type Ia progenitors in the single-degenerate scenario predict substantial outflows during the presupernova evolution. Expanding on previous work, we estimate the imprint of these outflows on the structure of the circumstellar medium at the time of the supernova explosion, and the effect that this modified circumstellar medium has on the evolution of the ensuing supernova remnant. We compare our simulations with the observational properties of known Type Ia supernova remnants in...

  6. Are the models for type Ia supernova progenitors consistent with the properties of supernova remnants?

    Badenes Montoliu, Carles; Hughes, J.P.; Bravo Guil, Eduardo; Langer, N.
    We explore the relationship between the models for progenitor systems of Type Ia supernovae and the properties of the supernova remnants that evolve after the explosion. Most models for Type Ia progenitors in the single-degenerate scenario predict substantial outflows during the presupernova evolution. Expanding on previous work, we estimate the imprint of these outflows on the structure of the circumstellar medium at the time of the supernova explosion, and the effect that this modified circumstellar medium has on the evolution of the ensuing supernova remnant. We compare our simulations with the observational properties of known Type Ia supernova remnants in...

  7. The science of y-ray spectroscopy

    Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Hirschmann, Alina
    The explosion mechanism associated with thermonuclear supernovae (SNIa) is still a matter of debate. Nevertheless, there is a wide agreement that high amounts of radioactive nuclei are produced during these events, that are expected to be strong γ-ray emitters. In this paper we investigate the use of γ-rays as a diagnostic tool. For this purpose we have performed a complete study of the γ-ray spectra associated with all the different scenarios currently proposed: detonation, deflagration, delayed detonation, pulsating delayed detonation and off-center detonation. Our study shows that the γ-ray emission from SNIa is, effectively, a promising tool but that must...

  8. P-process nucleosynthesis in detonating white dwarfs in the light of multidimensional hydrodynamical models

    Goriely, S; García Senz, Domingo; Bravo Guil, Eduardo; José Pont, Jordi
    The p-process nucleosynthesis in He-accreting white dwarfs with sub-Chandrasekhar mass is revisited in the light of multi-dimensional hydrodynamical simulations. Post-processing calculations are performed on a sample of well-chosen track particles representative of the core and envelope material that is subject to the p-process. The p-abundance distributions in the disrupted core as well as in the ejected envelope are estimated and compared with previous analysis based on spherical-symmetric simulations. The present calculations confirm the results obtained in 1D simulations and the possibility to produce in particular the puzzling Mo and Ru p-isotopes in the envelope, provided it is initially enriched in...

  9. A model grid for the spectral analysis of X-ray emission in young Type Ia supernova remnants

    Badenes Montoliu, Carles; Bravo Guil, Eduardo; Borkowski, K.J.
    We address a new set of models for the spectral analysis of the X-ray emission from young, ejecta-dominated Type Ia supernova remnants. These models are based on hydrodynamic simulations of the interaction between Type Ia supernova explosion models and the surrounding ambient medium, coupled to self-consistent ionization and electron heating calculations in the shocked supernova ejecta, and the generation of synthetic spectra with an appropriate spectral code. The details are provided elsewhere, but in this paper we concentrate on a specific class of Type Ia explosion models (delayed detonations), commenting on the differences that arise between their synthetic X-ray spectra...

  10. Hypersonic collision of a blast wave on a low-mass star

    García Senz, Domingo; Serichol Augué, Núria; Bravo Guil, Eduardo
    When a neutron star is born as a result of the accretion-induced collapse (AIC) of a white dwarf, a small but signi_cant fraction of its mass can be simultaneously expelled at a velocity of around 104 kms −1. In this paper we study the collision between the gas ejected during the AIC of a white dwarf and a 0.3 M_ mainsequence star by using numerical simulation techniques. We found that, for a plausible combination of the orbital parameters and impact energy, the low-mass star is completely destroyed. This scenario can help to explain the origin of isolated millisecond pulsars.

  11. Type Ia Supernova models arising from different distributions of igniting points

    García Senz, Domingo; Bravo Guil, Eduardo
    In this paper we address the theory of type Ia supernovae from the moment of carbon runaway up to several hours after the explosion. We have concentrated on the boiling-pot model: a deflagration characterized by the (nearly-) simultaneous ignition of a number of bubbles that pervade the core of the white dwarf.

  12. Coulomb corrections to the equation of state of nuclear statistical equilibrium matter: implications for SNIa nucleosynthesis and the accretion-induced collapse of white dwarfs

    Bravo Guil, Eduardo; García Senz, Domingo
    Coulomb corrections to the equation of state of degenerate matter are usually neglected in high-temperature regimes, owing to the inverse dependence of the plasma coupling constant, G, on temperature. However, nuclear statistical equilibrium matter is characterized by a large abundance by mass of large-Z (iron group) nuclei. It is found that Coulomb corrections to the ion ideal gas equation of state of matter in nuclear statistical equilibrium are important at temperatures T≲5–10×109 K and densities ρ≳108 g cm−3. At a temperature T=8.5×109 K and a density ρ=8×109 g cm−3, the neutronization rate is larger by ≳28 per cent when Coulomb...

  13. The fate of CO white dwarfs that experience slow deflagrations

    Bravo Guil, Eduardo; Domínguez, Inmaculada; Isern Vilaboy, Jordi
    It has been suggested that the differences among the observational Type Ia supernovae (SNIa) set can be accounted for by invoking two regimes of propagation of combustion. Normal SNIa should be produced by rapid deflagrations that rapidly propagate across a white dwarf, while dim SNIa should be a consequence of a detonation issued during the contraction phase of a pulsation induced by a very slow conductive deflagration. In this paper, we explore the observational consequences of deflagrations, the properties of which are in between both behaviours. Using different laws for the flame velocity as a function of flame radius, a...

  14. Production of short-lived radioactive nuclei in Super Asymptotic Giant Branch stars

    Doherty, Carolyn L.; Lugaro, M.; Lau, H. H. B.; Siess, Lionel; Lattanzio, John; Gil Pons, Pilar

  15. Narcís Monturiol i la seva Idea General del Universo (1874)

    Roca Rosell, Antoni Maria Claret
    En els darrers anys de la seva vida, Narcís Monturiol actuà com a dirigent republicà, no solament participant en la formació de noves organitzacions, sinó també en la tasca de difondre una ideologia progressista. En la conferència que analitzem en aquest article, Monturiol oferí la perspectiva de què es disposava a la seva època sobre la constitució de l’Univers. Com ell mateix va dir, es tractava de fer veure que la ciència era una de les principals eines de transformació social.

  16. Neutron capture cross section of unstable 63-Ni: implications for stellar nucleosynthesis

    Lederer, C.; Massimi, C.; Calviño Tavares, Francisco; Cortés Rossell, Guillem Pere; Gómez Hornillos, María Belén
    The 63Ni(n,γ) cross section has been measured for the first time at the neutron time-of-flight facility n_TOF at CERN from thermal neutron energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian averaged cross sections were calculated for thermal energies from   kT=5–100  keV with uncertainties around 20%. Stellar model calculations for a 25M⊙ star show that the new data have a significant effect on the s-process production of 63Cu, 64Ni, and 64Zn in massive stars, allowing stronger constraints on the Cu yields from explosive nucleosynthesis in the subsequent supernova.

  17. Production of short-lived radioactive nuclei in super asymptotic giant branch star

    Doherty, Carolyn L.; Lugaro, M.; Lau, H.; Siess, Lionel; Lattanzio, John; Gil Pons, Pilar

  18. The upper-mass limit for the formation of super-agb stars and the dredge-out phenomenon

    Gil Pons, Pilar; Doherty, Carolyn L.
    We have computed the evolution of Super-AGB stars from the main sequence and up to a few hundred thermal pulses, with special attention to the low metallicity cases (Z = 10 10; 10 5; 10 4 and 10 3). Our computations have been performed using time– dependent mixing and new opacity tables that admit variations in the abundances of carbon and oxygen. By following the evolution along the main central burning stages and the early TP-SAGB, we resolve the upper mass limits for the formation of TP-SAGB stars and determine the mass range at which the dredge-out phenomenon occurs. This phenomenon involves the merger of a convective...

  19. On the fate of extremely low metallicity stars

    Gil Pons, Pilar; Gutierrez Cabello, Jorge Luis; García-Berro Montilla, Enrique; Althaus, Leandro Gabriel
    We have computed and analyzed the evolution of intermediate-mass stars of metallicity Z = 10−5 from the main sequence until the early stages of the TP-(S)AGB phase. In order to check the influence of mixing we have performed our calculations using two different evolutionary codes, EVOLVE — which does not include diffusion but allows for overshooting— and LPCODE, which includes diffusion and overshooting “à-la-Herwig”. Important differences appear during the TP– AGB phase, as the calculations done with EVOLVE lead to an almost negligible third dredge-up, whereas the sequences computed with LPCODE show important third dredge-up and, therefore, significant enrichment in metals of the envelope. This fact has...

  20. Testing the concept of integral approach to derivatives within the smoothed particle hydrodynamics technique in astrophysical scenarios

    Cabezón Gómez, Rubén Martín; García Senz, Domingo; Escartín Vigo, José Antonio
    Context. The smoothed particle hydrodynamics (SPH) technique is a well-known numerical method that has been applied to simulating the evolution of a wide variety of systems. Modern astrophysical applications of the method rely on the Lagrangian formulation of fluid Euler equations, which is fully conservative. A different scheme, based on a matrix approach to the SPH equations is currently being used in computational fluid dynamics. An original matrix formulation of SPH based on an integral approach to the derivatives, called IAD0, has been recently proposed and is fully conservative and well-suited to simulating astrophysical processes. Aims. The behavior of the IAD0...

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