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  • Observation of SN2011fe with INTEGRAL - I : pre-maximum phase

     Isern Vilaboy, Jordi; Jean, Pierre; Bravo Guil, Eduardo; Diehl, Roland; Knödlseder, Jurgen; Domingo, A.; Hirschmann, Alina; Hoeflich, Peter; Lebrun, F.; Renaud, M; Soldi, Simona; Elias-Rosa, Nancy; Hernanz Carbó, Margarita; Kulebi, Baybar; Zhang, X.; Badenes, C.; Domínguez Aguilera, Inmaculada; Garcia Senz, Domingo; Jordi, Carme; Lichti, G.; Vedrenne, G.; von Ballmoos, Peter
    Astronomy and astrophysics
    Date of publication: 2013-04
    Journal article

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  • A Super-solar metallicity for the progenitor of Kepler's supernova

     Park, Sangwook; Badenes Montoliu, Carles; Mori, Koji; Kaida, Ryohei; Bravo Guil, Eduardo; Schenck, Andrew; Eriksen, Kristoffer A.; Hughes, John P.; Slane, Patrick O.; Burrows, David N.; Lee, Jae-Joon
    The astrophysical journal letters
    Date of publication: 2013-04
    Journal article

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    We have performed deep X-ray observations of the remnant of Kepler's supernova (SN 1604) as a Key Project of the Suzaku Observatory. Our main goal is to detect secondary Fe-peak elements in the supernova (SN) ejecta to gain insights into the Type Ia SN explosion mechanism and the nature of the progenitor. Here, we report our initial results. We made a conclusive detection of X-ray emission lines from highly ionized Mn, Cr, and Ni as well as Fe. The observed Mn-to-Cr line flux ratio is ~0.60, ~30% larger than that measured in Tycho's remnant. We estimate an Mn-to-Cr mass ratio of ~0.77, which is strongly suggestive of a large neutron excess in the progenitor star before the onset of the thermonuclear runaway. The observed Ni-to-Fe line flux ratio (~0.03) corresponds to a mass ratio of ~0.06, which is generally consistent with the products of the explosive Si-burning regime in Type Ia explosion models, and rules out contamination from the products of neutron-rich nuclear statistical equilibrium in the shocked ejecta. Together with the previously suggested luminous nature of the explosion, these mass ratios provide strong evidence for a super-solar metallicity in the SN progenitor (~3 Z ¿). Kepler's SN was likely the thermonuclear explosion of a white dwarf formed in the recent past that must have exploded through a relatively prompt channel.

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    Insights into thermonuclear supernovae from the incomplete Si-burning process  Open access

     Bravo Guil, Eduardo
    Astronomy and astrophysics
    Date of publication: 2013-01-21
    Journal article

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    Type Ia supernova (SNIa) explosions synthesize a few tenths to several tenths of a solar mass, whose composition is the result of incomplete silicon burning that reaches peak temperatures of 4 GK to 5 GK. The elemental abundances are sensitive to the physical conditions in the explosion, making their measurement a promising clue to uncovering the properties of the progenitor star and of the explosion itself. Using a parameterized description of the thermodynamic history of matter undergoing incomplete silicon burning, we computed the final composition for a range of parameters wide enough to encompass current models of SNIa. Then, we searched for combinations of elemental abundances that trace the parameters values and are potentially measurable. For this purpose, we divide the present study into two epochs of SNIa, namely the optical epoch, from a few weeks to several months after the explosion, and the X-ray epoch, which refers to the time period in which the supernova remnant is young, starting one or two hundred years age and ending a thousand years after the event. During the optical epoch, the only SNIa property that can be extracted from the detection of incomplete silicon burning elements is the neutron excess of the progenitor white dwarf at thermal runaway, which can be determined through measuring the ratio of the abundance of manganese to that of titanium, chromium, or vanadium. Conversely, in the X-ray epoch, any abundance ratio built using a couple of elements from titanium, vanadium, chromium, or manganese may constrain the initial neutron excess. Furthermore, measuring the ratio of the abundances of vanadium to manganese in the X-ray might shed light on the timescale of the thermonuclear explosion.

    Type Ia supernova (SNIa) explosions synthesize a few tenths to several tenths of a solar mass, whose composition is the result of incomplete silicon burning that reaches peak temperatures of 4 GK to 5 GK. The elemental abundances are sensitive to the physical conditions in the explosion, making their measurement a promising clue to uncovering the properties of the progenitor star and of the explosion itself. Using a parameterized description of the thermodynamic history of matter undergoing incomplete silicon burning, we computed the final composition for a range of parameters wide enough to encompass current models of SNIa. Then, we searched for combinations of elemental abundances that trace the parameters values and are potentially measurable. For this purpose, we divide the present study into two epochs of SNIa, namely the optical epoch, from a few weeks to several months after the explosion, and the X-ray epoch, which refers to the time period in which the supernova remnant is young, starting one or two hundred years age and ending a thousand years after the event. During the optical epoch, the only SNIa property that can be extracted from the detection of incomplete silicon burning elements is the neutron excess of the progenitor white dwarf at thermal runaway, which can be determined through measuring the ratio of the abundance of manganese to that of titanium, chromium, or vanadium. Conversely, in the X-ray epoch, any abundance ratio built using a couple of elements from titanium, vanadium, chromium, or manganese may constrain the initial neutron excess. Furthermore, measuring the ratio of the abundances of vanadium to manganese in the X-ray might shed light on the timescale of the thermonuclear explosion.

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    Sensitivity study of explosive nucleosynthesis in type Ia supernovae : modification of individual thermonuclear reaction rates  Open access

     Bravo Guil, Eduardo; Martínez Pinedo, Gabriel
    Physical review C
    Date of publication: 2012-05-18
    Journal article

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    Background: Type Ia supernovae contribute significantly to the nucleosynthesis of many Fe-group and intermediate-mass elements. However, the robustness of nucleosynthesis obtained via models of this class of explosions has not been studied in depth until now. Purpose: We explore the sensitivity of the nucleosynthesis resulting from thermonuclear explosions of massive white dwarfs with respect to uncertainties in nuclear reaction rates. We put particular emphasis on indentifying the individual reactions rates that most strongly affect the isotopic products of these supernovae. Method: We have adopted a standard one-dimensional delayed detonation model of the explosion of a Chandrasekhar-mass white dwarf and have postprocessed the thermodynamic trajectories of every mass shellwith a nucleosynthetic code to obtain the chemical composition of the ejected matter. We have considered increases (decreases) by a factor of 10 on the rates of 1196 nuclear reactions (simultaneously with their inverse reactions), repeating the nucleosynthesis calculations after modification of each reaction rate pair. We have computed as well hydrodynamic models for different rates of the fusion reactions of 12C and of 16O. From the calculations we have selected the reactions that have the largest impact on the supernova yields, and we have computed again the nucleosynthesis using two or three alternative prescriptions for their rates, taken from the JINA REACLIB database. For the three reactions with the largest sensitivity we have analyzed as well the temperature ranges where a modification of their rates has the strongest effect on nucleosynthesis. Results: The nucleosynthesis resulting from the type Ia supernova models is quite robust with respect to variations of nuclear reaction rates,with the exception of the reaction of fusion of two 12C nuclei. The energy of the explosion changes by less than ~4% when the rates of the reactions 12C + 12C or 16O + 16O are multiplied by a factor of ×10 or ×0.1.

    Background: Type Ia supernovae contribute significantly to the nucleosynthesis of many Fe-group and intermediate-mass elements. However, the robustness of nucleosynthesis obtained via models of this class of explosions has not been studied in depth until now. Purpose: We explore the sensitivity of the nucleosynthesis resulting from thermonuclear explosions of massive white dwarfs with respect to uncertainties in nuclear reaction rates. We put particular emphasis on indentifying the individual reactions rates that most strongly affect the isotopic products of these supernovae. Method: We have adopted a standard one-dimensional delayed detonation model of the explosion of a Chandrasekhar-mass white dwarf and have postprocessed the thermodynamic trajectories of every mass shellwith a nucleosynthetic code to obtain the chemical composition of the ejected matter. We have considered increases (decreases) by a factor of 10 on the rates of 1196 nuclear reactions (simultaneously with their inverse reactions), repeating the nucleosynthesis calculations after modification of each reaction rate pair. We have computed as well hydrodynamic models for different rates of the fusion reactions of 12C and of 16O. From the calculations we have selected the reactions that have the largest impact on the supernova yields, and we have computed again the nucleosynthesis using two or three alternative prescriptions for their rates, taken from the JINA REACLIB database. For the three reactions with the largest sensitivity we have analyzed as well the temperature ranges where a modification of their rates has the strongest effect on nucleosynthesis. Results: The nucleosynthesis resulting from the type Ia supernova models is quite robust with respect to variations of nuclear reaction rates,with the exception of the reaction of fusion of two 12C nuclei. The energy of the explosion changes by less than ∼4% when the rates of the reactions 12C + 12C or 16O + 16O are multiplied by a factor of ×10 or ×0.1. The changes in the nucleosynthesis owing to the modification of the rates of these fusion reactions are also quite modest; for instance, no species with a mass fraction larger than 0.02 experiences a variation of its yield larger than a factor of 2. We provide the sensitivity of the yields of the most abundant species with respect to the rates of the most intense reactions with protons, neutrons, and α. In general, the yields of Fe-group nuclei are more robust than the yields of intermediate-mass elements. Among the species with yields larger than 10−8M , 35S has the largest sensitivity to the nuclear reaction rates. It is remarkable that the reactions involving elements with Z > 22 have a tiny influence on the supernova nucleosynthesis. Among the charged-particle reactions, the most influential on supernova nucleosynthesis are 30Si + p 31P + γ , 20Ne + α 24Mg + γ , and 24Mg + α 27Al + p. The temperatures at which a modification of their rate has a larger impact are in the range 2 T 4 GK.

  • Últimos estadios de la evolución estelar en sistemas binarios: novas clásicas y recurrentes, supernovas, erupciones de rayos X ....

     Bravo Guil, Eduardo; Longland, Richard Leigh; Parikh, Anuj Ramesh; Garcia Senz, Domingo; José Pont, Jordi
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  • Constraints on the gamma-ray emission of SN 2011fe after the maximum of light as obtained by INTEGRAL/SPI

     Isern Vilaboy, Jordi; Jean, Pierre; Bravo Guil, Eduardo; Jürgen, Knodlseder; Diehl, Roland; Domingo, A.; Hirschmann, Alina; Höflich, P.; Elias-Rosa, Nancy; Zhang, X.; Badenes, Carles; Domínguez, Inmaculada; Hernanz Carbó, Margarita; Kulebi, Baybar; Jordi, Carme; Lichti, G.; Vedrenne, G.; von Ballmoos, Peter
    Date: 2011-12-23
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  • Bounds to the gamma--ray flux emitted by SN 2011fe before the maximum of light as obtained by INTEGRAL/SPI

     Isern Vilaboy, Jordi; Jean, Pierre; Bravo Guil, Eduardo; Jürgen, Knodlseder; Diehl, Roland; Hirschmann, Alina; Elias-Rosa, Nancy; Domínguez, Inmaculada; Badenes, C.; Hernanz Carbó, Margarita; Kulebi, Baybar; Jordi, Carme; Lichti, G.; Vedrenne, G.; von Ballmoos, Peter
    Date: 2011-10-14
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    Is the metallicity of their host galaxies a good measure of the metallicity of Type Ia supernovae?  Open access

     Bravo Guil, Eduardo; Badenes, C.
    Monthly notices of the Royal Astronomical Society
    Date of publication: 2011-06
    Journal article

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    The efficient use of Type Ia supernovae (SNIa) for cosmological studies requires knowledge of any parameter that can affect their luminosity in either systematic or statistical ways. Observational samples of SNIa commonly use the metallicity of the host galaxy, Zhost, as an estimator of the supernova progenitor metallicity, ZIa, that is one of the primary factors affecting SNIa magnitude. Here, we present a theoretical study of the relationship between ZIa and Zhost. We follow the chemical evolution of homogeneous galaxy models together with the evolution of the supernova rates in order to evaluate the metallicity distribution function, MDF( Z), i.e. the probability that the logarithm of the metallicity of a SNIa exploding now differs in less than Z from that of its host. We analyse several model galaxies aimed to represent from active to passive galaxies, including dwarf galaxies prone to experience supernova driven outflows. We analyse as well the sensitivity of the MDF to the most uncertain ingredients of our approach: IMF, star-formation law, stellar lifetime, stellar yields, and SNIa delay-time distribution (DTD). Our results show a remarkable degree of agreement between the mean ¯ZIa in a galaxy and its Zhost when they both are measured as the CNO abundance, especially if the DTD peaks at small time delays, while the average Fe abundance of host and SNIa may differ up to 0.4-0.6 dex in passive galaxies. The dispersion of ZIa in active galaxy models is quite small, meaning that Zhost is a quite good estimator of the supernovametallicity. Passive galaxies present a larger dispersion, which is more pronounced in low mass galaxies.We present a procedure to generate random SNIa metallicities, given the host metallicity.

    The efficient use of Type Ia supernovae (SNIa) for cosmological studies requires knowledge of any parameter that can affect their luminosity in either systematic or statistical ways. Observational samples of SNIa commonly use the metallicity of the host galaxy, Zhost, as an estimator of the supernova progenitor metallicity, ZIa, that is one of the primary factors affecting SNIa magnitude. Here, we present a theoretical study of the relationship between ZIa and Zhost. We follow the chemical evolution of homogeneous galaxy models together with the evolution of the supernova rates in order to evaluate the metallicity distribution function, MDF( Z), i.e. the probability that the logarithm of the metallicity of a SNIa exploding now differs in less than Z from that of its host. We analyse several model galaxies aimed to represent from active to passive galaxies, including dwarf galaxies prone to experience supernova driven outflows. We analyse as well the sensitivity of the MDF to the most uncertain ingredients of our approach: IMF, star-formation law, stellar lifetime, stellar yields, and SNIa delay-time distribution (DTD). Our results show a remarkable degree of agreement between the mean ¯ZIa in a galaxy and its Zhost when they both are measured as the CNO abundance, especially if the DTD peaks at small time delays, while the average Fe abundance of host and SNIa may differ up to 0.4-0.6 dex in passive galaxies. The dispersion of ZIa in active galaxy models is quite small, meaning that Zhost is a quite good estimator of the supernovametallicity. Passive galaxies present a larger dispersion, which is more pronounced in low mass galaxies.We present a procedure to generate random SNIa metallicities, given the host metallicity. We also discuss the use of differentmetallicity indicators: Fe vs. O, and gas-phasemetallicity vs. stellar metallicity. Finally, the results of the application of our formalism to a galactic catalogue (VESPA) suggest that SNIa come, in average, from small metallicity progenitors both at low redshifts (contrary to expectations) and in galaxies with high star-formation activity. In spite of large uncertainties in the metallicities derived from the catalogue, the gross trends of ¯ZIa vs. Zhost obtained from VESPA for different galaxy types are roughly consistent with our theoretical estimates.

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    Type Ia supernovae and the 12C+12C reaction rate  Open access

     Bravo Guil, Eduardo; Piersanti, Luciano; Domínguez, Inmaculada; Straniero, Oscar; Isern Vilaboy, Jorge; Escartin Vigo, Jose Antonio
    Astronomy and astrophysics
    Date of publication: 2011-11-22
    Journal article

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    Even if the 12C+12C reaction plays a central role in the ignition of type Ia supernovae (SNIa), the experimental determination of its cross-section at astrophysically relevant energies (E ¿ 2 MeV) has never been made. The profusion of resonances throughout the measured energy range has led to speculation that there is an unknown resonance at E0 ~ 1.5 MeV possibly as strong as the one measured for the resonance at 2.14 MeV, i.e. (¿¿)R = 0.13 meV. Aims. We study the implications that such a resonance would have for our knowledge of the physics of SNIa, paying special attention to the phases that go from the crossing of the ignition curve to the dynamical event. We use one-dimensional hydrostatic and hydrodynamic codes to follow the evolution of accreting white dwarfs until they grow close to the Chandrasekhar mass and explode as SNIa. In our simulations, we account for a low-energy resonance by exploring the parameter space allowed by experimental data. A change in the 12C+12C rate similar to the one explored here would have profound consequences for the physical conditions in the SNIa explosion, namely the central density, neutronization, thermal profile, mass of the convective core, location of the runaway hot spot, or time elapsed since crossing the ignition curve. For instance, with the largest resonance strength we use, the time elapsed since crossing the ignition curve to the supernova event is shorter by a factor ten than for models using the standard rate of 12C+12C, and the runaway temperature is reduced from ~8.14 × 108 K to ~ 4.26 × 108 K. On the other hand, a resonance at 1.5 MeV, with a strength ten thousand times smaller than the one measured at 2.14 MeV, but with an a/p yield ratio substantially different from 1 would have a sizeable impact on the degree of neutronization of matter during carbon simmering. A robust understanding of the links between SNIa properties and their progenitors will not be attained until the 12C+12C reaction rate is measured at energies ~1.5 MeV.

    Context. Even if the 12C+12C reaction plays a central role in the ignition of type Ia supernovae (SNIa), the experimental determination of its cross-section at astrophysically relevant energies (E ≲ 2 MeV) has never been made. The profusion of resonances throughout the measured energy range has led to speculation that there is an unknown resonance at E0 ~ 1.5 MeV possibly as strong as the one measured for the resonance at 2.14 MeV, i.e. (ωγ)R = 0.13 meV. Aims. We study the implications that such a resonance would have for our knowledge of the physics of SNIa, paying special attention to the phases that go from the crossing of the ignition curve to the dynamical event. Methods. We use one-dimensional hydrostatic and hydrodynamic codes to follow the evolution of accreting white dwarfs until they grow close to the Chandrasekhar mass and explode as SNIa. In our simulations, we account for a low-energy resonance by exploring the parameter space allowed by experimental data. Results. A change in the 12C+12C rate similar to the one explored here would have profound consequences for the physical conditions in the SNIa explosion, namely the central density, neutronization, thermal profile, mass of the convective core, location of the runaway hot spot, or time elapsed since crossing the ignition curve. For instance, with the largest resonance strength we use, the time elapsed since crossing the ignition curve to the supernova event is shorter by a factor ten than for models using the standard rate of 12C+12C, and the runaway temperature is reduced from ~8.14 × 108 K to ~ 4.26 × 108 K. On the other hand, a resonance at 1.5 MeV, with a strength ten thousand times smaller than the one measured at 2.14 MeV, but with an α/p yield ratio substantially different from 1 would have a sizeable impact on the degree of neutronization of matter during carbon simmering. Conclusions. A robust understanding of the links between SNIa properties and their progenitors will not be attained until the 12C+12C reaction rate is measured at energies ~1.5 MeV.

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    Computer simulations using implicit Lagrangian hydrodynamics in 3D  Open access

     Escartin Vigo, Jose Antonio; Garcia Senz, Domingo; Bravo Guil, Eduardo
    Reunion de la Sociedad Española de Astronomia
    Presentation's date: 2010-09-14
    Presentation of work at congresses

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    The method known as Smoothed Particle Hydrodynamics (SPH) is an important tool in modern numerical Astrophysics. It has been extensively used to simulate a large number of systems ranging from planets to clusters of galaxies. Nevertheless current applications of the method are restricted to dynamical situations because of the limitations in the time-step imposed by the Courant condition. Here we describe the main features of a new implicit SPH code which is able to handle with several thousand particles and, therefore, it can be used to simulate slowly evolving systems.

  • Metallicity as a source of dispersion in the SNIa bolometric light curve luminosity-width relationship

     Bravo Guil, Eduardo; Domínguez, Inmaculada; Badenes, Carles; Piersanti, Luciano; Straniero, Oscar
    Astrophysical journal
    Date of publication: 2010-02-18
    Journal article

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    The recognition that the metallicity of Type Ia supernova (SNIa) progenitors might bias their use for cosmological applications has led to an increasing interest in its role in shaping SNIa light curves. We explore the sensitivity of the synthesized mass of 56Ni, M(56Ni), to the progenitor metallicity starting from pre-main-sequence models with masses M0 = 2¿7 M_ and metallicities Z = 10-5¿0.10. The interplay between convective mixing and carbon burning during the simmering phase eventually raises the neutron excess, ¿, and leads to a smaller 56Ni yield, but does not change substantially the dependence of M(56Ni) on Z. Uncertain attributes of the progenitor white dwarf, like the central density, have a minor effect on M(56Ni). Our main results are: (1) a sizeable amount of 56Ni is synthesized during incomplete Si-burning, which leads to a stronger dependence of M(56Ni) on Z than obtained by assuming that 56Ni is produced in material that burns fully to nuclear statistical equilibrium; (2) in onedimensional delayed detonation simulations a composition dependence of the deflagration-to-detonation transition (DDT) density gives a nonlinear relationship betweenM(56Ni) and Z and predicts a luminosity larger than previously thought at low metallicities (however, the progenitor metallicity alone cannot explain the whole observational scatter of SNIa luminosities); and (3) an accurate measurement of the slope of the Hubble residuals versus metallicity for a large enough data set of SNIa might give clues to the physics of DDT in thermonuclear explosions.

    The recognition that the metallicity of Type Ia supernova (SNIa) progenitors might bias their use for cosmological applications has led to an increasing interest in its role in shaping SNIa light curves. We explore the sensitivity of the synthesized mass of 56Ni, M(56Ni), to the progenitor metallicity starting from pre-main-sequence models with masses M0 = 2–7 M_ and metallicities Z = 10−5–0.10. The interplay between convective mixing and carbon burning during the simmering phase eventually raises the neutron excess, η, and leads to a smaller 56Ni yield, but does not change substantially the dependence of M(56Ni) on Z. Uncertain attributes of the progenitor white dwarf, like the central density, have a minor effect on M(56Ni). Our main results are: (1) a sizeable amount of 56Ni is synthesized during incomplete Si-burning, which leads to a stronger dependence of M(56Ni) on Z than obtained by assuming that 56Ni is produced in material that burns fully to nuclear statistical equilibrium; (2) in onedimensional delayed detonation simulations a composition dependence of the deflagration-to-detonation transition (DDT) density gives a nonlinear relationship betweenM(56Ni) and Z and predicts a luminosity larger than previously thought at low metallicities (however, the progenitor metallicity alone cannot explain the whole observational scatter of SNIa luminosities); and (3) an accurate measurement of the slope of the Hubble residuals versus metallicity for a large enough data set of SNIa might give clues to the physics of DDT in thermonuclear explosions.

  • Physics of compact objects: I.Theorical modeling and observations of stellar explosions

     Casanova Bustamante, Jordi; Sala Cladellas, Gloria; Loren Aguilar, Pablo; Camacho Díaz, Judit; Renedo Rouco, Isabel; Garcia-berro Montilla, Enrique; Bravo Guil, Eduardo; Garcia Senz, Domingo; Torres Gil, Santiago; Longland, Richard Leigh; Parikh, Anuj Ramesh; José Pont, Jordi
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    The impact of chemical differentiation of white dwarfs on thermonuclear supernovae  Open access

     Bravo Guil, Eduardo; Althaus, Leandro G.; Garcia-berro Montilla, Enrique; Domínguez, Inmaculada
    Astronomy and astrophysics
    Date of publication: 2010-12-16
    Journal article

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    Aims. Gravitational settling of 22Ne in cooling white dwarfs can affect the outcome of thermonuclear supernovae. We investigate how the supernova energetics and nucleosynthesis are in turn influenced by this process. We use realistic chemical profiles derived from state-of-the-art white dwarf cooling sequences. The cooling sequences provide a link between the white dwarf chemical structure and the age of the supernova progenitor system. Methods. The cooling sequence of a 1 M white dwarf was computed until freezing using an up-to-date stellar evolutionary code. We computed explosions of both Chandrasekhar mass and sub-Chandrasekhar mass white dwarfs, assuming spherical symmetry and neglecting convective mixing during the pre-supernova carbon simmering phase to maximize the effects of chemical separation. Results. Neither gravitational settling of 22Ne nor chemical differentiation of 12C and 16O have an appreciable impact on the properties of type Ia supernovae, unless there is a direct dependence of the flame properties (density of transition from deflagration to detonation) on the chemical composition. At a fixed transition density, the maximum variation in the supernova magnitude obtained from progenitors of different ages is ~0.06 mag, and even assuming an unrealistically large diffusion coefficient of 22Ne it would be less than ~0.09 mag. However, if the transition density depends on the chemical composition (all other things being equal) the oldest SNIa can be as much as 0.4 mag brighter than the youngest ones (in our models the age difference is 7.4 Gyr). In addition, our results show that 22Ne sedimentation cannot be invoked to account for the formation of a central core of stable neutron-rich Fe-group nuclei in the ejecta of sub-Chandrasekhar models, as required by observations of type Ia supernovae.

    Aims. Gravitational settling of 22Ne in cooling white dwarfs can affect the outcome of thermonuclear supernovae. We investigate how the supernova energetics and nucleosynthesis are in turn influenced by this process. We use realistic chemical profiles derived from state-of-the-art white dwarf cooling sequences. The cooling sequences provide a link between the white dwarf chemical structure and the age of the supernova progenitor system. Methods. The cooling sequence of a 1 M white dwarf was computed until freezing using an up-to-date stellar evolutionary code. We computed explosions of both Chandrasekhar mass and sub-Chandrasekhar mass white dwarfs, assuming spherical symmetry and neglecting convective mixing during the pre-supernova carbon simmering phase to maximize the effects of chemical separation. Results. Neither gravitational settling of 22Ne nor chemical differentiation of 12C and 16O have an appreciable impact on the properties of type Ia supernovae, unless there is a direct dependence of the flame properties (density of transition from deflagration to detonation) on the chemical composition. At a fixed transition density, the maximum variation in the supernova magnitude obtained from progenitors of different ages is ∼0.06 mag, and even assuming an unrealistically large diffusion coefficient of 22Ne it would be less than ∼0.09 mag. However, if the transition density depends on the chemical composition (all other things being equal) the oldest SNIa can be as much as 0.4 mag brighter than the youngest ones (in our models the age difference is 7.4 Gyr). In addition, our results show that 22Ne sedimentation cannot be invoked to account for the formation of a central core of stable neutron-rich Fe-group nuclei in the ejecta of sub-Chandrasekhar models, as required by observations of type Ia supernovae.

  • Pulsating reverse detonation models of Type Ia supernovae. I. Detonation ignition

     Bravo Guil, Eduardo; Garcia Senz, Domingo
    Astrophysical journal
    Date of publication: 2009-04
    Journal article

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    Observational evidences point to a common explosion mechanism of Type Ia supernovae based on a delayed detonation of a white dwarf (WD). Although several scenarios have been proposed and explored by means of one, two, and three-dimensional simulations, the key point still is the understanding of the conditions under which a stable detonation can form in a destabilized WD. One of the possibilities that have been invoked is that an inefficient deflagration leads to the pulsation of a Chandrasekhar-mass WD, followed by formation of an accretion shock around a carbon-oxygen rich core. The accretion shock confines the core and transforms kinetic energy from the collapsing halo into thermal energy of the core, until an inward moving detonation is formed. This chain of events has been termed Pulsating Reverse Detonation (PRD). In this work we explore the robustness of the detonation ignition for different PRD models characterized by the amount of mass burned during the deflagration phase, Mdefl. The evolution of the WD up to the formation of the accretion shock has been followed with a three-dimensional hydrodynamical code with nuclear reactions turned off. We found that detonation conditions are achieved for a wide range of Mdefl. However, if the nuclear energy released during the deflagration phase is close to the WD binding energy (~0.46 × 1051 erg ¿ Mdefl ~ 0.30 M¿) the accretion shock cannot heat and confine the core efficiently and detonation conditions are not robustly achieved.

  • Gamma-Ray Emission of Type Ia Supernovae.

     Hirschmann, Alina
    Defense's date: 2009-07-03
    Department of Physics and Nuclear Engineering, Universitat Politècnica de Catalunya
    Theses

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  • Pulsating reverse detonation models of Type Ia supernovae. II. Explosion

     Bravo Guil, Eduardo; Garcia Senz, Domingo; Cabezón Gómez, Rubén Martín; Domínguez, I
    Astrophysical journal
    Date of publication: 2009-04
    Journal article

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    Observational evidences point to a common explosion mechanism of Type Ia supernovae based on a delayed detonation of a white dwarf (WD). However, all attempts to ¿nd a convincing ignition mechanism based on a delayed detonation in a destabilized, expanding, white dwarf have been elusive so far. One of the possibilities that has been invoked is that an inef¿cient de¿agration leads to pulsation of a Chandrasekhar-mass WD, followed by formation of an accretion shock that con¿nes a carbon¿oxygen rich core, while transforming the kinetic energy of the collapsing halo into thermal energy of the core, until an inward moving detonation is formed. This chain of events has been termed Pulsating Reverse Detonation (PRD). In this work, we present three-dimensional numerical simulations of PRD models from the time of detonation initiation up to homologous expansion. Different models characterized by the amount of mass burned during the de¿agration phase, Mde¿, give explosions spanning a range of kinetic energies, K ~ (1.0¿1.2)×1051 erg, and 56Ni masses, M(56Ni) ~ 0.6¿0.8 M , which are compatible with what is expected for typical Type Ia supernovae. Spectra and light curves of angle-averaged spherically symmetric versions of the PRD models are discussed. Type Ia supernova spectra pose the most stringent requirements on PRD models.

  • GRUP D'ASTRONOMIA I ASTROFÍSICA

     Torres Gil, Santiago; Renedo Rouco, Isabel; Cabezón Gómez, Rubén Martín; González Villafranca, Alberto; Diaz Aguiló, Marc; José Pont, Jordi; Bravo Guil, Eduardo; Riera Mora, M. Angeles; Garcia Senz, Domingo; Loren Aguilar, Pablo; Sala Cladellas, Gloria; Escartin Vigo, Jose Antonio; Camacho Díaz, Judit; Casanova Bustamante, Jordi; Garcia-berro Montilla, Enrique
    Participation in a competitive project

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    Axisymmetric smoothed particle hydrodynamics with self-gravity  Open access

     Garcia Senz, Domingo; Relano, A; Cabezón Gómez, Rubén Martín; Bravo Guil, Eduardo
    Monthly notices of the Royal Astronomical Society
    Date of publication: 2009-01
    Journal article

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    The axisymmetric form of the hydrodynamic equations within the smoothed particle hydrodynamics (SPH) formalism is presented and checked using idealized scenarios taken from astrophysics (free fall collapse, implosion and further pulsation of a Sun-like star), gas dynamics (wall heating problem, collision of two streams of gas) and inertial confinement fusion (ablative implosion of a small capsule). New material concerning the standard SPH formalism is given. That includes the numerical handling of those mass points which move close to the singularity axis, more accurate expressions for the artificial viscosity and the heat conduction term and an easy way to incorporate self-gravity in the simulations. The algorithm developed to compute gravity does not rely in any sort of grid, leading to a numerical scheme totally compatible with the Lagrangian nature of the SPH equations.

    The axisymmetric form of the hydrodynamic equations within the smoothed particle hydrodynamics (SPH) formalism is presented and checked using idealized scenarios taken from astrophysics (free fall collapse, implosion and further pulsation of a Sun-like star), gas dynamics (wall heating problem, collision of two streams of gas) and inertial confinement fusion (ablative implosion of a small capsule). New material concerning the standard SPH formalism is given. That includes the numerical handling of those mass points which move close to the singularity axis, more accurate expressions for the artificial viscosity and the heat conduction term and an easy way to incorporate self-gravity in the simulations. The algorithm developed to compute gravity does not rely in any sort of grid, leading to a numerical scheme totally compatible with the Lagrangian nature of the SPH equations.

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    Secondary fe-peak nuclei in the tycho supernova remnant  Open access

     Badenes Montoliu, Carles; Bravo Guil, Eduardo; Hughes, John P.
    International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos
    Presentation's date: 2008
    Presentation of work at congresses

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    The Mn to Cr mass ratio in supernova ejecta has recently been proposed as a tracer of Type Ia SN progenitor metallicity. We review the advantages and problems of this observable quantity, and discuss them in the framework of two Galactic supernova remnants: the well known Tycho SNR and W49B, an older object that has been tentatively classified as Type Ia. The fluxes of the Mn and Cr Ka lines in the X-ray spectra of these SNRs observed by the Suzaku and ASCA satellites suggest progenitors of supersolar metallicity for both objects.

  • 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, C; Cassam, G; Bravo Guil, Eduardo; Hughes, John P.
    Astrophysical journal
    Date of publication: 2008-06
    Journal article

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    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 of the O, Si, S, and Fe emission in its X-ray spectrum we conclude that 0509¿67.5 originated ~400 yr ago from a bright, highly energetic Type Ia explosion similar to SN 1991T. Our best model has a kinetic energy of 1.4 × 1051 erg and synthesizes 0.97 M¿ of 56Ni. These results are in excellent agreement with the age estimate and spectroscopy from the light echo. We have thus established the first connection between a Type Ia supernova and its supernova remnant based on a detailed quantitative analysis of both objects.

    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 of the O, Si, S, and Fe emission in its X-ray spectrum we conclude that 0509–67.5 originated ~400 yr ago from a bright, highly energetic Type Ia explosion similar to SN 1991T. Our best model has a kinetic energy of 1.4 × 1051 erg and synthesizes 0.97 M☉ of 56Ni. These results are in excellent agreement with the age estimate and spectroscopy from the light echo. We have thus established the first connection between a Type Ia supernova and its supernova remnant based on a detailed quantitative analysis of both objects.

  • Supernovae in Galactic evolution: direct and indirect metallicity effects

     Bravo Guil, Eduardo; Frölich, C; Hirschi, R; Liebendörfer, M; Thielemann, F -K; Martínez-Pinedo, G
    Date of publication: 2008-08-31
    Book chapter

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  • Type Ia Supernovae

     Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Hirschmann, Alina
    Date of publication: 2008-11-30
    Book chapter

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  • Supernovae and Dark Energy

     Domínguez, Inmaculada; Bravo Guil, Eduardo; Piersanti, Luciano; Straniero, Oscar; Tornambé, Amedeo
    Cosmology Across Cultures
    Presentation of work at congresses

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  • Detection and interpretation of gamma-ray emission from SNIa

     Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Hirschmann, Alina
    New astronomy reviews
    Date of publication: 2008-10
    Journal article

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    The explosion mechanism associated with thermonuclear supernovae (SNIa) is still a matter of debate. Nevertheless, there is a wide agreement that large amounts of radioactive nuclei are produced during these events, which are expected to be strong ¿-ray emitters. In this paper we investigate the usability of these ¿-rays as a diagnostic tool. For this purpose we studied the variety of ¿-ray spectra associated with the different currently-proposed SNIa explosion scenarios: detonation, deflagration, delayed detonation, and pulsating delayed detonation. Our study demonstrates that ¿-ray emission from SNIa is indeed a promising tool, although care must be taken to avoid misinterpretations. We also show that 3D effects can be relevant. They can provide important information about the exploding system and the thermonuclear burning front mechanism if sufficiently-high resolution spectra can be obtained.

    The explosion mechanism associated with thermonuclear supernovae (SNIa) is still a matter of debate. Nevertheless, there is a wide agreement that large amounts of radioactive nuclei are produced during these events, which are expected to be strong γ-ray emitters. In this paper we investigate the usability of these γ-rays as a diagnostic tool. For this purpose we studied the variety of γ-ray spectra associated with the different currently-proposed SNIa explosion scenarios: detonation, deflagration, delayed detonation, and pulsating delayed detonation. Our study demonstrates that γ-ray emission from SNIa is indeed a promising tool, although care must be taken to avoid misinterpretations. We also show that 3D effects can be relevant. They can provide important information about the exploding system and the thermonuclear burning front mechanism if sufficiently-high resolution spectra can be obtained.

  • The end of amnesia: a new method for measuring the metallicity of type Ia supernova progenitors using manganese lines in supernova remnants

     Badenes, C; Bravo Guil, Eduardo; Hughes, John P.
    The astrophysical journal letters
    Date of publication: 2008-06
    Journal article

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    We propose a new method to measure the metallicity of Type Ia supernova progenitors using Mn and Cr lines in the X-ray spectra of young supernova remnants. We show that the Mn-to-Cr mass ratio in Type Ia supernova ejecta is tightly correlated with the initial metallicity of the progenitor, as determined by the neutron excess of the white dwarf material before thermonuclear runaway. We use this correlation, together with the flux of the Cr and Mn Ka X-ray lines in the Tycho supernova remnant recently detected by Suzaku, to derive a metallicity of log (Z) = - 1.32+ 0.67-0.33 for the progenitor of this supernova, which corresponds to log (Z/Z¿) = 0.60+ 0.31-0.60 according to the latest determination of the solar metallicity by Asplund and coworkers. The uncertainty in the measurement is large, but metallicities much smaller than the solar value can be confidently discarded. We discuss the implications of this result for future research on Type Ia supernova progenitors.

    We propose a new method to measure the metallicity of Type Ia supernova progenitors using Mn and Cr lines in the X-ray spectra of young supernova remnants. We show that the Mn-to-Cr mass ratio in Type Ia supernova ejecta is tightly correlated with the initial metallicity of the progenitor, as determined by the neutron excess of the white dwarf material before thermonuclear runaway. We use this correlation, together with the flux of the Cr and Mn Kα X-ray lines in the Tycho supernova remnant recently detected by Suzaku, to derive a metallicity of log (Z) = − 1.32+ 0.67−0.33 for the progenitor of this supernova, which corresponds to log (Z/Z☉) = 0.60+ 0.31−0.60 according to the latest determination of the solar metallicity by Asplund and coworkers. The uncertainty in the measurement is large, but metallicities much smaller than the solar value can be confidently discarded. We discuss the implications of this result for future research on Type Ia supernova progenitors.

  • Detailed spectral modeling of a three-dimensional pulsating reverse detonation model: too much nickel

     Baron, E.; Jeffery, D J; Branch, D; Bravo Guil, Eduardo; Garcia Senz, Domingo; Hauschildt, P H
    Astrophysical journal
    Date of publication: 2008-01
    Journal article

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    We calculate detailed non-LTE synthetic spectra of a pulsating reverse detonation (PRD) model, a novel explosion mechanism for Type Ia supernovae. While the hydro models are calculated in three dimensions, the spectra use an angle-averaged hydro model and thus some of the three-dimensional (3D) details are lost, but the overall average should be a good representation of the average observed spectra. We study the model at three epochs: maximum light, 7 days prior to maximum light, and 5 days after maximum light. At maximum the defining Si II feature is prominent, but there is also a prominent C II feature, not usually observed in normal SNe Ia near maximum. We compare to the early spectrum of SN 2006D, which did show a prominent C II feature, but the fit to the observations is not compelling. Finally, we compare to the postmaximum UV+optical spectrum of SN 1992A. With the broad spectral coverage it is clear that the iron-peak elements on the outside of the model push too much flux to the red and thus the particular PRD realizations studied would be intrinsically far redder than observed SNe Ia. We briefly discuss variations that could improve future PRD models.

    We calculate detailed non-LTE synthetic spectra of a pulsating reverse detonation (PRD) model, a novel explosion mechanism for Type Ia supernovae. While the hydro models are calculated in three dimensions, the spectra use an angle-averaged hydro model and thus some of the three-dimensional (3D) details are lost, but the overall average should be a good representation of the average observed spectra. We study the model at three epochs: maximum light, 7 days prior to maximum light, and 5 days after maximum light. At maximum the defining Si II feature is prominent, but there is also a prominent C II feature, not usually observed in normal SNe Ia near maximum. We compare to the early spectrum of SN 2006D, which did show a prominent C II feature, but the fit to the observations is not compelling. Finally, we compare to the postmaximum UV+optical spectrum of SN 1992A. With the broad spectral coverage it is clear that the iron-peak elements on the outside of the model push too much flux to the red and thus the particular PRD realizations studied would be intrinsically far redder than observed SNe Ia. We briefly discuss variations that could improve future PRD models.

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    A three-dimensional picture of the delayed-detonation model of type Ia supernovae  Open access

     Bravo Guil, Eduardo; Garcia Senz, Domingo
    Astronomy and astrophysics
    Date of publication: 2008-02
    Journal article

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    Deflagration models poorly explain the observed diversity of SNIa. Current multidimensional simulations of SNIa predict a significant amount of, so far unobserved, carbon and oxygen moving at low velocities. It has been proposed that these drawbacks can be resolved if there is a sudden jump to a detonation (delayed detonation), but these kinds of models have been explored mainly in one dimension. Here we present new three-dimensional delayed detonation models in which the deflagraton-to-detonation transition (DDT) takes place in conditions like those favored by one-dimensional models. Methods. We have used a smoothed-particle-hydrodynamics code adapted to follow all the dynamical phases of the explosion, with algorithms devised to handle subsonic as well as supersonic combustion fronts. The starting point was a centrally ignited C¿O white dwarf of 1.38 M. When the average density on the flame surface reached ~2-3 × 107 g cm-3 a detonation was launched. Results. The detonation wave processed more than 0.3 M of carbon and oxygen, emptying the central regions of the ejecta of unburned fuel and raising its kinetic energy close to the fiducial 1051 erg expected from a healthy type Ia supernova. The final amount of 56Ni synthesized also was in the correct range. However, the mass of carbon and oxygen ejected is still too high. Conclusions. The three-dimensional delayed detonation models explored here show an improvement over pure deflagration models, but they still fail to coincide with basic observational constraints. However, there are many aspects of the model that are still poorly known (geometry of flame ignition, mechanism of DDT, properties of detonation waves traversing a mixture of fuel and ashes). Therefore, it will be worth pursuing its exploration to see if a good SNIa model based on the three-dimensional delayed detonation scenario can be obtained.

    Aims. Deflagration models poorly explain the observed diversity of SNIa. Current multidimensional simulations of SNIa predict a significant amount of, so far unobserved, carbon and oxygen moving at low velocities. It has been proposed that these drawbacks can be resolved if there is a sudden jump to a detonation (delayed detonation), but these kinds of models have been explored mainly in one dimension. Here we present new three-dimensional delayed detonation models in which the deflagraton-to-detonation transition (DDT) takes place in conditions like those favored by one-dimensional models. Methods. We have used a smoothed-particle-hydrodynamics code adapted to follow all the dynamical phases of the explosion, with algorithms devised to handle subsonic as well as supersonic combustion fronts. The starting point was a centrally ignited C–O white dwarf of 1.38 M . When the average density on the flame surface reached ∼2−3 × 107 g cm−3 a detonation was launched. Results. The detonation wave processed more than 0.3 M of carbon and oxygen, emptying the central regions of the ejecta of unburned fuel and raising its kinetic energy close to the fiducial 1051 erg expected from a healthy type Ia supernova. The final amount of 56Ni synthesized also was in the correct range. However, the mass of carbon and oxygen ejected is still too high. Conclusions. The three-dimensional delayed detonation models explored here show an improvement over pure deflagration models, but they still fail to coincide with basic observational constraints. However, there are many aspects of the model that are still poorly known (geometry of flame ignition, mechanism of DDT, properties of detonation waves traversing a mixture of fuel and ashes). Therefore, it will be worth pursuing its exploration to see if a good SNIa model based on the three-dimensional delayed detonation scenario can be obtained.

  • Dark energy and thermonuclear supernovae

     Domínguez, I; Bravo Guil, Eduardo; Piersanti, L; Tornambé, A; Straniero, O; Höfflich, P
    Astrophysics Symposium
    Presentation of work at congresses

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  • 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
    Progress in particle and nuclear physics
    Date of publication: 2007-07
    Journal article

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    Nucleosynthesis is the science related to all astrophysical processes which are responsible for the abundances of the elements and their isotopes in the universe. The astrophysical sites are the big bang and stellar objects. The working of nucleosynthesis processes is presented in a survey of events which act as abundance sources. For intermediate-mass and heavy elements, these are stellar evolution, type Ia and core collapse supernovae as well as hypernovae. We discuss successes and failures of existing processes and possible solutions via new (hitherto unknown) processes. Finally an analysis of their role is given in the puzzle to explain the evolution of the elemental and isotopic compositions found in galaxies, and especially the mixture found in the solar system. Different timescales due to the progenitor mass dependence of the endpoints of stellar evolution (type II supernova explosions ¿ SNe II vs. planetary nebulae) or single vs. binary stellar systems (the latter being responsible for novae, type Ia supernovae ¿ SNe Ia, or X-ray bursts) are the keys to understand galactic evolution. At very early times, the role of explosion energies of events, polluting pristine matter with a composition originating only from the big bang, might also play a role. We also speculate on the role of very massive stars not undergoing SN II explosions but rather causing ¿hypernovae¿ after the formation of a central black hole via core collapse.

    Nucleosynthesis is the science related to all astrophysical processes which are responsible for the abundances of the elements and their isotopes in the universe. The astrophysical sites are the big bang and stellar objects. The working of nucleosynthesis processes is presented in a survey of events which act as abundance sources. For intermediate-mass and heavy elements, these are stellar evolution, type Ia and core collapse supernovae as well as hypernovae. We discuss successes and failures of existing processes and possible solutions via new (hitherto unknown) processes. Finally an analysis of their role is given in the puzzle to explain the evolution of the elemental and isotopic compositions found in galaxies, and especially the mixture found in the solar system. Different timescales due to the progenitor mass dependence of the endpoints of stellar evolution (type II supernova explosions — SNe II vs. planetary nebulae) or single vs. binary stellar systems (the latter being responsible for novae, type Ia supernovae — SNe Ia, or X-ray bursts) are the keys to understand galactic evolution. At very early times, the role of explosion energies of events, polluting pristine matter with a composition originating only from the big bang, might also play a role. We also speculate on the role of very massive stars not undergoing SN II explosions but rather causing “hypernovae” after the formation of a central black hole via core collapse.

  • Simulations of radiative shocks and jet formation in laboratory plasmas

     Velarde, Pedro; González, Matthias; Oliva, Eduardo; Kasperczuk, Andrzej; Pisarczyk, Tadeusz; Ullschmied, Jiri; Stehlé, Chantal; Rus, Bedrich; Garcia Senz, Domingo; Bravo Guil, Eduardo; Relaño, Antonio
    5th International conference on inertial fusion sciences and applications : September 9-14, 2007 : Kobe, Japan
    Presentation of work at congresses

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

     Badenes, C; Bravo Guil, Eduardo; Langer, N; Hughes, John P.
    Astrophysical journal
    Date of publication: 2007-06
    Journal article

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    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 the Galaxy (Kepler, Tycho, SN 1006), the Large Magellanic Cloud (0509-67.5, 0519-69.0, N103B), and M31 (SN 1885). We find that optically thick outflows from the white dwarf surface (sometimes known as "accretion winds") with velocities above 200 km s-1 excavate large low-density cavities around the progenitors. Such large cavities are incompatible with the dynamics of the forward shock and the X-ray emission from the shocked ejecta in all the Type Ia remnants that we have examined.

    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 the Galaxy (Kepler, Tycho, SN 1006), the Large Magellanic Cloud (0509-67.5, 0519-69.0, N103B), and M31 (SN 1885). We find that optically thick outflows from the white dwarf surface (sometimes known as "accretion winds") with velocities above 200 km s-1 excavate large low-density cavities around the progenitors. Such large cavities are incompatible with the dynamics of the forward shock and the X-ray emission from the shocked ejecta in all the Type Ia remnants that we have examined.

  • Constraining deflagration models of type Ia supernovae through intermediate-mass elements

     Garcia Senz, Domingo; Bravo Guil, Eduardo; Cabezón Gómez, Rubén Martín; Woosley, S E
    Astrophysical journal
    Date of publication: 2007-05
    Journal article

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    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 a massive white dwarf. Using XIME and adopting the usual hypothesis that the relevant flame speed is actually the turbulent speed on the integral length scale, we have built a simple geometrical approach to model the region where IMEs are thought to be produced. It turns out that a healthy production of IMEs involves the combination of not-too-short expansion times, tc = 0.2 s, and high turbulent intensities. According to our results, it could be difficult to produce much more than 0.2 M¿ of intermediate-mass elements within the standard deflagrative paradigm. The calculations also suggest that the mass of the IMEs scales with the mass of the Fe-peak elements, making it difficult to reconcile energetic explosions with low ejected nickel masses, as in the well-observed supernova SN 1991bg or in SN 1998de. Thus, a large production of Si-peak elements, especially in combination with a low or moderate production of iron, could be better addressed either by the delayed detonation route in standard Chandrasekhar-mass models or, perhaps, by the off-center helium detonation in the sub-Chandrasekhar-mass scenario.

    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 a massive white dwarf. Using XIME and adopting the usual hypothesis that the relevant flame speed is actually the turbulent speed on the integral length scale, we have built a simple geometrical approach to model the region where IMEs are thought to be produced. It turns out that a healthy production of IMEs involves the combination of not-too-short expansion times, τc ≥ 0.2 s, and high turbulent intensities. According to our results, it could be difficult to produce much more than 0.2 M☉ of intermediate-mass elements within the standard deflagrative paradigm. The calculations also suggest that the mass of the IMEs scales with the mass of the Fe-peak elements, making it difficult to reconcile energetic explosions with low ejected nickel masses, as in the well-observed supernova SN 1991bg or in SN 1998de. Thus, a large production of Si-peak elements, especially in combination with a low or moderate production of iron, could be better addressed either by the delayed detonation route in standard Chandrasekhar-mass models or, perhaps, by the off-center helium detonation in the sub-Chandrasekhar-mass scenario.

  • The Stagnation phase of an ICF capsule simulated with an axisymmetrical smoothed particle hydrodynamics code

     Relaño, A; Garcia Senz, Domingo; Bravo Guil, Eduardo
    29th European Conference on Laser Interaction with Matter
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  • The late stages of stellar evolution: stellar explosions and non-interacting white dwarfs in the UV

     Hernanz Carbó, Margarita; Domínguez, Inmaculada; Garcia-berro Montilla, Enrique; Garcia Senz, Domingo; Barstow, M. A.; Bravo Guil, Eduardo; González Riestra, R.; Isern Vilaboy, Jorge; José Pont, Jordi; Torres, S
    The World Space Observatory Ultraviolet (WSO/UV) project-Spain 2003-2005
    Presentation of work at congresses

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

     Badenes, C; Borkowski, K J; Hwang, U; Bravo Guil, Eduardo; Hughes, John P.
    Astrophysical journal
    Date of publication: 2006-07
    Journal article

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    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 the Galaxy (Kepler, Tycho, SN 1006), the Large Magellanic Cloud (0509-67.5, 0519-69.0, N103B), and M31 (SN 1885). We find that optically thick outflows from the white dwarf surface (sometimes known as "accretion winds") with velocities above 200 km s-1 excavate large low-density cavities around the progenitors.

    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 the Galaxy (Kepler, Tycho, SN 1006), the Large Magellanic Cloud (0509-67.5, 0519-69.0, N103B), and M31 (SN 1885). We find that optically thick outflows from the white dwarf surface (sometimes known as "accretion winds") with velocities above 200 km s-1 excavate large low-density cavities around the progenitors. Such large cavities are incompatible with the dynamics of the forward shock and the X-ray emission from the shocked ejecta in all the Type Ia remnants that we have examined.

  • The late stages of stellar evolution: stellar explosions and non-interacting white dwarfs in the UV

     Hernanz Carbó, Margarita; Dominguez, I.; Garcia-berro Montilla, Enrique; Garcia Senz, Domingo; Barstow, M.A.; Bravo Guil, Eduardo; Gonzalez-Riestra, R.; Isern, J.; José Pont, Jordi; Torres Gil, Santiago
    Date of publication: 2006-12
    Book chapter

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  • Termodinámica básica : ejercicios

     Del Barrio Casado, Maria; Bravo Guil, Eduardo; Diez Berart, Sergio; Lana Pons, Francisco Javier; Lopez Perez, David Orencio; Salud Puig, Josep; Tamarit Mur, Jose Luis
    Date of publication: 2006-09
    Book

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  • Photons and positrons in Type Ia supernovae

     Hirschmann, Alina; Bravo Guil, Eduardo; Isern Vilaboy, Jordi
    15th European Workshop on White Dwarfs
    Presentation of work at congresses

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  • Modelización multidimensional de explosiones estelares: novas, erupciones de rayos X y supernovas termonucleares

     José Pont, Jordi; Bravo Guil, Eduardo
    Participation in a competitive project

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  • Gamma-ray emission from thermonuclear supernovae

     Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Hirschmann, Alina
    The multicolored landscape of compact objects and their explosive origins Cefalù 2006 : Cefalù, Sicily, 11-18 June 2006
    Presentation of work at congresses

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  • Type la supernova cosmology from a supernova modeller point of view

     Domínguez, I; Piersanti, L; Bravo Guil, Eduardo; Höflich, P; Straniero, O; Tornambè, A
    The multicolored landscape of compact objects and their explosive origins Cefalù 2006 : Cefalù, Sicily, 11-18 June 2006
    Presentation of work at congresses

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  • Interaction of supernovae remnants: from the circumstellar medium to the terrestrial laboratory

     Velarde, P; Garcia Senz, Domingo; Bravo Guil, Eduardo; Ogando, Francisco; Relaño, A; González, E; Lachaise, M; Oliva, E
    Journal de physique IV
    Date of publication: 2006-06
    Journal article

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  • Beyond the bubble catastrophe of type Ia supernovae: pulsating reverse detonation models

     Bravo Guil, Eduardo; Garcia Senz, Domingo
    The astrophysical journal letters
    Date of publication: 2006-05
    Journal article

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    We describe a mechanism by which a failed deflagration of a Chandrasekhar-mass carbon-oxygen white dwarf can turn into a successful thermonuclear supernova explosion, without invoking an ad hoc high-density deflagration-detonation transition. Following a pulsating phase, an accretion shock develops above a core of 1 M_sun composed of carbon and oxygen, inducing a converging detonation. A three-dimensional simulation of the explosion produced a kinetic energy of 1.05E51 ergs and 0.70 M_sun of 56Ni, ejecting scarcely 0.01 M_sun of C-O moving at low velocities. The mechanism works under quite general conditions and is flexible enough to account for the diversity of normal Type Ia supernovae. In given conditions the detonation might not occur, which would reflect in peculiar signatures in the gamma and UV-wavelengths.

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    Interaction of Supernovae remnants: from the circumstellar medium to the terrestrial laboratory  Open access

     Velarde, P; Garcia Senz, Domingo; Bravo Guil, Eduardo; Ogando, Francisco; Relaño, A; Oliva, E
    Physics of plasmas
    Date of publication: 2006-09
    Journal article

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    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 indicate that both large-scale and small-scale simulations display several common features that can be used to design an experiment aimed to validate the hydrodynamical codes. Of particular interest are the structures found around the juncture of the two colliding shells produced by the interaction of the remnants.

    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 indicate that both large-scale and small-scale simulations display several common features that can be used to design an experiment aimed to validate the hydrodynamical codes. Of particular interest are the structures found around the juncture of the two colliding shells produced by the interaction of the remnants.

  • The science of y-ray spectroscopy

     Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Hirschmann, Alina
    Advances in space research
    Date of publication: 2006-11
    Journal article

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    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 ¿-ray emitters. In this paper we investigate the use of ¿-rays as a diagnostic tool. For this purpose we have performed a complete study of the ¿-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 ¿-ray emission from SNIa is, effectively, a promising tool but that must be carefully used since it can lead to misinterpretations. We also show that 3D effects might be relevant in some circumstances and provide important information about the exploding system and the thermonuclear burning front mechanism if high resolution spectra are obtained.

    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 be carefully used since it can lead to misinterpretations. We also show that 3D effects might be relevant in some circumstances and provide important information about the exploding system and the thermonuclear burning front mechanism if high resolution spectra are obtained.

  • 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
    Astrophysical journal
    Date of publication: 2006-01
    Journal article

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    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, i.e., most strongly, the yields of Fe group nuclei for which an induced piston or thermal bomb treatment will not provide the correct yields because the effect of neutrino interactions is not included. We apply parameterized variations to the neutrino-scattering cross sections in order to mimic in one dimension the possible increase of neutrino luminosities caused by uncertainties in proto-neutron star convection. Alternatively, parameterized variations are applied to the neutrino absorption cross sections on nucleons in the "gain region" to mimic the increase in neutrino energy deposition enabled by convective turnover. We find that both measures lead to similar results, causing explosions and a Ye > 0.5 in the innermost ejected layers, due to the combined effect of a short weak-interaction timescale and a negligible electron degeneracy, unveiling the proton-neutron mass difference. We include all weak interactions (electron and positron capture, ß-decay, neutrino and antineutrino capture on nuclei, and neutrino and antineutrino capture on nucleons) and present first nucleosynthesis results for these innermost ejected layers to discuss how they improve predictions for Fe group nuclei.

    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, i.e., most strongly, the yields of Fe group nuclei for which an induced piston or thermal bomb treatment will not provide the correct yields because the effect of neutrino interactions is not included. We apply parameterized variations to the neutrino-scattering cross sections in order to mimic in one dimension the possible increase of neutrino luminosities caused by uncertainties in proto-neutron star convection. Alternatively, parameterized variations are applied to the neutrino absorption cross sections on nucleons in the "gain region" to mimic the increase in neutrino energy deposition enabled by convective turnover. We find that both measures lead to similar results, causing explosions and a Ye > 0.5 in the innermost ejected layers, due to the combined effect of a short weak-interaction timescale and a negligible electron degeneracy, unveiling the proton-neutron mass difference. We include all weak interactions (electron and positron capture, β-decay, neutrino and antineutrino capture on nuclei, and neutrino and antineutrino capture on nucleons) and present first nucleosynthesis results for these innermost ejected layers to discuss how they improve predictions for Fe group nuclei. The proton-rich environment results in enhanced abundances of 45Sc, 49Ti, and 64Zn as required by chemical evolution studies and observations of low-metallicity stars, as well as appreciable production of nuclei in the mass range up to A = 80.

  • Rotating type Ia SN progenitors: explosion and light curves

     Domínguez, I; Piersanti, L; Bravo Guil, Eduardo; Tornambé, A; Straniero, O; Gagliardi, S
    Astrophysical journal
    Date of publication: 2006-06
    Journal article

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    Based on the rigidly rotating progenitor models found to be able to grow up to the canonical Chandrasekhar mass limit and beyond, and undergo a thermonuclear explosion, we compute the explosions, detailed nucleosynthesis, and corresponding light curves by means of a one-dimensional hydrodynamic code. Our results show that the inclusion of rotation in the evolution of the progenitors determines, in a natural way, a variation in the explosive physical conditions, mainly different explosive ignition densities (2.08 × 109 to 3.34 × 109 g cm-3), total masses (1.39-1.48 M), and binding energies (-5.3 × 1050 to -6.6 × 1050 ergs). Such a spread is related to the rotational velocity at the explosive carbon ignition stage and to the efficiency of angular momentum loss during the last part of the progenitor evolution. We explore the final outcome in the framework of the delayed detonation explosion models by fixing the value of the transition density and by considering two different braking efficiencies. Within the explored parameter space, the bolometric light curves at maximum show differences of ~0.1 mag due to the different amount of 56Ni synthesized during the explosion. Although rigid rotation cannot be considered responsible for the diversities in the observational properties of SNe Ia, it could explain the dispersion in the magnitude at maximum of standardized events. We also find that those models with high ignition densities produce a central remnant in which most of the neutron-rich species synthesized during the explosion are trapped.

    Based on the rigidly rotating progenitor models found to be able to grow up to the canonical Chandrasekhar mass limit and beyond, and undergo a thermonuclear explosion, we compute the explosions, detailed nucleosynthesis, and corresponding light curves by means of a one-dimensional hydrodynamic code. Our results show that the inclusion of rotation in the evolution of the progenitors determines, in a natural way, a variation in the explosive physical conditions, mainly different explosive ignition densities (2.08 × 109 to 3.34 × 109 g cm-3), total masses (1.39-1.48 M), and binding energies (-5.3 × 1050 to -6.6 × 1050 ergs). Such a spread is related to the rotational velocity at the explosive carbon ignition stage and to the efficiency of angular momentum loss during the last part of the progenitor evolution. We explore the final outcome in the framework of the delayed detonation explosion models by fixing the value of the transition density and by considering two different braking efficiencies. Within the explored parameter space, the bolometric light curves at maximum show differences of ~0.1 mag due to the different amount of 56Ni synthesized during the explosion. Although rigid rotation cannot be considered responsible for the diversities in the observational properties of SNe Ia, it could explain the dispersion in the magnitude at maximum of standardized events. We also find that those models with high ignition densities produce a central remnant in which most of the neutron-rich species synthesized during the explosion are trapped.

  • Nucleosynthesis in neutrino-driven supernovae

     Froehlich, C; Hix, W R; Martínez, G; Liebendoerfer, M; Thielemann, F K; Bravo Guil, Eduardo; Langanke, K; Zinner, N T
    New astronomy reviews
    Date of publication: 2006-10
    Journal article

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    Core collapse supernovae are the leading actor in the story of the cosmic origin of the chemical elements. Existing models, which generally assume spherical symmetry and parameterize the explosion, have been able to broadly replicate the observed elemental pattern. However, inclusion of neutrino interactions produces noticeable improvements in the iron peak composition of the ejecta when compared to observations. Neutrino interactions may also provide a supernova source for light p-process nuclei.

    Core collapse supernovae are the leading actor in the story of the cosmic origin of the chemical elements. Existing models, which generally assume spherical symmetry and parameterize the explosion, have been able to broadly replicate the observed elemental pattern. However, inclusion of neutrino interactions produces noticeable improvements in the iron peak composition of the ejecta when compared to observations. Neutrino interactions may also provide a supernova source for light p-process nuclei.

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    Neutrino-induced nucleosynthesis of a > 64 nuclei: the vp process  Open access

     Fröhlich, C; Martínez, G; Liebendörfer, M; Thielemann, F -K; Bravo Guil, Eduardo; Hix, W R; Langanke, K; Zinner, N T
    Physical review letters
    Date of publication: 2006-04
    Journal article

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    We present a new nucleosynthesis process that we denote as the ¿p 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.

    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.

  • Thermal X-ray emission from shocked ejecta in Type Ia supernova remnants. II : parameters affecting the spectrum

     Badenes, C; Borkowski, K J; Bravo Guil, Eduardo
    Astrophysical journal
    Date of publication: 2005-05
    Journal article

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    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 key parameters on the shape of the X-ray spectrum of the ejecta: the density of the ambient medium around the SN progenitor and the efficiency of collisionless electron heating at the reverse shock. We also discuss the performance of recent three-dimensional simulations of Type Ia SN explosions in the context of the X-ray spectra of young SNRs. We find a better agreement with the observations for Type Ia SN models with stratified ejecta than for three-dimensional deflagration models with well-mixed ejecta. We conclude that our grid of Type Ia SNR models can improve our understanding of these objects and their relationship to the SNe that originated them.

    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 key parameters on the shape of the X-ray spectrum of the ejecta: the density of the ambient medium around the SN progenitor and the efficiency of collisionless electron heating at the reverse shock. We also discuss the performance of recent three-dimensional simulations of Type Ia SN explosions in the context of the X-ray spectra of young SNRs. We find a better agreement with the observations for Type Ia SN models with stratified ejecta than for three-dimensional deflagration models with well-mixed ejecta. We conclude that our grid of Type Ia SNR models can improve our understanding of these objects and their relationship to the SNe that originated them.