The Experts below are selected from a list of 2280 Experts worldwide ranked by ideXlab platform
Elisabeth Vangioni - One of the best experts on this subject based on the ideXlab platform.
-
precision big bang nucleosynthesis with improved helium 4 predictions
Physics Reports, 2018Co-Authors: Alain Coc, Cyril Pitrou, Jeanphilippe Uzan, Elisabeth VangioniAbstract:Abstract Primordial nucleosynthesis is one of the three historical evidences for the big bang model, together with the expansion of the universe and the cosmic microwave background. There is a good global agreement between the computed primordial abundances of helium-4, deuterium, helium-3 and their values deduced from observations. Now that the number of neutrino families and the baryonic densities have been fixed by laboratory measurements or CMB observations, the model has no free parameter and its predictions are rigid. Since this is the earliest cosmic process for which we a priori know all the physics involved, departure from its predictions could provide hints or constraints on new physics or astrophysics in the early universe. Precision on primordial abundances deduced from observations has recently been drastically improved and reach the percent level for both deuterium and helium-4. Accordingly, the BBN predictions should reach the same level of precision. For most isotopes, the dominant sources of uncertainty come from those on the laboratory Thermonuclear Reactions. This article focuses on helium-4 whose predicted primordial abundance depends essentially on weak interactions which control the neutron–proton ratio. The rates of the various weak interaction processes depend on the experimentally measured neutron lifetime, but also includes numerous corrections that we thoroughly investigate here. They are the radiative, zero-temperature, corrections, finite nucleon mass corrections, finite temperature radiative corrections, weak-magnetism, and QED plasma effects, which are for the first time all included and calculated in a self consistent way, allowing to take into account the correlations between them, and verifying that all satisfy detailed balance. Finally, we include the incomplete neutrino decoupling and claim to reach a 1 0 − 4 accuracy on the helium-4 predicted mass fraction of 0 . 24709 ± 0 . 00017 (when including the uncertainty on the neutron lifetime). In addition, we provide a Mathematica primordial nucleosynthesis code that incorporates, not only these corrections but also a full network of Reactions, using the best available Thermonuclear reaction rates, allowing the predictions of primordial abundances of helium-4, deuterium, helium-3 and lithium-7 but also of heavier isotopes up to the CNO region.
-
precision big bang nucleosynthesis with improved helium 4 predictions
arXiv: Cosmology and Nongalactic Astrophysics, 2018Co-Authors: Alain Coc, Cyril Pitrou, Jeanphilippe Uzan, Elisabeth VangioniAbstract:Primordial nucleosynthesis is one of the three historical evidences for the big bang model, together with the expansion of the universe and the cosmic microwave background. Now that the number of neutrino families and the baryonic densities have been fixed by laboratory measurements or CMB observations, the model has no free parameter and its predictions are rigid. Departure from its predictions could provide hints or constraints on new physics or astrophysics in the early universe. Precision on primordial abundances deduced from observations have recently been drastically improved and reach the percent level for both deuterium and helium-4. Accordingly, the BBN predictions should reach the same level of precision. For most isotopes, the dominant sources of uncertainty come from those on the laboratory Thermonuclear Reactions. This article focuses on helium-4 whose predicted primordial abundance depends essentially on weak interactions which control the neutron-proton ratio. The rates of the various weak interaction processes depend on the experimentally measured neutron lifetime, but also includes numerous corrections that we thoroughly investigate here. They are the radiative, zero-temperature, corrections, finite nucleon mass corrections, finite temperature radiative corrections, weak-magnetism, and QED plasma effects, which are for the first time all included and calculated in a self consistent way, allowing to take into account the correlations between them, and verifying that all satisfy detailed balance. The helium-4 predicted mass fraction is $0.24709\pm0.00017$. In addition, we provide a Mathematica code (PRIMAT) that incorporates, not only these corrections but also a full network of Reactions, using the best available Thermonuclear reaction rates, allowing the predictions of primordial abundances up to the CNO region.
Karen Camarda - One of the best experts on this subject based on the ideXlab platform.
-
relativistic tidal disruption and nuclear ignition of white dwarf stars by intermediate mass black holes
The Astrophysical Journal, 2018Co-Authors: Peter Anninos, Chris P Fragile, Samuel S Olivier, R D Hoffman, Bhupendra Mishra, Karen CamardaAbstract:We present results from general relativistic calculations of the tidal disruption of white dwarf stars from near encounters with intermediate-mass black holes. We follow the evolution of 0.2 M ⊙ and 0.6 M ⊙ stars on parabolic trajectories that approach 103–104 M ⊙ black holes as close as a few Schwarzschild radii at periapsis, paying particular attention to the effect that tidal disruption has on Thermonuclear Reactions and the synthesis of intermediate-mass to heavy elements. These encounters create diverse Thermonuclear environments that are characteristic of Type I supernovae and capable of producing both intermediate-mass and heavy elements in arbitrary ratios, depending on the strength (or proximity) of the interaction. Nuclear ignition is triggered in all of our calculations, even at weak tidal strengths β ~ 2.6 and large periapsis radius R P ~ 28 Schwarzschild radii. A strong inverse correlation exists between the mass ratio of calcium-group to iron-group elements and tidal strength, with β 5 producing predominantly calcium-rich debris. At these moderate to weak interactions, nucleosynthesis is not especially efficient, limiting the total mass and outflows of calcium-group elements to <15% of available nuclear fuel. Iron-group elements, however, continue to be produced in greater quantity and ratio with increasing tidal strength, peaking at ~60% mass conversion efficiency in our closest encounter cases. These events generate short bursts of gravitational waves with characteristic frequencies 0.1–0.7 Hz and strain amplitudes from 0.5 × 10−22 to 3.5 × 10−22 at a source distance of 10 Mpc.
-
relativistic tidal disruption and nuclear ignition of white dwarf stars by intermediate mass black holes
arXiv: High Energy Astrophysical Phenomena, 2018Co-Authors: Peter Anninos, Chris P Fragile, Samuel S Olivier, R D Hoffman, Bhupendra Mishra, Karen CamardaAbstract:We present results from general relativistic calculations of the tidal disruption of white dwarf stars from near encounters with intermediate mass black holes. We follow the evolution of 0.2 and $0.6 M_\odot$ stars on parabolic trajectories that approach $10^3$ - $10^4 M_\odot$ black holes as close as a few Schwarzschild radii at periapsis, paying particular attention to the effect tidal disruption has on Thermonuclear Reactions and the synthesis of intermediate to heavy ion elements. These encounters create diverse Thermonuclear environments characteristic of Type I supernovae and capable of producing both intermediate and heavy mass elements in arbitrary ratios, depending on the strength (or proximity) of the interaction. Nuclear ignition is triggered in all of our calculations, even at weak tidal strengths $\beta \sim 2.6$ and large periapsis radius $R_P \sim 28$ Schwarzschild radii. A strong inverse correlation exists between the mass ratio of calcium to iron group elements and tidal strength, with $\beta \lesssim 5$ producing predominately calcium-rich debris. At these moderate to weak interactions, nucleosynthesis is not especially efficient, limiting the total mass and outflows of calcium group elements to $< 15$\% of available nuclear fuel. Iron group elements however continue to be produced in greater quantity and ratio with increasing tidal strength, peaking at $\sim 60$\% mass conversion efficiency in our closest encounter cases. These events generate short bursts of gravitational waves with characteristic frequencies 0.1-0.7 Hz and strain amplitudes $0.5\times10^{-22}$ - $3.5\times10^{-22}$ at 10 Mpc source distance.
Bhupendra Mishra - One of the best experts on this subject based on the ideXlab platform.
-
relativistic tidal disruption and nuclear ignition of white dwarf stars by intermediate mass black holes
The Astrophysical Journal, 2018Co-Authors: Peter Anninos, Chris P Fragile, Samuel S Olivier, R D Hoffman, Bhupendra Mishra, Karen CamardaAbstract:We present results from general relativistic calculations of the tidal disruption of white dwarf stars from near encounters with intermediate-mass black holes. We follow the evolution of 0.2 M ⊙ and 0.6 M ⊙ stars on parabolic trajectories that approach 103–104 M ⊙ black holes as close as a few Schwarzschild radii at periapsis, paying particular attention to the effect that tidal disruption has on Thermonuclear Reactions and the synthesis of intermediate-mass to heavy elements. These encounters create diverse Thermonuclear environments that are characteristic of Type I supernovae and capable of producing both intermediate-mass and heavy elements in arbitrary ratios, depending on the strength (or proximity) of the interaction. Nuclear ignition is triggered in all of our calculations, even at weak tidal strengths β ~ 2.6 and large periapsis radius R P ~ 28 Schwarzschild radii. A strong inverse correlation exists between the mass ratio of calcium-group to iron-group elements and tidal strength, with β 5 producing predominantly calcium-rich debris. At these moderate to weak interactions, nucleosynthesis is not especially efficient, limiting the total mass and outflows of calcium-group elements to <15% of available nuclear fuel. Iron-group elements, however, continue to be produced in greater quantity and ratio with increasing tidal strength, peaking at ~60% mass conversion efficiency in our closest encounter cases. These events generate short bursts of gravitational waves with characteristic frequencies 0.1–0.7 Hz and strain amplitudes from 0.5 × 10−22 to 3.5 × 10−22 at a source distance of 10 Mpc.
-
relativistic tidal disruption and nuclear ignition of white dwarf stars by intermediate mass black holes
arXiv: High Energy Astrophysical Phenomena, 2018Co-Authors: Peter Anninos, Chris P Fragile, Samuel S Olivier, R D Hoffman, Bhupendra Mishra, Karen CamardaAbstract:We present results from general relativistic calculations of the tidal disruption of white dwarf stars from near encounters with intermediate mass black holes. We follow the evolution of 0.2 and $0.6 M_\odot$ stars on parabolic trajectories that approach $10^3$ - $10^4 M_\odot$ black holes as close as a few Schwarzschild radii at periapsis, paying particular attention to the effect tidal disruption has on Thermonuclear Reactions and the synthesis of intermediate to heavy ion elements. These encounters create diverse Thermonuclear environments characteristic of Type I supernovae and capable of producing both intermediate and heavy mass elements in arbitrary ratios, depending on the strength (or proximity) of the interaction. Nuclear ignition is triggered in all of our calculations, even at weak tidal strengths $\beta \sim 2.6$ and large periapsis radius $R_P \sim 28$ Schwarzschild radii. A strong inverse correlation exists between the mass ratio of calcium to iron group elements and tidal strength, with $\beta \lesssim 5$ producing predominately calcium-rich debris. At these moderate to weak interactions, nucleosynthesis is not especially efficient, limiting the total mass and outflows of calcium group elements to $< 15$\% of available nuclear fuel. Iron group elements however continue to be produced in greater quantity and ratio with increasing tidal strength, peaking at $\sim 60$\% mass conversion efficiency in our closest encounter cases. These events generate short bursts of gravitational waves with characteristic frequencies 0.1-0.7 Hz and strain amplitudes $0.5\times10^{-22}$ - $3.5\times10^{-22}$ at 10 Mpc source distance.
Chris P Fragile - One of the best experts on this subject based on the ideXlab platform.
-
relativistic tidal disruption and nuclear ignition of white dwarf stars by intermediate mass black holes
The Astrophysical Journal, 2018Co-Authors: Peter Anninos, Chris P Fragile, Samuel S Olivier, R D Hoffman, Bhupendra Mishra, Karen CamardaAbstract:We present results from general relativistic calculations of the tidal disruption of white dwarf stars from near encounters with intermediate-mass black holes. We follow the evolution of 0.2 M ⊙ and 0.6 M ⊙ stars on parabolic trajectories that approach 103–104 M ⊙ black holes as close as a few Schwarzschild radii at periapsis, paying particular attention to the effect that tidal disruption has on Thermonuclear Reactions and the synthesis of intermediate-mass to heavy elements. These encounters create diverse Thermonuclear environments that are characteristic of Type I supernovae and capable of producing both intermediate-mass and heavy elements in arbitrary ratios, depending on the strength (or proximity) of the interaction. Nuclear ignition is triggered in all of our calculations, even at weak tidal strengths β ~ 2.6 and large periapsis radius R P ~ 28 Schwarzschild radii. A strong inverse correlation exists between the mass ratio of calcium-group to iron-group elements and tidal strength, with β 5 producing predominantly calcium-rich debris. At these moderate to weak interactions, nucleosynthesis is not especially efficient, limiting the total mass and outflows of calcium-group elements to <15% of available nuclear fuel. Iron-group elements, however, continue to be produced in greater quantity and ratio with increasing tidal strength, peaking at ~60% mass conversion efficiency in our closest encounter cases. These events generate short bursts of gravitational waves with characteristic frequencies 0.1–0.7 Hz and strain amplitudes from 0.5 × 10−22 to 3.5 × 10−22 at a source distance of 10 Mpc.
-
relativistic tidal disruption and nuclear ignition of white dwarf stars by intermediate mass black holes
arXiv: High Energy Astrophysical Phenomena, 2018Co-Authors: Peter Anninos, Chris P Fragile, Samuel S Olivier, R D Hoffman, Bhupendra Mishra, Karen CamardaAbstract:We present results from general relativistic calculations of the tidal disruption of white dwarf stars from near encounters with intermediate mass black holes. We follow the evolution of 0.2 and $0.6 M_\odot$ stars on parabolic trajectories that approach $10^3$ - $10^4 M_\odot$ black holes as close as a few Schwarzschild radii at periapsis, paying particular attention to the effect tidal disruption has on Thermonuclear Reactions and the synthesis of intermediate to heavy ion elements. These encounters create diverse Thermonuclear environments characteristic of Type I supernovae and capable of producing both intermediate and heavy mass elements in arbitrary ratios, depending on the strength (or proximity) of the interaction. Nuclear ignition is triggered in all of our calculations, even at weak tidal strengths $\beta \sim 2.6$ and large periapsis radius $R_P \sim 28$ Schwarzschild radii. A strong inverse correlation exists between the mass ratio of calcium to iron group elements and tidal strength, with $\beta \lesssim 5$ producing predominately calcium-rich debris. At these moderate to weak interactions, nucleosynthesis is not especially efficient, limiting the total mass and outflows of calcium group elements to $< 15$\% of available nuclear fuel. Iron group elements however continue to be produced in greater quantity and ratio with increasing tidal strength, peaking at $\sim 60$\% mass conversion efficiency in our closest encounter cases. These events generate short bursts of gravitational waves with characteristic frequencies 0.1-0.7 Hz and strain amplitudes $0.5\times10^{-22}$ - $3.5\times10^{-22}$ at 10 Mpc source distance.
G Chabrier - One of the best experts on this subject based on the ideXlab platform.
-
Thermonuclear fusion in dense stars electron screening conductive cooling and magnetic field effects
Astronomy and Astrophysics, 2012Co-Authors: A Y Potekhin, G ChabrierAbstract:We study the plasma correlation effects on nonresonant Thermonuclear Reactions of carbon and oxygen in the interiors of white dwarfs and liquid envelopes of neutron stars. We examine the effects of electron screening on thermodynamic enhancement of Thermonuclear Reactions in dense plasmas beyond the linear mixing rule. Using these improved enhancement factors, we calculate carbon and oxygen ignition curves in white dwarfs and neutron stars. The energy balance and ignition conditions in neutron star envelopes are evaluated, taking their detailed thermal structure into account. The result is compared to the simplified “one-zone model”, which is routinely used in the literature. We also consider the effect of strong magnetic fields on the ignition curves in the ocean of magnetars.
