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Jasinta D M Dewi - One of the best experts on this subject based on the ideXlab platform.

  • research note on the binding energy parameter of common envelope evolution dependency on the definition of the stellar core boundary during spiral in
    Astronomy and Astrophysics, 2001
    Co-Authors: Th M Tauris, Jasinta D M Dewi
    Abstract:

    According to the standard picture for binary interactions, the outcome of binaries surviving the evolution through a common envelope (CE) and spiral-in phase is determined by the internal structure of the donor star at the onset of the mass transfer, as well as the poorly-known eciency parameter, CE, for the ejection of the H-envelope of the donor. In this Research Note we discuss the Bifurcation Point which separates the ejected, unprocessed H-rich material from the inner core region of the donor (the central part of the star which will later contract to form a compact object). We demonstrate that the exact location of this Point is very important for evaluating the binding energy parameter, , which is used to determine the post-CE orbital separation. Here we compare various methods to dene the Bifurcation Point (core/envelope boundary) of evolved stars with masses 4, 7, 10 and 20 M. We consider the specic nuclear energy production rate prole, the change in the mass- density gradient (Bisscheroux 1998), the inner region containing less than 10% hydrogen, the method suggested by Han et al. (1994) and the entropy prole. We also calculated eective polytropic index proles. The entropy prole method measures the convective boundary (at the onset of flatness in the specic entropy) which is not equivalent to the core boundary for RGB stars. Hence, this method is not applicable for RGB stars, unless the actual Bifurcation Point of a CE is located at the bottom of the outer convection zone (resulting in larger values of and larger post-CE orbital separations). On the AGB, where highly degenerate and condensed cores are formed, we nd good agreement between the various methods, except for massive (20 M) stars.

  • on the binding energy parameter of common envelope evolution dependency on the definition of the stellar core boundary during spiral in
    Astronomy and Astrophysics, 2001
    Co-Authors: Th M Tauris, Jasinta D M Dewi
    Abstract:

    According to the standard picture for binary interactions, the outcome of binaries surviving the evolution through a common envelope (CE) and spiral-in phase is determined by the internal structure of the donor star at the onset of the mass transfer, as well as the poorly-known eciency parameter, CE, for the ejection of the H-envelope of the donor. In this Research Note we discuss the Bifurcation Point which separates the ejected, unprocessed H-rich material from the inner core region of the donor (the central part of the star which will later contract to form a compact object). We demonstrate that the exact location of this Point is very important for evaluating the binding energy parameter, , which is used to determine the post-CE orbital separation. Here we compare various methods to dene the Bifurcation Point (core/envelope boundary) of evolved stars with masses 4, 7, 10 and 20 M. We consider the specic nuclear energy production rate prole, the change in the mass- density gradient (Bisscheroux 1998), the inner region containing less than 10% hydrogen, the method suggested by Han et al. (1994) and the entropy prole. We also calculated eective polytropic index proles. The entropy prole method measures the convective boundary (at the onset of flatness in the specic entropy) which is not equivalent to the core boundary for RGB stars. Hence, this method is not applicable for RGB stars, unless the actual Bifurcation Point of a CE is located at the bottom of the outer convection zone (resulting in larger values of and larger post-CE orbital separations). On the AGB, where highly degenerate and condensed cores are formed, we nd good agreement between the various methods, except for massive (20 M) stars.

  • on the binding energy parameter of common envelope evolution dependency on the definition of the stellar core boundary during spiral in
    arXiv: Astrophysics, 2001
    Co-Authors: Th M Tauris, Jasinta D M Dewi
    Abstract:

    According to the standard picture for binary interactions, the outcome of binaries surviving the evolution through a common envelope (CE) and spiral-in phase is determined by the internal structure of the donor star at the onset of the mass transfer, as well as the poorly-known efficiency parameter, eta_CE}, for the ejection of the H-envelope of the donor. In this Research Note we discuss the Bifurcation Point which separates the ejected, unprocessed H-rich material from the inner core region of the donor (the central part of the star which will later contract to form a compact object). We demonstrate that the exact location of this Point is very important for evaluating the binding energy parameter, lambda, which is used to determine the post-CE orbital separation. Here we compare various methods to define the Bifurcation Point (core/envelope boundary) of evolved stars with masses 4, 7, 10 and 20 M_sun. We consider the specific nuclear energy production rate profile, the change in the mass-density gradient (Bisscheroux 1998), the inner region containing less than 10% hydrogen, the method suggested by Han et al. (1994) and the entropy profile. We also calculated effective polytropic index profiles. The entropy profile method measures the convective boundary (at the onset of flatness in the specific entropy) which is not equivalent to the core boundary for RGB stars. Hence, this method is not applicable for RGB stars, unless the actual Bifurcation Point of a CE is located at the bottom of the outer convection zone (resulting in larger values of lambda and larger post-CE orbital separations). On the AGB, where highly degenerate and condensed cores are formed, we find good agreement between the various methods, except for massive (20 M_sun) stars.

Th M Tauris - One of the best experts on this subject based on the ideXlab platform.

  • research note on the binding energy parameter of common envelope evolution dependency on the definition of the stellar core boundary during spiral in
    Astronomy and Astrophysics, 2001
    Co-Authors: Th M Tauris, Jasinta D M Dewi
    Abstract:

    According to the standard picture for binary interactions, the outcome of binaries surviving the evolution through a common envelope (CE) and spiral-in phase is determined by the internal structure of the donor star at the onset of the mass transfer, as well as the poorly-known eciency parameter, CE, for the ejection of the H-envelope of the donor. In this Research Note we discuss the Bifurcation Point which separates the ejected, unprocessed H-rich material from the inner core region of the donor (the central part of the star which will later contract to form a compact object). We demonstrate that the exact location of this Point is very important for evaluating the binding energy parameter, , which is used to determine the post-CE orbital separation. Here we compare various methods to dene the Bifurcation Point (core/envelope boundary) of evolved stars with masses 4, 7, 10 and 20 M. We consider the specic nuclear energy production rate prole, the change in the mass- density gradient (Bisscheroux 1998), the inner region containing less than 10% hydrogen, the method suggested by Han et al. (1994) and the entropy prole. We also calculated eective polytropic index proles. The entropy prole method measures the convective boundary (at the onset of flatness in the specic entropy) which is not equivalent to the core boundary for RGB stars. Hence, this method is not applicable for RGB stars, unless the actual Bifurcation Point of a CE is located at the bottom of the outer convection zone (resulting in larger values of and larger post-CE orbital separations). On the AGB, where highly degenerate and condensed cores are formed, we nd good agreement between the various methods, except for massive (20 M) stars.

  • on the binding energy parameter of common envelope evolution dependency on the definition of the stellar core boundary during spiral in
    Astronomy and Astrophysics, 2001
    Co-Authors: Th M Tauris, Jasinta D M Dewi
    Abstract:

    According to the standard picture for binary interactions, the outcome of binaries surviving the evolution through a common envelope (CE) and spiral-in phase is determined by the internal structure of the donor star at the onset of the mass transfer, as well as the poorly-known eciency parameter, CE, for the ejection of the H-envelope of the donor. In this Research Note we discuss the Bifurcation Point which separates the ejected, unprocessed H-rich material from the inner core region of the donor (the central part of the star which will later contract to form a compact object). We demonstrate that the exact location of this Point is very important for evaluating the binding energy parameter, , which is used to determine the post-CE orbital separation. Here we compare various methods to dene the Bifurcation Point (core/envelope boundary) of evolved stars with masses 4, 7, 10 and 20 M. We consider the specic nuclear energy production rate prole, the change in the mass- density gradient (Bisscheroux 1998), the inner region containing less than 10% hydrogen, the method suggested by Han et al. (1994) and the entropy prole. We also calculated eective polytropic index proles. The entropy prole method measures the convective boundary (at the onset of flatness in the specic entropy) which is not equivalent to the core boundary for RGB stars. Hence, this method is not applicable for RGB stars, unless the actual Bifurcation Point of a CE is located at the bottom of the outer convection zone (resulting in larger values of and larger post-CE orbital separations). On the AGB, where highly degenerate and condensed cores are formed, we nd good agreement between the various methods, except for massive (20 M) stars.

  • on the binding energy parameter of common envelope evolution dependency on the definition of the stellar core boundary during spiral in
    arXiv: Astrophysics, 2001
    Co-Authors: Th M Tauris, Jasinta D M Dewi
    Abstract:

    According to the standard picture for binary interactions, the outcome of binaries surviving the evolution through a common envelope (CE) and spiral-in phase is determined by the internal structure of the donor star at the onset of the mass transfer, as well as the poorly-known efficiency parameter, eta_CE}, for the ejection of the H-envelope of the donor. In this Research Note we discuss the Bifurcation Point which separates the ejected, unprocessed H-rich material from the inner core region of the donor (the central part of the star which will later contract to form a compact object). We demonstrate that the exact location of this Point is very important for evaluating the binding energy parameter, lambda, which is used to determine the post-CE orbital separation. Here we compare various methods to define the Bifurcation Point (core/envelope boundary) of evolved stars with masses 4, 7, 10 and 20 M_sun. We consider the specific nuclear energy production rate profile, the change in the mass-density gradient (Bisscheroux 1998), the inner region containing less than 10% hydrogen, the method suggested by Han et al. (1994) and the entropy profile. We also calculated effective polytropic index profiles. The entropy profile method measures the convective boundary (at the onset of flatness in the specific entropy) which is not equivalent to the core boundary for RGB stars. Hence, this method is not applicable for RGB stars, unless the actual Bifurcation Point of a CE is located at the bottom of the outer convection zone (resulting in larger values of lambda and larger post-CE orbital separations). On the AGB, where highly degenerate and condensed cores are formed, we find good agreement between the various methods, except for massive (20 M_sun) stars.

Tonghua Zhang - One of the best experts on this subject based on the ideXlab platform.

Yongli Song - One of the best experts on this subject based on the ideXlab platform.

  • spatiotemporal dynamics in the single population model with memory based diffusion and nonlocal effect
    Journal of Differential Equations, 2019
    Co-Authors: Yongli Song, Hao Wang
    Abstract:

    Abstract To incorporate spatial memory and nonlocal effect of animal movements, we propose and investigate the spatiotemporal dynamics of the single population model with memory-based diffusion and nonlocal reaction. We first study the stability of a positive equilibrium and the steady state Bifurcation induced by diffusion and nonlocality. We then investigate the impact of the averaged memory period on stability and Bifurcation, and show that the combination of the averaged memory period and the diffusion can lead to the occurrence of Turing-Hopf and double Hopf Bifurcations. The paper originally derives the normal form theory for Turing-Hopf Bifurcation in the general reaction-diffusion equation with memory-based diffusion and nonlocal reaction. This novel algorithm can be widely used to classify the spatiotemporal dynamics near the Turing-Hopf Bifurcation Point. Finally, we apply the obtained results to a model proposed by Britton and numerically illustrate the spatiotemporal patterns induced by Hopf, Turing-Hopf and double Hopf Bifurcations. Stable spatially homogeneous/nonhomogeneous periodic solutions, homogeneous/nonhomogeneous steady states and the transition from one of these solutions to another are provided in this paper. We additionally acquire the coexistence of two stable spatially nonhomogeneous steady states or two spatially nonhomogeneous periodic solutions near the Turing-Hopf Bifurcation Point.

  • turing hopf Bifurcation analysis of a predator prey model with herd behavior and cross diffusion
    Nonlinear Dynamics, 2016
    Co-Authors: Xiaosong Tang, Yongli Song, Tonghua Zhang
    Abstract:

    In this paper, we consider a predator–prey model with herd behavior and cross-diffusion subject to homogeneous Neumann boundary condition. Firstly, the existence and priori bound of a solution for the model without cross-diffusion are shown. Then, by computing and analyzing the normal form on the center manifold associated with the Turing–Hopf Bifurcation, we find a wealth of spatiotemporal dynamics near the Turing–Hopf Bifurcation Point under suitable conditions. Furthermore, some numerical simulations to illustrate the theoretical analysis are carried out.

  • spatiotemporal dynamics in a diffusive ratio dependent predator prey model near a hopf turing Bifurcation Point
    Computers & Mathematics With Applications, 2014
    Co-Authors: Yongli Song, Xingfu Zou
    Abstract:

    Abstract Spatiotemporal dynamics in a ratio-dependent predator–prey model with diffusion is studied by analytical methods. Normal forms associated with codimension-two Hopf–Turing Bifurcation are derived, which can be used to understand and classify the spatiotemporal dynamics of the model for values of parameters close to the Hopf–Turing Bifurcation Point. In the vicinity of this degenerate Point, a wealth of complex spatiotemporal dynamics are observed. Our theoretical results are confirmed by numerical simulations.

Salih Djilali - One of the best experts on this subject based on the ideXlab platform.

  • herd behavior in a predator prey model with spatial diffusion Bifurcation analysis and turing instability
    Journal of Applied Mathematics and Computing, 2018
    Co-Authors: Salih Djilali
    Abstract:

    We consider in this paper an ecological model, in a predator–prey interaction with the presence of a herd behavior. For the analysis of the model, the existence of positive solution and also the existence Hopf Bifurcation, Turing driven instability, and Turing–Hopf Bifurcation Point have bee proved. Then by calculating the normal form, on the center of the manifold associated to the Hopf Bifurcation Points, the stability of the periodic solution has been proved. In the last part of the paper, numerical simulations has been given to illustrate our theoretical analysis.