Bulletin of the American Physical Society
APS April Meeting 2012
Volume 57, Number 3
Saturday–Tuesday, March 31–April 3 2012; Atlanta, Georgia
Session H14: Hot Topics in Computational Astrophysics |
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Sponsoring Units: DCOMP DAP Chair: Vicky Kalogera, Northwestern University Room: Grand Hall East C |
Sunday, April 1, 2012 10:45AM - 11:21AM |
H14.00001: The Challenge of Modeling Dense Stellar Systems Invited Speaker: David Merritt Galaxy nuclei and the cores of globular clusters are regions where the density of stars can reach millions per cubic parsec. Modeling the dynamical evolution of such systems is critical for understanding a number of fundamental processes, including core collapse, the creation of massive black holes, and the generation of gravitational waves. But the computational challenges are severe, due to the large range in time scales; the steepness of gravitational force gradients near a massive compact object; the need to include relativistic corrections to the equations of motion; and finite-size (collisional) effects, among other factors. This talk reviews recent progress in this area, with a highlight on the extreme-mass-ratio inspiral (EMRI) problem. [Preview Abstract] |
Sunday, April 1, 2012 11:21AM - 11:33AM |
H14.00002: Relaxation in axisymmetric stellar cusps around black holes Eugene Vasiliev, David Merritt We consider two-body relaxation in flattened axisymmetric stellar cusps around supermassive black holes and associated rates of star capture by the black hole. Inside the black hole radius of influence, the motion of stars in the mean field can be described analytically. Perturbations from discreteness of the mass distribution lead to diffusion of stars in the phase space, which is described by a Fokker-Planck equation. We solve this equation for various values of the capture boundary and degree of flattening, and find that capture rates increase with respect to spherical case, up to a factor of few. We also perform a set of collisional N-body simulations to confirm the predictions of the Fokker-Planck models. We discuss implications for the rates of stellar tidal disruption in nuclear star clusters, and extreme mass ratio inspirals in Milky Way and external galaxies. [Preview Abstract] |
Sunday, April 1, 2012 11:33AM - 12:09PM |
H14.00003: The Changing Landscape of Type Ia Supernova Progenitors Invited Speaker: Chris Fryer In the past, scientists studying progenitors of Type Ia supernova progenitors were faced with a problem getting agreement between the progenitors that population synthesis studies could get in large enough numbers to explain the SNIa population and the progenitors that engine theorists felt worked. This landscape has rapidly changed in the past few years with the dramatic change in our understanding of thermonuclear explosions. I will review the current situation of these engines in the context of supernova progenitors. These new results are prompting new population synthesis studies and I will review some of the recent results in this field. We may be able to distinguish these progenitors based on detailed spectra. I will conclude with a discussion of the current work on SNIa light-curve and spectra calculations and their relevance to SNIa progenitors. [Preview Abstract] |
Sunday, April 1, 2012 12:09PM - 12:21PM |
H14.00004: Cracking the Most Luminous Supernovae: Multidimensional Simulations of Pulsational Pair-Instability Supernovae Ke-Jung Chen, Alexander Heger, Ann Almgren, Stan Woosley The extremely luminous supernovae such as SN 2006gy challenge the traditional view of core collapse supernovae, because they seem too luminous by more than one order of magnitude. Their unusual brightness might be explained by the collisions between shells of matter ejected by these massive stars at the end of their lives, so called pulsational pair-instability supernovae (PPSNe). We present the results from our multidimensional simulations of PPSNe with the state-of-the-art radiation-hydro code, CASTRO. We find significant amounts of fluid instabilities occurred during the shells apostrophe collisions and discuss how the resulting mixing affects the observational signature of PPSNe. [Preview Abstract] |
Sunday, April 1, 2012 12:21PM - 12:33PM |
H14.00005: A New Monte Carlo Method for Velocity-Dependent Neutrino And Photon Transport Ernazar Abdikamalov, Adam Burrows, Frank Loeffler, Christian D. Ott, Erik Schnetter, Evan O'Connor Monte Carlo approaches to radiation transport have several attractive properties compared to deterministic methods. These include simplicity of implementation, high accuracy, and good parallel scaling. Moreover, Monte Carlo methods are relatively easy to extend to multiple spatial dimensions, which makes them particularly interesting in modeling complex astrophysical phenomena such as neutrino transport in core-collapse supernovae. We present a generalization of the Implicit Monte Carlo and Discrete-Diffusion Monte Carlo schemes to multi-energy and velocity-dependent neutrino transport and demonstrate that our scheme represents an attractive approach to modeling neutrino transport in core-collapse supernovae. We also show that our scheme can easily be adapted to photon transport. [Preview Abstract] |
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