Computational (Nuclear) Astrophysics with Parallel Computing Kyujin Kwak Korean Astronomy and Space Science Institute (KASI) KISTI Senmiar August 16, 2012

Outlines Motivation –Introduce parallel computer codes that model various astrophysical phenomena including nuclear astrophysics Astrophysical Phenomena –Nuclear Physics for Astronomy –Observations/Astrophysical Phenomena: stars/stellar ev olution, novae/supernovae, X-ray Bursts, gamma-ray burs ts, neutron stars FLASH: Parallel Computing Hydrodynamics Code –For Nuclear Astrophysics –For Other Astrophysical Phenomena Other (Parallel Computing) Codes –Relativistic Radiation Hydrodynamics for GRBs

Nuclear Physics for Astronomy from

from

Stars From Hipparchus Observations Image from Greg Bothun

Novae H and He accreted from a companion star onto a white -dwarf go through nuclear burning and explodes producing a bright flash of light. If the total mass of accreted material plus the original WD is lar ger than Chandrasekhar limit, it explodes as a supernova (Typ e Ia) rather than a nova.

Supernovae Observations – Type I: No Hydrogen – Type II: Hydrogen Progenitors – Type I: detonation of NS in the binary – Type II: core collapse of a single star

Supernova taxonomy Type I No hydrogen Type Ia Type Ia Presents a singly ionized silicon (Si II) line at nm (nanometers), near peak lightionizedsiliconnm Type IbType Ib/c Weak or no silicon absorption feat ure Type Ib Type Ib Shows a non-ionized helium (He I) line at nmhelium Type Ic Type Ic Weak or no helium Type II Type II Shows hydrogen Type II-P/L/N Type II-P/L/N Type II spectrum throughout Type II-P/L Type II-P/L No narrow lines Type II-P Type II-P Reaches a "plateau" in its light cu rve Type II-L Type II-L Displays a "linear" decrease in its light curve (linear in magnitude ve rsus time). [43] [43] Type IIn Type IIn Some narrow lines Type IIb Type IIb Spectrum changes to become like Type Ib From wikipedia

Formation of Type Ia SN NASA, ESA and A. Feild (STScI)

Type Ia SN as a Standard Candle from

X-ray Bursts Similar to nova except that the accreting star is now neutron st ar: high or low mass X-ray binaries Observations –Repeating with irregular periods –Type I: a sharp rise followed by a slow and gradual decl ine of the luminosity profile –Type II: quick pulse shape, very rarely observed Astronomische Nederlandse Satelliet

Gamma-Ray Bursts Serendipitously discovered in 1960s Long vs Short Bursts – Longer vs Shorter than ~2 seconds – Soft vs Hard gamma-ray photons – Stellar Explosion vs Merger – Host Galaxies with High vs Low Star-Formation Evolution of very massive Pop III stars for long GRBs

Neutron Stars Observed radius and mass of NS are used to constrain the in ternal structure of NS through equation of state from the website of Dr. Matthias Hempel,

Lane-Emden Equation Tolman–Oppenheimer–Volkoff (TOV) equation

Introduction to FLASH Developed as open source at Univ. of Chicago (Fryx ell et al. 2000, ApJS) Modular Package written in Fortran 90 –Multi-dimension Hydrodynamics including MHD and RHD –Parallel Adaptive Mesh Refinement by using PARAMESH –Various physical processes: radiative cooling due to line emission, th ermal diffusion, gravity, particle tracking, ionization of atoms etc. –Can deal with nuclear burning with selected chain reactions

Hydrodynamics mass, momentum and energy conservation including source terms Newtonian Special Relativistic

Nuclear Burning Module in FLASH mass fraction molar abundance mass conservation continuity equation reaction rates

Solve this equation by implicit method, i.e., linear solver (matrix conversion) (e.g., MA28, GIFT)

Nuclear Reaction Networks 13 isotopes with 13 isotopes as above + (pp+CNO) + 19 isotope reaction network

Example: Carbon Detonations Timmes et al. 2000, ApJS t=0 s pressure

Ran 1.5 hours with 32 processors on IBM machine to proceed to 1.6e-7 sec (1785 time steps) Finest spatial resolution = 0.2 cm (128 cells along y-axis)

Ionization Module in FLASH

The Milky Way

Simulational Study of HVCs 2D cylindrical coordinates

Simulational Study of HVCs

Non-Equilibrium Cooling in FLASH Tracing ionization states of abundant elements H, He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni (~200 ionization states)

Example of NEI Cooling Simulations Run on Kraken with 960 cores during 3 days (69,120 CPU hours) Computing time on Kraken awarded through TeraGrid Kraken: 112,896 cores = 9,408 nodes x 12 cores/node (1.17 petaflop) t=1.4 Myr t=0 Myr Temperature: N=512 3

Collision of an HVC with the Galactic Disk

mass, momentum and energy conservation including radiation contribution Newtonian Relativistic Radiation Hydrodynamics

Equations to Solve radiation four-force density in the lab frame radiation transport in the lab frame

Equations to Solve

radiation transport in the comoving frame

Example: Propagation of a Relativistic Jet Relativistic Jet Simulations in Collapsar model (Zhang et al. 2003)

Jet in Collapsar Radiation Hydrodynamics at t=0.759s Hydrodynamics at t=0.750 s density

Vz Radiation Hydrodynamics Hydrodynamics

pressure Radiation Hydrodynamics Hydrodynamics

radiation energy radiation energy flux in z-direction Radiation Properties

Hardware available in Korea Korea Astronomy and Space Science Institute (KASI) –Currently, a linux cluster with 128 CPUs –~1000 CPU linux cluster (with GPU supports for some nodes) with thi s year Korea Institute of Science and Technology Information (KISTI) –TACHYON Ⅱ (SUN B6275): 25,408 CPUs (300 TFLOPS) –TACHYON (SUN B6048): 3,008 CPUs (24 TFLOPS) –GAIA (IBM p595): 640 CPUs (5,888 GFLOPS) –GAIA (IBM p6): 1,536 CPUs (30.7TFLOPS)

Introduction to MESA Modules for Experiments in Stellar Astrophysics (MESA) - developed by Paxton et al. (2011, ApJS, 192, 3) 1D stellar evolution code written in Fortran 90 Modules include - equation of state, opacities, and thermonuclear and weak reactions - additional nuclear reaction networks including JINA Reaclib database (more than 4500 isotopes) - mixing length theory of convection (to complement 1D model) - atmosphere boundary conditions - diffusion and gravitational settling

Reaction Network

Samples

Proposed Activities Any new measurements and calculations can be used as in puts to either stellar evolution or hydrodynamics code with n uclear burning in order to be tested with observation s. Using updated (different) reaction rates (i.e., nuclear physics) may (maybe not yet) causes a lot of differences in the re sults that are obtained from computer models. Running multi-dimensional hydrodynamic simulations with tra cking a large number of isotopes.

X-ray Bursts Using 1300 isotopes (Kepler) Woosley et al. 2004, ApJS

Reaction-Rate-Dependence? JINA REACLIB Cyburt et al. 2010, ApJS