Embed Size (px)
Citation preview
Nucleosynthesis in white dwarf
close encounters and collisions
Enrique García-Berro1,2
Gabriela Aznar-Siguán1,2
Pablo Lorén-Aguilar1,2,3
Jordi José1,2
Jordi Isern2,4
1Universitat Politècnica de Catalunya2Institut d’Estudis Espacials de Catalunya
3University of Exeter2,4Institut de Ciències de l’Espai (CSIC)
www.upc.eduOutline
Introduction
Motivation
Smoothed Particle Hydrodynamics
Results
Conclusions
www.upc.eduOutline
Introduction
Motivation
Smoothed Particle Hydrodynamics
Results
Conclusions
www.upc.eduIntroduction
Globular clusters are stellar systems of 104-107 stars, have
high core densities of around 103 pc-3 are old (have ages
around 10-13 Gyr), and contain many degenerate objects.
Also, the central regions of galaxies have very high stellar
densities.
In such a dense environment stars can pass very close one to
another.
During the lifetime of the cluster every star will suffer one or
more of these events.
This leads to the formation of binaries through dynamical
interactions and to the emission of gravitational waves.
www.upc.eduIntroduction
It has been predicted that the white dwarf merger rate leading
to super-Chandrasekhar remnants will be increased by an
order of magnitude through dynamical interactions (Shara &
Hurley 2002).
www.upc.eduOutline
Introduction
Motivation
Smoothed Particle Hydrodynamics
Results
Conclusions
www.upc.eduMotivation
Most of the previous studies of this kind have been performed
either with low resolution, incomplete physical prescriptions or
with limited ranges of masses and chemical compositions.
We have performed a series of high-resolution Smoothed
Particle Hydrodynamics simulations of white dwarf interactions
with three main objectives:
1. Compute their dynamical behavior.
2. Compute the associated nucleosynthesis.
3. Study the different kind of remnants as a function of the
initial conditions.
www.upc.eduOutline
Introduction
Motivation
Smoothed Particle Hydrodynamics
Results
Conclusions
www.upc.eduThe SPH code
Riemann Solver (Monaghan, 1995).
Gravity: binary tree (Barnes & Hut, 1986).
Polynomial kernel (Monaghan & Lattanzio, 1985).
Predictor-corrector (Serna et al. 1996).
We use 4.0 105 particles.
Energy and angular momentum conserved at 0.01% in 104
time steps.
Helmholtz EOS, which includes:
Electrons, Fermi-Dirac integrals.
Ions: ideal plus Coulomb corrections.
Photons.
www.upc.eduThe SPH code
Full set of nuclear reactions:
12C+12C
-chains from He to Zn
He, CO and ONe secondaries.
Neutrino losses (Itoh et al. 1996)
MPI parallelization.
www.upc.eduOutline
Introduction
Motivation
Smoothed Particle Hydrodynamics
Results
Conclusions
www.upc.eduCollisions: setup
We have performed 71+12 simulations of close
encounters of two white dwarfs of different masses,
screening a broad range of parameters.
ω
Star 2
xini
yini
Star 1
ω
www.upc.eduCollisions: summary, 0.6 M
+ 0.8 M
www.upc.eduCollisions: summary, full set
www.upc.eduCollisions: summary, full set
www.upc.eduEccentric binary
www.upc.eduLateral collision: single remnant
www.upc.eduDirect collision: disruption of both stars
www.upc.eduDirect collision: disruption of one star
www.upc.eduOutcomes: 0.6 M
+ 0.8 M
www.upc.eduOutcomes: full set
www.upc.eduNo disruption
www.upc.eduDisruption
www.upc.eduEjected mass
www.upc.eduDebris mass
www.upc.eduAccreted mass
www.upc.eduPeak temperatures
www.upc.eduMetallicity enhancement
www.upc.eduChemical abundances
www.upc.eduMass of 56Ni synthesized
www.upc.eduOutline
Introduction
Motivation
Smoothed Particle Hydrodynamics
Results
Conclusions
www.upc.eduSummary
We have simulated the final state of a wide range of binary
white dwarf close encounters.
The result of such encounters can be either a merger or the
formation of an eccentric double white dwarf. In the case of
mergers can be a direct collision or a lateral one.
In some cases we obtain detonations, which may lead to the
disruption of one or both stars, to super-Chandrasekhar Type Ia
supernovae, or to sub-luminous supernovae.
In all cases we have computed the associated nucleosynthesis.
www.upc.eduSummary
The masses of nickel synthesized have been quantified, as well
as the nucleosynthetic pattern in those interactions in which no
powerful explosion is obtained.
Nucleosynthesis in white dwarf
close encounters and collisions
Enrique García-Berro1,2
Gabriela Aznar-Siguán1,2
Pablo Lorén-Aguilar1,2,3
Jordi José1,2
Jordi Isern2,4
1Universitat Politècnica de Catalunya2Institut d’Estudis Espacials de Catalunya
3University of Exeter2,4Institut de Ciències de l’Espai (CSIC)
