The Evolution and Explosion

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The Evolution and Explosion of Massive
Stars Nuclear Physics Issues
S. E. Woosley, A. Heger, T. Rauscher, and R.
Hoffman
http//www.supersci.org
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We study nuclear astrophysics because The
origin of the elements is an interesting
problem Nuclear transmutation (and gravity)
are the origin of all stellar energy
generation. Nuclear physics determines
stellar structure. We can use that
understanding as a diagnostic ... of
the Big Bang of stellar evolution
of nova and supernova explosions of
x-ray and g-ray bursts of particle
physics of the evolution of galaxies
and the universe
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What is a massive star?
Stars are gravitationally confined
thermonuclear reactors.Each time one runs out of
onefuel, contraction and heating ensue, unless
degeneracy is encountered. For a star over 8
solar massesthe contraction and heating continue
until an iron core is made that collapses.
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The advanced burning stages are characterized by
multiple phases of core and shell burning. The
nature and number of such phases varies with the
mass of the star. Each shell burning
episode affects the distribution of entropy
inside the helium core and the final state of
the star (e.g., iron core mass) can be
non-monotonic and, to some extent,
chaotic. Neutrino losses are higher and the
central carbon abundance lower in stars of higher
mass.
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Iron core collapse triggers a catastrophe. The
star at death is typically a red supergiant
with a highly evolved, compact core of heavy
elements.
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Burrows, Hayes, and Fryxell, (1995), ApJ, 450, 830
15 Solar masses exploded with an energy of
order 1051 erg. see also Janka and Mueller,
(1996), AA, 306, 167
Paper Thursday - Janka
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Fryer and Warren (2002)
First three-dimensional calculation of a
core-collapse15 solar mass supernova.This
figure shows the iso-velocity contours (1000
km/s) 60 ms after core bounce in a collapsing
massive star. Calculated by Fryer and Warren at
LANL using SPH (300,000 particles).
The box is 1000 km across.
300,000 particles 1.15 Msun remnant 2.9
foe1,000,000 1.15
2.8 foe 600,000 particles in convection
zone 3,000,000 in progress
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Explosive Reprocessing
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Rauscher, Heger, Woosley, and Hoffman (2002)
Papers Tuesday Heger Limongi
Maeda Thursday Nomoto
nb. 62Ni
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Rauscher, Heger, Woosley, Hoffman (2002)
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There is something fascinating about
science. One gets such a wholesale return
of conjecture out of such a trifling investment
of fact.
Mark Twain in Life on the Mississippi
As cited at the beginning of Fowler, Caughlan,
and Zimmerman, ARAA, 13, 69, (1975)
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PROBLEMS PARTICULAR TO NUCLEAR ASTROPHYSICS
Papers Tuesday Motobayashi
Thielemann Wednesday Kaeppeler Thursday
Schatz Goriely Kajino Friday Smith
Rauscher

• Both product and target nuclei are frequently
  radioactive
• Targets exist in a thermal distribution of
  excited states
• There are a lot of nuclei and reactions
  (tens of thousands)
• Need weak interaction rates at extreme values
  of temperature and density

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Specific Nuclear Uncertainties
(massive stars only)

• Photodisintegration rates for heavy nuclei
  for the g-process Mohr, Utsunomiya
• Mass excesses and half lives for the
  r-process
• Reaction rates affecting the nucleosynthesis
  of radioactive nuclei 22Na, 26Al, 44Ti,
  56,57Ni, 60Co -Diehl
• The nuclear EOS for core collapse supernovae
  Session 11
• Electron capture rates at high densities (r
  1011 1013) for very heavy nuclei in core
  collapse (A up to several hundred)- Langanke

• 12C(a,g)16O
• 22Ne(a,n)25Mg
• 12C(n,g)13C, 16O(n,g)17O and other 30 keV
  (n,g) cross sections
• Neutrino spallation of 4He, 12C, 16O, 20Ne,
  La, Ta
• Weak rates for the iron group
• Rates for the rp-process in proton- rich
  winds of young neutron stars
• Hauser-Feshbach rates for A gt 28

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12C(a,g)16O
Papers Tuesday Fey
Posters A18 Fynbo A32 Makii A47 Sagara A62
Tsentalovich
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Buchmann (1996)
Heger, Woosley, Boyse (2002)
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Heger, Woosley, Boyse (2002)
current uncertainty
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Heger, Woosley, Boyse (2002)
uncertainty
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CF88
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Papers Monday Sneden Aoki Wednesday
Kaeppeler Galino Posters A64
Zhang B02 Tomyo B03 Tomyo B09 Sonnabend
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Kaeppeler et al. 1994, ApJ, 437, 396
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22Ne(a,n)25Mg
Jaeger et al. 2001, PRL, 87, 30 2501
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62Ni (n,g)63Ni
bigger is better .... Needs measuring. s-wave
extrapolation is bad. Are there others?
40K(n,g)41K (and 40K(n,p)40Ar)
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Rauscher, Heger, Woosley, and Hoffman (2002)
nb. 62Ni
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12C (n,g)13C
16O(n,g)17O
58,59,60Fe(n,g)59,60,61Fe Important for
producing 60Fe.
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Solar Metallicity
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Papers Tuesday Thielemann Friday
Rauscher
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Hauser-Feshbach applicable for essentially all
Agt28except near closed shells.
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Hoffman et al., 1999, ApJ, 521, 735
In general, variation of the Hauser-Feshbach
rates results in approximately less than a factor
of two variation in the nucleosynthesis of A lt
70, but there are exceptions. The agreement will
not be nearly so good for A gt 70 since these
nuclei are made by processes that are out of
equilibrium.
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nb. Both sets of calculations used experimental
rates below A 28 and both sets employed (ng)
rates that had been normalized, at 30 keV, to
Bao and Kaepeller (1987).
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(ng) Cross Sections at 30 keV
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The n-Process
Papers Tuesday Langanke Heger
Thielemann Wednesday Boyd Thursday
Janka Poster A41 Martinez-Pinedo
(possibly sensitive to n flavor mixing)
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Kolbe Langanke (2002) vs Haxton (1990)
Heger, Langanke, Woosley (2002)
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T- and r-dependent weak interaction
rates affect both nucleosynthesis and
presupernova structure.
Papers Tuesday Langanke Posters A34
Sampaio A38 Messner B18 - Borzov
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conv Si burning
These rates should still be regarded as
very uncertain
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Different choices of rates can give quite
different results for key quantities at iron
core collapse. Most of the difference here
comes from WW95 using beta decay rates that
were way too small.
Need to know rates on nuclei heavier than mass 60
at higher temperature and density than 1010.
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The r-Process
Papers Monday Sneden Aoki Wednesday
Nishimura Thursday Goriely Kajino
Sumiyoshi Friday Ryan Takahashi Wanajo

Posters A52 Ishiyama A53 Ishikawa
B36 Ishimaru B38 - Honda B30
Tamamura B31, B32 Terasawa B33-Panov
B39 - Otsuki
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Need

• Binding energies (neutron-separation
  energies) along the r-process path
• Temperature-dependent beta-decay half-lives
  along the r-process path
• May need neutron-induced fission cross
  sections
• May need n-induced decay rates and n neutral
  current spallation cross sections

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r-Process Site 1 The Neutrino-powered Wind
Anti-neutrinos are "hotter" than the neutrinos,
thus weak equilibrium implies an appreciable
neutron excess, typically 60 neutrons, 40
protons
favored

sensitive to the density (entropy)
Nucleonic wind, 1 - 10 seconds
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r-Process Site 2 Accretion Disk Wind
Entropy
The disk responsible for rapidly feeding a black
hole, e.g., in a collapsed star, may dissipate
some of its angular momentum and energy in a
wind. Closer to the hole, the disk is a plasma
of nucleons with an increasing neutron excess.
1
Radius
Nucleonic disk
0.50
Z N
ElectronMole Number
Neutron-rich
Radius
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Reactions governing the assembly to carbon are
critical
(e.g., Terasawa et al (2001))
Also important for the very short time scale
r-process (Meyer 2001) are reactions governing
the reassembly of neutrons and protons to alphas
(like a neutron-rich Big Bang).
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Neutrino flavor mixing and the r-process
Qian et al. (1995) Qian Fuller (1995)
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Neutrino-powered wind p-nuclei
Hoffman, Woosley, Fuller, Meyer , ApJ, 460,
478, (1996)
In addition to being a possible site for the
r-process, the neutrino- powered wind also
produces interesting nucleosynthesis of
p-process nuclei above the iron-group,
especially 64Zn, 70Ge, 74Se, 78Kr, 84Sr,
90,92Zr, and 92Mo. Reaction rate information
in this mass range is non-existant.
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A proton-rich wind??
Qian Woosley (1996)
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Flavor mixing (e.g., Schirato and Fuller 2002)
For the sun, (dm)2 3.7 x 10-5 eV2 and sin2 2q
0.8 (large mixing angle solution) For the
(controversial) LSND result, (dm)2 is larger,
perhaps of order 1 eV2 and the mixing angle is
small (SF02 adopt sin2 2q 3.5 x 10-3). In
some cases it may be possible to get a wind
with Ye gt 0.5
Thusday - Schatz
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Specific Nuclear Uncertainties
(massive stars only)

• Photodisintegration rates for heavy nuclei
  for the g-process Mohr, Utsunomiya
• Mass excesses and half lives for the
  r-process
• Reaction rates affecting the nucleosynthesis
  of radioactive nuclei 22Na, 26Al, 44Ti,
  56,57Ni, 60Co -Diehl
• The nuclear EOS for core collapse supernovae
  Session 11
• Electron capture rates at high densities (r
  1011 1013) for very heavy nuclei in core
  collapse (A up to several hundred)- Langanke

• 12C(a,g)16O
• 22Ne(a,n)25Mg
• 12C(n,g)13C, 16O(n,g)17O and other 30 keV
  (n,g) cross sections
• Neutrino spallation of 4He, 12C, 16O, 20Ne,
  La, Ta
• Weak rates for the iron group
• Rates for the rp-process in proton- rich
  winds of young neutron stars
• Hauser-Feshbach rates for A gt 28