The Evolution and Explosion of Massive Stars Nuclear Physics - - PowerPoint PPT Presentation

The Evolution and Explosion

• f Massive Stars

Nuclear Physics Issues

• S. E. Woosley, A. Heger,
• T. Rauscher, and R. Hoffman

http://www.supersci.org

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 ...

• f the Big Bang
• f stellar evolution
• f nova and supernova explosions
• f x-ray and γ-ray bursts
• f particle physics
• f the evolution of galaxies and the universe

Stars are gravitationally confined thermonuclear reactors. Each time one runs out of one fuel, contraction and heating ensue, unless degeneracy is encountered. For a star over 8 solar masses the contraction and heating continue until an iron core is made that collapses.

What is a massive star?

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

• f the star.

Each shell burning episode affects the distribution of entropy inside the helium core and the final state

• f 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.

Iron core collapse triggers a catastrophe. The star at death is typically a red supergiant with a highly evolved, compact core of heavy elements.

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), A&A, 306, 167 Paper: Thursday - Janka

First three-dimensional calculation of a core-collapse 15 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 foe 1,000,000 “ 1.15 “ 2.8 foe – 600,000 particles in convection zone 3,000,000 “ in progress

Fryer and Warren (2002)

erg energy Explosion T r

51 4 3

10 3 / 4 ≈ = σ π

Explosive Reprocessing

Rauscher, Heger, Woosley, and Hoffman (2002)

15 M

• nb. 62Ni

Papers: Tuesday: Heger Limongi Maeda Thursday: Nomoto

25 M

Rauscher, Heger, Woosley, & Hoffman (2002)

``There is something fascinating about

• science. One gets such a wholesale return of

conjecture out of such a trifling investment

• f fact.”

Mark Twain in Life on the Mississippi As cited at the beginning of Fowler, Caughlan, and Zimmerman, ARAA, 13, 69, (1975)

PROBLEMS PARTICULAR TO NUCLEAR ASTROPHYSICS

• 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
• f temperature and density

Papers: Tuesday: Motobayashi Thielemann Wednesday Kaeppeler Thursday Schatz Goriely Kajino Friday Smith Rauscher

Specific Nuclear Uncertainties:

• 12C(α,γ)16O
• 22Ne(α,n)25Mg
• 12C(n,γ)13C, 16O(n,γ)17O and
• ther 30 keV (n,γ) 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 > 28
• Photodisintegration rates for

heavy nuclei for the γ−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 (ρ ~ 1011 – 1013) for very heavy nuclei in core collapse (A up to several hundred)- Langanke

(massive stars only)

12C(a,γ)16O Papers: Tuesday Fey Posters: A18 Fynbo A32 Makii A47 Sagara A62 Tsentalovich

2 3 3 12 2 3 12 12 3 , 16 12 12 ,

3 / 6 ( C) / 6 ( C) ( C) ( O) ( C) ( C) dY Y dt dY Y Y Y dt dY Y Y dt

α α α α α α α γ α α γ

ρ λ ρ λ ρ λ ρ λ = − = − =

* Buchmann (1996) Heger, Woosley, & Boyse (2002)

current uncertainty

1.4 - 1.8 M

Heger, Woosley, & Boyse (2002)

uncertainty Heger, Woosley, & Boyse (2002)

CF88

Papers: Monday Sneden Aoki Wednesday Kaeppeler Galino Posters: A64 – Zhang B02 – Tomyo B03 – Tomyo B09 – Sonnabend

Kaeppeler et al. 1994, ApJ, 437, 396

Jaeger et al. 2001, PRL, 87, 30 2501 22Ne(a,n)25Mg

25 M

62Ni (n,γ)63Ni

Bao et al. (2000) 12.5 4 Bao & Kaeppeler (1987) Rauscher and Gu 35.5 4 ber (2002) 4 mb 0.3 mb 5 mb ± ± ±

bigger is better .... Needs measuring. s-wave extrapolation is bad. Are there others?

40K(n,γ)41K (and 40K(n,p)40Ar)

unmeasured (from Raus Bao et al. (2000) cher & Thielemann ! Potential C 31 7 mb

• smochronom

! ) eter ±

Rauscher, Heger, Woosley, and Hoffman (2002)

15 M

• nb. 62Ni

12C (n,γ)13C

Bao & Kaeppeler (1987) 0.2 0.4 b Reffo (1989 PC to Kaeppeler) ~20 b Macklin (1990) 3.2 to 14 b Nagai et al. (1991) 16.8 2.1 b Oshaki et µ µ µ µ ± ±

• al. (1994) 15.4

1.0 b Kikuchi et al. (1998) for higher T µ ±

16O(n,γ)17O

Nagai et al. (1994: NIC5) Allen & Macklin (1971) 0.2 b (also BK87 as used in WW95) 38 b Igashira et al. (1995) 3 4 4 b µ µ µ ±

58,59,60Fe(n,γ)59,60,61Fe

Important for producing 60Fe.

16 17

25 M with and withou t O(n, ) O γ

• Solar Metallicity

Papers: Tuesday Thielemann Friday Rauscher

Hauser-Feshbach applicable for essentially all A>28 except near closed shells.

In general, variation of the Hauser-Feshbach rates results in approximately less than a factor of two variation in the nucleosynthesis of A < 70, but there are exceptions. The agreement will not be nearly so good for A > 70 since these nuclei are made by processes that are out of equilibrium.

Hoffman et al., 1999, ApJ, 521, 735

• nb. Both sets of calculations used experimental rates below A = 28

and both sets employed (nγ) rates that had been normalized, at 30 keV, to Bao and Kaepeller (1987).

(nγ) Cross Sections at 30 keV

The ν-Process

53 56

7 10 neutrinos per second L ~ 10 erg/s in each f 6 per flavor Mean energy around 20 Mev

• lavor

r about x

ν

÷

12 12 * 11 , 11 20 20 * 19 , 19

+ C ( C) B + p C + n + N High e e ( Ne) F + xcitation p energy in the compound nucleu Ne s +

µ τ µ τ

ν ν → → → → → → n etc.

(possibly sensitive to ν flavor mixing)

Papers: Tuesday Langanke Heger Thielemann Wednesday Boyd Thursday Janka Poster A41 – Martinez-Pinedo

25 M Process ν −

• Kolbe & Langanke (2002)

vs Haxton (1990)

Heger, Langanke, & Woosley (2002)

T- and ρ-dependent weak interaction rates affect both nucleosynthesis and presupernova structure.

2 e e

Chandrasekhar Mass Y Prior to collapse weak interactions decrease Y form 0.5 to 0.42 They also assist in the collapse a ecrease th nd d e entropy ∝ ≈

Papers: Tuesday Langanke Posters: A34 – Sampaio A38 – Messner B18 - Borzov

conv Si burning

53,54,55,56 55 56 60

For LMP rates the capture is mostly

• n

Fe, Co, and Ni. For FFN rates, capture on Co dominates

These rates should still be regarded as very uncertain

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.

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

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 ν-induced decay rates and

ν neutral current spallation cross sections

Nucleonic wind, 1 - 10 seconds

Anti-neutrinos are "hotter" than the neutrinos, thus weak equilibrium implies an appreciable neutron excess, typically 60% neutrons, 40% protons

* favored

r-Process Site #1: The Neutrino-powered Wind

sensitive to the density (entropy)

Nucleonic disk

0.50 Z = N Radius Electron Mole Number Neutron-rich 1 Entropy Radius

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.

r-Process Site #2: Accretion Disk Wind

4 9 10 4 14 4 7 9 8 11 12

He( n, ) Be(n, ) Be( , ) C He( , ) He( n, ) Li(n, Be( ,n) ) Li( ,n) C B t α γ α γ α γ γ γ α α γ

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

• f neutrons and protons to alphas (like a neutron-rich

Big Bang).

Neutrino flavor mixing and the r-process

Qian et al. (1995); Qian & Fuller (1995)

e e e

and have higher temperatures than (and ). Mixing of and into would result in a lower Y and conditions more favorable to the r-process. This would have some very interesting implication

e µ τ µ τ

ν ν ν ν ν ν ν s for particle physics.

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.

Qian & Woosley (1996)

A proton-rich wind??

Flavor mixing (e.g., Schirato and Fuller 2002)

6 2

• 3

where is in MeV and is in e ( ) 6.55 10 ( V ) 2 g cm . /

e res

Y x m Cos E E m

ν ν

ρ δ θ δ ≈ For the sun, (δm)2 = 3.7 x 10-5 eV2 and sin2 2θ = 0.8 (large mixing angle solution) For the (controversial) LSND result, (δm)2 is larger, perhaps of order 1 eV2 and the mixing angle is small (S&F02 adopt sin2 2θ = 3.5 x 10-3). In some cases it may be possible to get a wind with Ye > 0.5

the Process in Type II supernovae! rp → −

Thusday - Schatz

Specific Nuclear Uncertainties:

• 12C(α,γ)16O
• 22Ne(α,n)25Mg
• 12C(n,γ)13C, 16O(n,γ)17O and
• ther 30 keV (n,γ) 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 > 28
• Photodisintegration rates for

heavy nuclei for the γ−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 (ρ ~ 1011 – 1013) for very heavy nuclei in core collapse (A up to several hundred)- Langanke

(massive stars only)