The Evolution and Explosion of 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 ... of the Big Bang of stellar evolution of nova and supernova explosions of x-ray and -ray bursts of particle physics of the evolution of galaxies and the universe

Stars are gravitationallyconfined thermonuclear reactors.Each time one runs out of onefuel, contraction and heatingensue, unless degeneracy isencountered.

For a star over 8 solar massesthe contraction and heatingcontinue until an iron core is made that collapses.

What is a massive star?

The advanced burning stagesare characterized by multiplephases of core and shell burning.The nature and number of suchphases varies with the massof the star.

Each shell burning episodeaffects the distribution of entropy inside the helium core and the final stateof the star (e.g., iron coremass) can be non-monotonicand, to some extent, chaotic.

Neutrino losses are higherand the central carbon abundancelower in stars of higher mass.

Iron core collapse triggers a catastrophe. The star at death is typically a red supergiant with a highlyevolved, 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-collapse15 solar mass supernova.

This figure shows the iso-velocitycontours (1000 km/s) 60 ms aftercore bounce in a collapsing massivestar. Calculated by Fryer and Warrenat 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 zone3,000,000 “ in progress

Fryer and Warren (2002)

ergenergyExplosionTr 5143 103/4

ExplosiveReprocessing

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 ofconjecture out of such a trifling investment of fact.”

Mark Twain in Life on the Mississippi

As cited at the beginning of Fowler, Caughlan, andZimmerman, 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 of temperature and density

Papers:

Tuesday: Motobayashi Thielemann

Wednesday Kaeppeler

Thursday Schatz Goriely Kajino

Friday Smith Rauscher

Specific Nuclear Uncertainties:

• 12C()16O

• 22Ne(,n)25Mg

• 12C(n,)13C, 16O(n,)17O and other 30 keV (n,) 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 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 (~ 1011 – 1013) for very heavy nuclei in core collapse (A up to several hundred)- Langanke

(massive stars only)

12C(a,)16O

Papers:

Tuesday Fey

Posters:

A18 FynboA32 MakiiA47 SagaraA62 Tsentalovich

2 33

122 3 12 12

3 ,

1612 12

,

3 / 6

( C)/ 6 ( C) ( C)

( O)( C) ( C)

dYY

dt

dYY Y Y

dt

dYY Y

dt

* Buchmann (1996)

Heger, Woosley, & Boyse (2002)

currentuncertainty

1.4 - 1.8 M

Heger, Woosley, & Boyse (2002)

uncertainty

Heger, Woosley, & Boyse (2002)

CF88

Papers:

Monday Sneden AokiWednesday Kaeppeler Galino

Posters:

A64 – ZhangB02 – TomyoB03 – TomyoB09 – Sonnabend

Kaeppeler et al. 1994, ApJ, 437, 396

Jaeger et al. 2001, PRL, 87, 30 2501

22Ne(a,n)25Mg

25 M

62Ni (n,)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,)41K (and 40K(n,p)40Ar)

unmeasured

(from Raus

Bao et al. (2000)

cher & Thielemann

!

Potential C

31 7 mb

osmochronom !

)

eter

Rauscher, Heger, Woosley, and Hoffman (2002)

15 M

nb. 62Ni

12C (n,)13CBao & 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

al. (1994) 15.4 1.0 b

Kikuchi et al. (1998) for higher T

16O(n,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

58,59,60Fe(n,)59,60,61Fe Important for producing 60Fe.

16 17

25 M

with and withou

t O(n, ) O

Solar Metallicity

Papers:

Tuesday Thielemann

Friday Rauscher

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

In general, variation of the Hauser-Feshbach rates results in approximately less thana 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 (n) rates that had been normalized, at 30 keV, to Bao and Kaepeller (1987).

(n) Cross Sections at 30 keV

The -Process

53

567 10 neutrinos per second

L ~ 10 erg/s

in each f

6 per flavor

Mean energy around 20 Mev

o

lavor

r about x

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

+

n

etc. (possibly sensitive to flavor mixing)

Papers:

Tuesday Langanke Heger Thielemann

Wednesday Boyd

Thursday Janka

Poster

A41 – Martinez-Pinedo

25 M

Process

Kolbe & Langanke (2002)vs

Haxton (1990)

Heger, Langanke, & Woosley (2002)

T- and -dependent weak interaction ratesaffect both nucleosynthesis and presupernovastructure.

2e

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 – SampaioA38 – MessnerB18 - Borzov

conv Si burning

53,54,55,56 55

56

60

For LMP rates the

capture is mostly

on Fe, Co,

and Ni.

For FFN rates,

capture on Co

dominates

These ratesshould still beregarded as veryuncertain

Different choices of ratescan give quite different results for key quantities atiron core collapse.

Most of the difference here comes from WW95 usingbeta decay rates that wereway too small.

Need to know rates onnuclei heavier than mass60 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 - HondaB30 – 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 -induced decay rates and neutral current spallation cross sections

Nucleonic wind, 1 - 10 seconds

Anti-neutrinos are "hotter" thanthe neutrinos, thus weak equilibriumimplies 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

ElectronMole Number

Neutron-rich

1

Entropy

Radius

The disk responsiblefor rapidly feeding ablack 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 neutronexcess.

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

Bt

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 reassemblyof neutrons and protons to alphas (like a neutron-richBig 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

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 resY x m Cos E

E m

For the sun, (m)2 = 3.7 x 10-5 eV2 and sin2 2large mixing angle solution)

For the (controversial) LSND result, (m)2 is larger, perhaps of order 1 eV2 and the mixing angle is small (S&F02 adopt sin2 2= 3.5 x 10-3).

In some cases it may be possible to get a wind withYe > 0.5 the Process in Type II supernovae!rp Thusday - Schatz

Specific Nuclear Uncertainties:

• 12C()16O

• 22Ne(,n)25Mg

• 12C(n,)13C, 16O(n,)17O and other 30 keV (n,) 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 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 (~ 1011 – 1013) for very heavy nuclei in core collapse (A up to several hundred)- Langanke

(massive stars only)