Nuclear Laboratory Data Needs

for Astrophysics

S. E. Woosley,

Alex Heger, andRob Hoffman

with help from Tuguldur Sukhbold, Justin Brown, Michael Wiescher, Thomas Janka, and Roland Diehl

John Poole and S. Woosley (1983)

"There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact."

Mark Twain

and Willy Fowler on many occasions

Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build astructure which has no relation to reality.

- Nikola Tesla

NUCLEAR ASTROPHYSICS

• Requirements for nuclear data are very broad and diverse

We want to understand the origin of every isotope (fortunately not every isotope interacts with every other one!)

Three general areas of application:

Nucleosynthesis – Big Bang, Stars, Novae, Supernovae, Cosmic Rays

Energy Generation – Stars, Sun (including neutrinos), Novae, X-Ray Bursts

Behavior of matter at high density and temperature

PROBLEMS PARTICULAR TO NUCLEAR ASTROPHYSICS

• The relevant energies in the stars are generally much lower than what can be accessed in the laboratory

• Both product and target nuclei are frequently radioactive (tdecay > tHD) • Targets exist in a thermal distribution of excited states

• There are a lot of nuclei and reactions (tens of thousands)

Typical nuclear data deck for stellar nucleosynthesis includes5442 nuclei and 105,000 reactions (plus their inverses). Fortunately not all areequally important. Most (non-r-process) studies use about 1/3 of this.

SOURCES OF DATA

Theory

• Hauser-Feshbach

• R-Matrix analysis

• Direct capture calculations

• Weak interactions as f(T,r)

Laboratory

• Stable targets – (underground), low background, high current

• Unstable beams – e.g., FAIR/GSI, ISAC/TRIUMF, RIBF/RIKEN, ISOLDE/CERN,ATLAS/ARGONNE, NSCL/MSU,FRIB (to come)

• Surrogate reactions, inversereactions, THM, etc.

… and tabulations of all data in a refereed machine usable format –

Rate distributions (a partial list):

https://groups.nscl.msu.edu/jina/reaclib/db/ Cyburt et al ApJS 189, 240 (2010)

Univ California rate set

http://www.astro.ulb.ac.be/bruslib/Xu et al (2012) astroph1212.0628

http://adg.llnl.gov/Research/RRSN/

The Brussels (NACRE2) rate set

The KADONIS (Karlsruhe) rate set for s- and p-processes

The JINA rate set

http://www.kadonis.org

Portal to many collections (ORNL)http://www.nucastrodata.org/datasets.html

… and many more

Yields averaged over a Salpeter (G = 1.35) initial mass function.

Responsible for producing the elements 4 < Z < 39

Isotopic yields for 31 stars averaged over a Salpeter IMF, G = -1.35

Intermediate mass elements(23< A < 60) and s-process (A = 60 – 90) well produced.

Carbon and Oxygen over-produced.

p-process deficient by a factor of ~4 for A > 130 and absent for A < 130

Lately, we have been testing the JINA rate distributions in stellar and supernova models against our older collection of rates.

Four masses of stars 15, 18, 22, and 25 solar masses. Hold structure constant, i.e., use same rates for energy generation, but use new rates for nucleosynthesis.

Used JINA 1.0, version 2.0 in progress (many bugsfound in JINA 1.0)

Results using new ratesResults using old rates

~fac 2 changes (mostly down) for many(ag) and (a,p) reactions on Ca and Ti

31P being destroyed by larger 31P(p,a)28Si rate

Slight overall increase in s-process (even though 22Ne(a,n)25Mg went up by 20%) due to factor of 4 decrease in 22Ne(a,g)26Mg

• New data includes revised partition functions, Q-values, weak decay rates and dozens ofreaction rates.

• No very large changes (> factor 2) found yetfor A < 100 nucleosynthesis but study continues. Larger changes expected for r-process and

rp-process synthesis. Switching to JINA 2.0 now.

• Abundance determinations in the sun and meteorites is now giving agreement to 10%

for most elements. Commensurate accuracy in the stellar models and nuclear physics desired

• Studies like this will help locate regions of uncertainty.

SOME SPECIFIC CURRENT CHALLENGES

1) 12C(a,g)16O (and 3a) – Probably the last remaining uncertain reactions that affect stellar structure as well as nucleosynthesis

2) 22Ne(a,n)25Mg - Main source of neutrons for the s-process. Important diagnostic for which stars actually blow up

3) Reactions affecting the production of 26Al, 44Ti, and 60Fe. Important long lived radioactive gamma-ray line emitters

4) Reactions affecting the rp-process in x-ray bursts andthe r-process of nucleosynthesis (nuclei far from stability)

5) Reactions affecting the solar neutrino flux or Big Bang nucleosynthesis

12C ( a, g ) 16O

Oxygen-16

Low energy data are needed to improve reliability of cross section extrapolation

The relative rates of 3a and 12C(a,g)16Odetermine the proportions of C and Othat come out of helium burning. C and Oare fuels for major subsequent burning stages.

*

uncertainty

Heger, Woosley, & Boyse (2002)Obviously 12C(a,g)16O

affects the nucleosynthesis 12C and 16O, but it also

directly affects the productionof many other species madeby carbon, neon and oxygen

burning.

Many species are successfully coproduced ifthe rate has an S-factor at

300 keV of about 170 keV b

But it also affects the structure of the pre-

supernova star

Density Profiles of Supernova Progenitor Cores

2D SASI-aided, Neutrino-Driven Explosion?

These should beeasy to explode

These will be hardto explode. High binding energy.High prompt accretion rate.

O’Connor and Ott, ApJ, 730, 70, (2011)

Characterize possibility of a neutrino-powered explosion based upon the compactness parameter, z,

If R is small and the 2.5 solar mass point lies close in, then z is big. The star is hard to explode. Based upon a seriesof 1D models OO11 find stars with z over 0.45 are particularlydifficult to explode.

Ugliano et al, ApJ, 757, 69 (2012) find more diversity and get explosions for a smaller value of x, as low as 0.15

Density Profiles of Supernova Progenitor Cores

2D SASI-aided, Neutrino-Driven Explosion?

Large z

Small z

Convective Carbon Core Burning (exoergic)

Strong carbonBurning Shell

Easier to explode

Sukhbold and Woosley (in prep)

Harder to explode

Oconnor and Ott (2011)

~Ugliano et al (2012)

Island ofExplodability?

Stars with very litle mass losse.g., low metallicity stars

(Thomas Janka, PTEP, 2012)

Shock radius as a function of time for 2D simulationsby Janka’s group. All stars but the 25 solar mass modelexplode – at least initially. This includes 27 solar masses

norm. Buchmann (1996)S(300 keV) = 146 keV b

The mass of the maximum mass star that has exoergic carbon coreburning as a function of the 12C(a,g)16O rate. The most likely range of the multiplier here is 0.85 to 1.3 (S(300 keV) = 159 +- 20% keV b).That implies an uncertainty in the mass of 3 to 4 solar masses.

(calculations by Sukhbold)

Current situation (S(300 keV)):

Buchmann (1996) 146 keV b (range 82 – 270)

Buchmann (2005) 145 +- 43 keV b

Kunz et al (2001) 165 +- 50 keV b

Schuermann (2012) 161+- 16 +8-2 (sys) keV b

We use 1.2 * Buchmann = 175 keV b (and have used it for 15 years)

12C ( a, g ) 16O

In progress deBoer et al. R-matrix analysis of ~10,000 experimental data points. Success so far

for 15N(p,g) and 15N(p,a)

Expected accuracy < 10% (Wiescher private communication)

12C(a,g), 12C(a,p), 12C(a,a), 15N(p,g), 15N(p,a), 15N(p,p), and 16N(b-a) including all the various gamma, alpha, and proton decay channels.

Low Energy References

High Energy References

Of equal importance to 12C(a,g)16O is 3a

The current uncertainty in 3a is 10%, i.e., beginning to be comparable to the uncertainty in 12C(a,g)16O .Error in one rate compromises the accuracy of the other West, Heger, and Austin (2013 in press) astroph 1212.5513

West, Heger, and Austin (2013)

3a uncertainty dominated by pair width of 0+ resonance

22Ne(a,n)25Mg and the Heaviest Supernova

14N(a,g)18O(a,g)22Ne(a,n)25Mg

22Ne burns at the very end of helium burning. If it does notburn to completion or if it burns by 22Ne(a,g)26Mg,then the neutrons are released later in carbon burning when there are abundant neutron poisons like 23Na.

The s-process is thus stronger in stars that reach higher temperature in helium burning, i.e., in more massive stars.

The production of the s-process relative to 16O thus dependson the mass of the star. Only the most massive stars make it.

Smartt, 2009ARAA

Progenitors heavier than 20

solar masses excluded at the 95% condidence

level.

Presupernova stars – Type IIp and II-L

The solid line is for a Salpeter IMF with a maximum mass of 16.5solar masses. The dashed line is a Salpeter IMF with a maximum of 35 solar masses

LOW

Brown and Woosley (2013, submitted)

Brown and Woosley (2013, submitted)

22Ne(a,g)26Mg 22Ne(a,n)25Mg

Longland, Iliadis, and Karakis (PRC, 2012)

norm hi x 2

Radioactivities Detected by their Gamma-Ray Lines

Radioactivity Lifetime Detected Produced

44Ti 89 y 87A, Cas A, Tycho?

Explosive Si burning

26Al 1.04 x 106 ISM Explosive Ne burning

60Fe 3.8 x 106 ISM Explosive He burning

Reactions affecting 44Ti(a-rich freeze out)

Relevant temperaturerange T9 = 2 - 4

40Ca(a,g)44Ti

Nassar (2006) Vockenhuber (2008) Hoffman et al (2010) Robertson et al (2012)

Considerable variation, esp.H10 vs R12, error ~ 25 - 50%. Hauser Feshbach not reliable.

44Ti(a,p)47V

Sonzogni et al (2000)

re-evaluatedHoffman et al (2010)

radioactive beam at TRIUMF (DRAGON)

Summary:

40Ca(a,g)44Ti and 44Ti(a,p)47Sc are most critical. The formeris now better known thanks to Robertson et al but given the dispersion on past measurements further study maybe warranted. The latter is still uncertain to about a factor of two or three for the relevant temperature range.

The error in rates could compensate for most of the discrepancy between models and the observedsignal without invoking unusual explosion geometry – Hoffman et al (2010)

INTEGRAL OBSERVATIONS OF 26Al (t1/2 = 0.72 My AND 60Fe (t1/2 = 1.5 - 2.6 My) IN THE ISM

Brightness Ratio = 0.15 +- 0.04Necessary mass ratio = (0.15)(60/26) = 0.35

26Al (32 sigma signal) 60Fe (5 sigma signal)

Target 0.35

Timmes, Woosley and Weaver (1995) 0.36 (prediction)

Woosley and Heger (2007) new rates and opacities and mass loss 1.8

Woosley and Heger (2007) adjusting only 26Al cross sections using experiment rather than HF 0.95

further changes in 59,60Fe and 22Ne(a,n) could reduce it by as much as 2 0.50??

Meynet, Palacios, Limongi, Chieffi additional effects due to treatment of rotational mixing, convective algorithm, metallicity, mass loss, and IMF.

60Fe

60Fe(n,g)61Fe 30 keV 9.9 +- 1.4 +- 2.8 mbmeasured by activation. Answer sensitive to uncertain t1/2(60Fe)Uberseder et al, PRL, 102, 1101 (2009)

59Fe(n,g)60Fe (t1/2 = 44.5 d)being studied by photodissociation of 60Fe at GSIUberseder PhD thesis (Notre Dame) just completed. Paper in preparation – “ will be submitted in a few weeks”No big surprises

The production of 60Fe is most sensitive to 59Fe(n,g)

60Fe target 7.8 x 1015 atoms - Schumann et al (NIMPA 2010) - chemical extraction from accelerator waste-

60Fe

26Al is produced both by hot hydrogen burning (and is enhanced in massive star winds) and supernova explosionsby explosive neon burning.

26Al (n,p)26Mg and 26Al(n,a)23Na in progress at TRIUMF and LANSCE by Buchmann et al. Target fabrication at TRIUMF. Pulsed neutron measurements at LANL.

Will narrow uncertainty but corrections for isomericstate (228 keV) will remain uncertain. Some information from reverse reactions.

26Al

CONCLUSIONS

• A time of rapid progress in laboratory nuclear astrophysics. Key reaction rates near the valley of beta-stability are finally within grasp to the desired accuracy

• A major frontier now is radioactive beamsand targets

• Bridging the laboratory and theoretical modelswith refereed nuclear data archives is an essential and very cost effective activity