nuclear masses and the site ofr-process nucleosynthesis
Rebecca Surman
University of Notre Dame
Hirschegg 2017

Neutron star mergers:
From gravitational waves
to nucleosynthesis

Hirschegg, Austria
17 Jan 2017

r-process nucleosynthesis
solar systemr-processresiduals

Arnould+2007

β(n, γ )(γ ,n)€€

r-process nucleosynthesis
solar systemr-processresiduals
Cowan+2011

Arnould+2007

elemental abundancesfrom r-processenhanced metal-poor
halo stars

r-process astrophysical site: BNS/NSBH mergers?
astrophysical modeling of BNS/NSBH mergers
talks by A Bauswein, S Rosswog, M Wu, T Piranelectromagnetic transient: macronova/kilonova
talks by J Barnes, R Wollaeger

gravitational waves from merger events
talks by B Sathyaprakash, S Rosswog

r-process elements in low metallicity stars
talks by A Frebel, T Hansen, C Hansen

galactic chemical evolution studies
talks by F Matteucci, T Kajino

neutrino physics of merger events

talks by G McLaughlin, H Yasin, M Wu

r-process abundance pattern signatures
very neutron richfission cycling

barely neutron richlimit seed production

r-process simulations: required nuclear data
massesbeta-decay rates
beta-delayed neutron emission probabilities
neutron capture rates
fission rates
fission product distributions
neutrino interaction rates

r-process simulations: required nuclear data
massesbeta-decay rates
beta-delayed neutron emission probabilities
neutron capture rates
fission rates
fission product distributions
neutrino interaction rates

see talks by
J Engel, S Nishimura

figure by M Mumpowerr-process simulations: required nuclear data
massesbeta-decay rates
beta-delayed neutron emission probabilities
neutron capture rates
fission rates
fission product distributions
neutrino interaction rates

see talk by K Blaum

figure by M Mumpowerr-process simulations: required nuclear data
massesbeta-decay rates
beta-delayed neutron emission probabilities
neutron capture rates
fission rates
fission product distributions
neutrino interaction rates

figure by M Mumpowerr-process simulations: required nuclear data
massesbeta-decay rates
beta-delayed neutron emission probabilities
neutron capture rates
fission rates
fission product distributions
neutrino interaction rates

see talks by L Atar,M Eichler, S Giuliani

figure by M Mumpowerr-process simulations: required nuclear datamasses
beta-decay rates
beta-delayed neutron emission probabilities
neutron capture rates
fission rates
fission product distributions
neutrino interaction rates

sensitivity study review:
Mumpower, Surman, McLaughlin, Aprahamian
Progress in Particle and Nuclear Physics 86 (2016) 86
figure by M Mumpowerthe rare earth peakIts formation mechanism issensitive to both theastrophysical conditions of thelate phase of the r-process
and the nuclear physics of thenuclei populated at this time

N=82

rare earth peak

N=126

Surman, Engel, Bennett, Meyer 1997

rare earth peak formation

FRDM

Mumpower, McLaughlin, Surman 2012

HFB-21

exhausted, depending on the expansion time scales. Wh
sent an unexpected doubly asymmetric fission
the neutron density drops below some 1020 cm"3 , the tim
a characteristic four-hump pattern, as illustrated
scale of neutron capture becomes longer than a few seearthpeak
Suchrarefragment
distributions
have formation
never been
onds, and the nuclear flow is dominated by ! decays baxperimentally and can be traced back to theto the stability line (as well as fission and " decay for t
potential energies at large deformations ofheaviest species). The final abundance distribution of t-rich fragments favored by the A ’ 278 fission.
3 $ 10"3 M% of ejecta during the NSM is compared wi
ymmetric fission modes can also be seen on thethe Solar System composition in Fig. 4. The similari
nergy surface (Fig. 3) obtained from a detailed
between the solar abundance pattern and the prediction
c calculation [50] for 278 Cf in the deformationthe 140 & A & 180 region is remarkable and strong^^elongation hQ20 i, asymmetry hQ30 i). This calsuggests that this pattern constitutes the standard signatu
es a state-of-the-art mean-field model with theof r processing under fission conditions.
raction. The two fission valleys indicated byig. 3 lead to asymmetries similar to the distriesented in Fig. 2 obtained with SPY. The
100-3
Solar
Goriely+13 10FRDM

Mass fraction

10-1

1010-4-2

140

10-3

150

160

170

180

HFB-2110-4

Mumpower, McLaughlin, Surman 2012

80100

120

140

160

A180200220240

rare earth peak formation

Mumpower, McLaughlin, Surman, Steiner, JPhys G, acceptedrare earth peak formation

Neodymium (Z = 60) isotopic chain

Mumpower, McLaughlin, Surman, Steiner, JPhys G, acceptedAs expected the abundance pattern shows no feature in
histhe rare earth region. This suggests the DZ mass model
thereverse-engineering the rare earth masses
is missing the ingredient that leads to dynamical raremes
earth peak formation.
hotSince we have a baseline model without structure inthethe rare earth region we are free to determine the missing
erycomponent of the mass model which is required to match
tothe r-process residuals. Previous studies have suggested
that a kink in the separation energies as a function ofreneutron number is required [38, 39], but we wish to startical
with as little preconceived notion as possible about whatosethis structure should be. Therefore, instead of choosthe
ing a parameterized form for a kink structure, we let anTo
additional mass term float freely in neutron number, N :mass modification parameterization:eu(Z C)2 /2fset
M (Z, N ) = MDZ (Z, N ) + aN e(1)nditheHere,M (Z, N ) is the new mass generated from the baseMumpower, McLaughlin, Surman, Steiner, JPhys G, acceptedreverse-engineering the rare earth masses
hot, (n,γ)-(γ,n) equilibrium

cold, very neutron-rich

Mumpower, McLaughlin, Surman, Steiner, JPhys G, acceptedrare earth peak formation comparison

hot, (n,γ)-(γ,n) equilibrium

cold, very neutron-rich

Mumpower, McLaughlin, Surman, Steiner ApJ 2016

predicted mass surfaces
hot, (n,γ)-(γ,n) equilibrium
persistent feature,single
astrophysicaltrajectorycold, very neutron-rich

Neodymium (Z = 60) isotopic chain
Mumpower, McLaughlin, Surman, Steiner, JPhys G, acceptedpredicted mass surfaces
hot, (n,γ)-(γ,n) equilibrium
persistent feature,
multiple
astrophysicaltrajectories

cold, very neutron-rich

Neodymium (Z = 60) isotopic chain
Mumpower, McLaughlin, Surman, Steiner, JPhys G, acceptedpredicted mass surfaces
hot, (n,γ)-(γ,n) equilibrium
localized feature,
multiple
astrophysicaltrajectories

cold, very neutron-rich

Neodymium (Z = 60) isotopic chain
Mumpower, McLaughlin, Surman, Steiner, JPhys G, accepteduncertainties in nuclear masses

Mumpower, Surman, Fang, Beard, Aprahamian 2016

systematic uncertainties in nuclear masses:
impact on r-process simulations

Surman, Mumpower, McLaughlin 2016
masses from massexplorer.frib.msu.edu: Olsen, Nazarewicz:

see also Martin+2016

SKM*
SKP-3
SLY4SV-MIN
UNEDF0
UNEDF1

uncertainties innuclear masses

MC variations
ΔM=MFRDM-MAME

Surman, Mumpower,Aprahamian 2016

MC variations
ΔSN=SN,max-SN,minrandom uncorrelated uncertainties in masses:
impact on r-process simulations

Surman, Mumpower, McLaughlin 2016
FRDM masses + Monte Carlo variations within mass model rms (~0.5 MeV)

impact of upcoming
measurements
2012 AME+ extrapolated+ FRIB reach

Surman, Mumpower,Aprahamian 2016

summary
The role of compact object mergers in the synthesis of the heaviest
elements is under investigation from many directions

One such avenue is through nuclear physics, where current and nextgeneration radioactive beam facilities
will continue
to pushThe
Numberof theIsotopes Ava
boundaries of our knowledge of extremely neutron-rich nuclei at FRIB
As nuclear physics uncertainties
are reduced, we can exploit
details of the r-process
abundance pattern, such as therare earth peak, to explore thenature of the r-process site!

!

!
figure from B Sherrill