The r-process and kilonova
observables
Jennifer Barnes
Hirschegg Workshop
January 18, 2017

Credit: Koppitz & Rezzolla

Roadmap• Kilonova 101• background• early models• Progress and uncertainties• r-process opacities (color)• thermalization (luminosity)

Credit: Baiotti, Giacamazzo & Rezzolla

EM Counterparts
radioactive transientsshortGRB

GRB
afterglow

neutronprecursor

tidally
stripped

tm + few s

tm + few s

tm + ~hourradioafterglow

kilonova

dynamicallysqueezed

tm + days

diskoutflows

tm + months

EM counterparts: kilonovae
mini-supernova
powered by radioactive
decay in the dynamicalejecta and disk winds• isotropic• timescales of days toweeks

Credit: Baiotti, Giacamazzo & Rezzolla

kilonovae offer us awindow into heavy
element production via
the r-process
origin of the heavy
elements

EM counterparts: kilonovae
mini-supernova
powered by radioactive
decay in the dynamicalejecta and disk winds• isotropic• timescales of days toweeks

Credit: Baiotti, Giacamazzo & Rezzolla

kilonovae offer us awindow into heavy
element production via
the r-process
origin of the heavyelementsr-process origins
Compact Object Mergers
naturally produce
low-entropy, neutronrich conditions• rare (?), but prolific• time delay•

Core Collapse SNe( ⌫ -driven winds)
r-process abundancein old stars• skimpy r-process, butcommon• high-entropy, low
dynamical timehinders production ofseed nuclei•

Kilonovae: early models
Lattimer and Schramm 1974, 1976
Li & Paczynski 1998, Kulkarni 2005
Metzger et al. 2010, Roberts et al. 2011

Monte Carloradiation
tp ' 1 dayEmission
peaks
in V-bandtransport,taking41
1Powered TransientsRadioactivelyfromCompact
ObjectMergers
9Lbol,p . 5 ⇥ 10 ergs srp = F e(e.g. Metzger et al. 2010)

Figure 4. Bolometric light curve of the radioactively-poweredtransients from NS-NS/NS-BH mergers, calculated assuming a to−2

Metzger et al. 2010

Figure 5. Top Panel: νLν color light curves from the ϵtherm = 1
calculation in Figure 4. V−, U−, and R− band light curves are

The r-process: challenges
Endgame: determine ejected mass, composition from data
Obstacles: unusual nucleosynthesis with limited
experimental measurementsopticalproperties of the
r-process-richejectacolor andluminosity

r-process energy
generation andthermalization
efficiency

luminosity, light
curve shapeThe r-process: challenges
Endgame: determine ejected mass, composition from data
Obstacles: unusual nucleosynthesis with limited
experimental measurements
opticalproperties of the
r-process-richejectacolor andluminosity

r-process energy
generation andthermalization
efficiency

luminosity, light
curve shapeExpansion opacity
Sobolev optical depth:
220⇡e
⌧i =
f Nl
me cc✓

1Nu g lNl g u◆⇥ctexp
0Expansion opacity (e.g Karp 1977, Eastman & Pinto 1993)
1 X
exp =⇢ctexpii

1e ⌧icAssumes line profiles widths are small and that stronglines do not overlap in wavelength spacecross section

Kilonovae: opacity

photonwavelength
Lanthanides

Iron Groupvalanceshellstructure
open d-shell

open f-shell

Kilonovae: opacity
bound-bound opacity (lines) is a function of atomic structure:
more valence e-more lines

higher 

open f-shell

open d-shell
Kasen, Badnell, & JB 2013

opacity

observables

composition

shine blue or glow red?

10Bolometric Luminosity

42Fer-process

Iron opacities
r-process opacities

8Kasen, Badnell & JB 2013

IronT ~ 6000K

61041

1041
ergs s-1

Spectrarelative flux

Luminosity (ergs s 1 )1042

The Astrophysical Journal, 774:25 (13pp), 2013 September 1101040

4r-process
T ~ 2500K

40

210103939002244

JB & Kasen 2013
10126688 10121414
Days
days

00500

1000
1500
2000
3000
Figure 11. Synthetic spectra (2.5 days after mass ejection) of the r-process SNnanometersmodel described in the text,calculated using either Kurucz iron group opacities(black line) or our Autostructure-derived r-process opacities (red line). For
comparison, we overplot blackbody curves of temperature T = 6000 K (blackdashed) and T = 2500 K (red dashed). The inset shows the corresponding
bolometric light curves assuming iron (black) or r-process (red) opacities.
For comparison, we also plot a light curve calculated with a gray opacity ofopacity: multi-component light curves
r-process yields are not guaranteed!
Lippuner & Roberts 2015

I.G.E.sr-processopacity: multi-component light curves

Bolometric Luminosity

different ejection mechanisms + ⌫ -interactions⌫ -irradiated disk
wind (light rneutron-richprocess/I.G.E.’s
dynamicalejecta (heavyr-process)r-processNickel-like

BK13 (adapted)

TimeKilonovae: interactions
wind + dynamical ejecta

Kilonovae: interactions
wind + dynamical ejecta

The r-process: challenges
Endgame: determine ejected mass, composition from data
Obstacles: unusual nucleosynthesis with limited
experimental measurements
opticalproperties of ther-process-richejectacolor andluminosity

r-process energygeneration andthermalization
efficiency

luminosity, light
curve shapeThe r-process: challenges
Endgame: determine ejected mass, composition from data
Obstacles: unusual nucleosynthesis with limited
experimental measurements
opticalproperties of the
r-process-richejectacolor andluminosity

r-process energy
generation andluminosity, lightwith Meng-Ru Wu, Gabriel Martinez-Pinedo
thermalization
curve shapeefficiency

Thermalization in kilonova
radioactive decay

Thermalization in kilonova
radioactive decaytransfer to thethermal poolThermalization in kilonova
re-radiated asthermal emission
sn2001b
flux

radioactive decaytransfer to thethermal pool

wavelengthThermalization in kilonova
radioactive decaytransfer to thethermal poolre-radiated asthermal emission
flux

sn2001b

wavelength

Challenges:
1. Exotic composition with unknown cross-sections
2. Multiple decay chains generating , ↵, - and xrays, and fission fragments, each at distinct, often
unknown, rates and energies
3. Uncertainties in ejecta parameters

Thermalization: methods
nuclear reaction networks todetermine r-process yields

Thermalization: methods
nuclear reaction networks todetermine r-process yields
cross sections
for energy loss

decay modes
and spectra

ejecta+parameters

Thermalization: methods
nuclear reaction networks todetermine r-process yields
cross sections
for energy loss

decay modes
and spectratransport code

ejecta+parameters

Thermalization: methods
nuclear reaction networks todetermine r-process yields
cross sections
for energy loss

decay modes
and spectratransport code

ejecta+parameters

thermalization efficiency(per particle)+
energy generation
fractionsThermalization: methods
nuclear reaction networks todetermine r-process yields
cross sections
for energy loss

decay modes
and spectratransport code

ejecta+parameters

thermalization efficiency(per particle)+Ėabs (t)ftot (t) =Ėrad (t)energy generation
fractionsCase study:-particles
1.6

Energy-loss
channels:• Bethe-Bloch• Plasma losses• Bremsstrahlung

1.4
day

b-spectra

1.2
1.0
0.8
0.6

Time-dependentf (t)• for a range ofejectaparameters

30
25
20
15
1050.41011

free eBethe-Bloch0.00.0Brems.
total1010

109
10 2

JB+1610 1
100
Energy (MeV)

101Mej = 0.005M

JB+160.5

1.0 1.5 2.0
Energy (MeV)

2.5

Mej = 0.05M

3.0Time-dependent
spectra• from r-process
yields andnuclear data

1.00.8f b (t)Ė/r (MeV s 1 cm3 g 1 )

0.2

0.6
0.4
0.2

JB+16
0.0
05 10

15 20
Days

2530

Energy-generation rates

Fraction of energy
fraction of energy

100

DZ31
FRDM

HFB21
WS3-decay↵-decay

10 1b-decay
a-decay
total fission
10 2-510 1fission-4 total-3-2 -1 a-decay
0 1log (time)

fission2Thermalization: effect on light curves
lower luminosity (especially for less massive ejecta)• allows more better estimate of mass from observations•1041

fiducial model

1040

JB+16Lbol (ergs s 1)

1039
1038
JB+16

1037

heavy model

1041
1040
1039

g transport only
f tot = f tot (t)

1038
1037
05

1015 20
Days

25

30

application to kn (?)
associated with 130603B(Berger+ 13, Tanvir+ 13)

Footnote: the role of ↵ -decay
Not all decay modes thermalize equally: thermalization ismore efficient for compositions where ↵-decay and fission
are importantfission fragments

1.0b-particles
a-particles
g-rays

0.8f (t)-decay
35%

40%

25%

0.6
0.4
0.2
0.0

100%
051015Days

202530JB+16↵ -decayLbol (ergs s 1)

Footnote: the role of ↵ -decay
FRDM
DZ311040

1039

JB+1638
1005

1015Days202530Luminosity (especially at late times) could indicate theimportance of -decay (or of fission!)↵