超新星爆発および中性子星合体における r プロセス元素合成
r-process nulceosynthesis: supernovae vs. neutron-star mergers	
Shinya Wanajo (TUM/MPA)
K. Nomoto (IPMU), H.-T. Janka, B. Müller, A. Bauswein (MPA)
T. Tachibana (Waseda), S. Goriely (ULB)
素核宇融合による計算基礎物理学の進展 - ミクロとマクロのかけ橋の構築 –	December 3-5, 2011,合歓の郷		SN	  seminar	Shinya	  Wanajo	1	

origin of elements beyond iron	understood (big bang, cosmic rays, stellar evolutions, supernovae)	

not understood	

not fully understood, in particular noble metal, rare earth, actinide	SN	  seminar	Shinya	  Wanajo	

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recipe to calculate nucleosynthesis	
reaction channels for the i-th isotope v numerical computations using aZA

nuclear reaction network code(e.g., ~8000 isotopes and(_, n) (_, a)~100,000 reactions for r-process)(p, n)v experimental (whenever(p,a)`available) or theoretical
reaction rates(a, n)
i(n, a)(compilations available from,e.g., REACLIB, BRUSLIB)(n, p)(a, p) +v ρ and T temporal evolutions` , ecfrom astrophysical modeling(e.g., of supernova explosions orNA(a, _) (n, _)neutron-star mergers)
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SUPERNOVAE	

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6	how to cook gold and heavier	SN	  seminar	Shinya	  Wanajo	v either of the following isneeded to obtainn/seed > A(3rd) – A(seed)~ 100v high entropy
Srad (∝ T 3/ρ) > 200 kB/nuc
to slow the ααn ratev short expansion timescaleτexp < 10 ms
to slow the ααn ratev low electron fraction(protons per nucleon)
Ye < 0.2to leave free neutrons7	SN neutrino-driven wind	
Woosley et al. 1994	

“As a caveat, however, we note that
this agreement may be too good.”by the authors	v successful r-process in the neutrino-driven winds of Srad~400 kB/nuc(1D hydro, 20 M¤ star; Meyer+1992; Woosley+1994)v but such high entropy is unlikely(~100 kB/nuc; Takahashi+1994; Qian+1996; Otsuki+2000)
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neutrino-driven wind is “proton-rich”	
2D supernova simulation
Wanajo, Janka, Müller 2011	

self-consistent explosion of a 9 M¤ star
Hüdepohl+2009	−

νe + n → p + e

ν e + p → n + e+v Ye > 0.5 in all recent neutrino-transport simulations because ofsimilar neutrino energies and luminosities for all flavors (i.e., protons
are favored due to the p-n-mass diﬀerence)v but, early convective blobs have some n-rich pockets (< 10 M¤ only)
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10	supernovae at the low-mass end	Wanajo, Janka, Müller 2011	

Wanajo+2011	v 2D early convective ejecta:Ye, min ≈ 0.40 with
Srad ≈ 13 kB/nucv 1D ejecta: Ye, min ≈ 0.47 with
Srad ≈ 20 kB/nucSN	  seminar	v 2D: production of the 1st
peak 80Se and up to 90Zrv but of nuclei beyond N = 50v production factor of ~100
à ~ 4% of all SNe

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no n-rich ejecta from massive SNe !	

11M¤	15M¤	64

200.48 0.50 0.52 0.54 0.56 0.58 0.60 0.62
YeY-4ej= 0.499

4

6M [10 M6e, min

8Yej

-3

6M [10 Msun]

sun]

1015 Msun= 0.498

11 Msune, min

12200.48 0.50 0.52 0.54 0.56 0.58 0.60 0.62
Yev Ye, min ≈ 0.5 for self-consistent 2D SNe of 11, 15 M¤ (Müller+in prep)
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NEUTRON-STAR MERGERS	SN	  seminar	Shinya	  Wanajo	

13	NS mergers as another posibility	
www.mpa-garching.mpg.de	v coalescence of binary NSs
expected ~ 10 – 100 per Myr
in the Galaxy (also possible
sources of short GRB)v tidal ejection of n-rich matterwith Ye < 0.1(Goriely+2011)v neutrino- (or viscous, MHD)
winds from the BH accretion
torus with Ye ~ 0.2 – 0.4(Wanajo & Janka 2011)
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time [d]n-induced fission is faster than radiative neutron capture at
9 K by diamonds.

Fig. 3.— Time evolution of the total radioactive heating ratee.
per unit mass, hQi, mass number hAi, and temperature hT i (allmass-averaged over the ejecta) for the 1.35–1.35M (solid lines)
final mass-integrated ejecta composition is shownand 1.2–1.5M (dotted lines) NS mergers.
. 4. The A = 195 abundance peak related to= 126 shell closure is produced in solar distriThe AstrophysicalJournal
738:L32(6pp), 2011 September
10 all input
Goriely, Bauswein, & Jankan andfound tobe Letters,
almostinsensitive
toGoriely,
Bauswein, Janka 2011	
eters such as0.35
the initial abundances, the expansion
100
1.35–1.35MnuclearNS
1.35–1.35M NS
1.35–1.35M NS
ales, and the 0.3
adoptedmodels. In contrast,
1.35-1.35M NS-1Solar
10oeak around A = 140 originates exclusively from0.251.20-1.50MNSsion recycling, which takes place in the A ' 280–
-2o100.2
gion at the time
all neutrons have been captured.
nuclei are predicted
to fission symmetrically as vis0.15
10-3
Fig. 4 by the0.1A ' 140 peak corresponding to the10-4
symmetric fragment distribution. It is emphasized
0.05
gnificant uncertainties
still a↵ect the prediction of
10-50
probabilities andfragment distributions so that
0.25 0.32 0.39 0.46 0.53 0.60 0.68 0.015 0.021 0.027 0.033 0.039 0.045 0.051-0.4 0.2
0.81.4
2.0
2.6
0.35
10-6
act strength and1.20–1.50M
locationoftheA'140fission
NS
1.20–1.50M NS
1.20–1.50M NS
0.3 possible A = 165 bump observed(as well as the-710solar distribution)
depend on the adopted nuclear
0.25
050
100
150
200
250
.
A0.2
le most of the matter trajectories are subject to a0.15
y and temperature
history leading to the nuclear
ejectionof “pure”
n-matter;<<ejecta
0.1fromFig.
4.— Final nuclear
abundance
distributionsYofe the1.35–1.35M (squares) and 1.2–1.5M (diamonds) NS mergers as
nd abundance0.1distribution described above, somefunctionsof atomic mass.
The distributions
are normalized to thev
r-processwithfission
cyclyng:
elements can be
0.05 shock-heated at relatively low densolarr-abundance
distribution(dottedcircles).
Typically at ⇢0 > 1010 g/cm3 the Coulomb e↵ects
originof2.0 the“universality”?
0.25 0.34 distribution
0.44 0.53 0.63 0.72 0.82
0.015 0.025the0.035high0.045 0.055 0.065-1.0 -0.4
0.2
0.8
1.4
2.6
he NSE abundance
towards/ S
logSYeescaping in neutrinos is not considered) is plotted inegion (Goriely et al. 2011), but at lower densities,
Figure 1. Histograms of fractional mass distribution of the ejecta for the 1.35–1.35 M! NS merger (upperFig.
row) v
and3thebut
1.2–1.5both
Monly(lowerrow)
functions another! binarytheforand 1.2–1.5M
A1.35–1.35M>as 130;
source binais
gh temperatures
todensity
theρS photodissociationof allof density ρ (relative to thelead
saturation" 2.6 × 1014 g cm−3 ; left) and of electron
fraction Ye (middle) that the ejected matter had at its initial NS locationhQ(t)iandtheIn theaverage temperature evoluprior to merging. The right panels show the fractional mass distributions as functions of the final entropy S ries.
per nucleonWhilewhen the matterstarts its freeexpansion.
edium-mass
seed nuclei into neutrons and protons.
inset on the left panels the dots mark positions of mass elements that get ejected later. The locations are given in the projection
on the orbitalfor
plane at A
the time
needed<when130both NS-NS systems, thetion di↵er only slightly betweenthe stellar collision begins. may occur during the decompreson recombination(A color version of this figure
available in the online journal.)
SN	  siseminar	Shinya	  Wanajo	
16	 velociejecta
masses Mej and mass-averaged expansion
rovidedthe expansion
timescale of the trajectories
ties vexp di↵er considerably. While we find for the symg enough. For a non-negligible amount of ejected
metric system vexp ⇡ 0.31c (c being the speed of light)
ial, this recombination is indeed inefficient so that

NS mergers: dynamical components	ooo

Mass fraction
Mass fractionoMass fractionooSN	  seminar	Shinya	  Wanajo	

17	NS mergers: wind components	
Wanajo & Janka 2011	
0.6

Ye X_case 1case 2eY ,X

_0.4

0.2

semi-analytic wind modelv neutrino-driven wind fromthe BH-accretion torusv spherical PNS wind model isapplied with modifications
SN	  seminar	

0.0 11
10

10

910
T [K]

10

weak interactions on n and pv case 1: from T = 1 × 1010 Kv case 2: from T ≈ 6 × 1010 K(at the inner boundary)

Shinya	  Wanajo	

18	NS mergers: wind components	ejej

0.05

entropy	-310-40.110

9.0

9.5
10.0-1log u [cm s ]

2.0
2.5-1
log S [k10nuc ]10-3

100.1 10-4

1010-5

10

0.0 10-60
3.0

10-3-4-5-6

12log o [ms]3

Wanajo and Jankelectron fraction
at T = 2.5×109 K	

all
A > 100
A > 180case 1case 2ej

0.6ej

Δm /m

bulk of the wind ejecta has moderatev v ~ 0.1 cv S ~ 30 kB/nucv τ ~ 100 ms, andv Ye ~ 0.3 (case 2; but 0.2 in case 1)
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-2

B

0.8

-1

1010-5-6
0.010
10.5
1.5

log

0.2 10 timescale	

100.0010-2ej

ej

0.10

6m /m

ej

-2

velocity	 0.210

ej

0.15

00.3 10log linear-1106m /mlinear6m /m

000.310log linear
-1
10

0.4
0.2
0.0

0.1

0.2

Y

0.3

0.4

0.5e, 2.5

Shinya	  WFig.
anajo	
18.— Histogram of the ejecta-mass distribution ∆m19	ej (normalized by the total ejecta mass, mej ) for case 1 (solid lines) andfor case 2 (dotted lines) as functions of Ye,2.5 . Different colors correspond to all ejecta and those with all yields having A > 100 andrate oftic meris consi
betweelation s(at solaand of(2×10−(with iwe find130. Horate mlar r-p(Eq. (2It isof r-abon theThe tocan beNS mergers: wind components	
Wanajo &-2Janka 2011	
10
solar r-process abundance-2

10case 1 all D < 5 RS D < 3 R-3S-3

1010-4-4

10abundanceabundance

10-510-510-610-610-7-7

10

10

10-8
50

10-825050

100150200
mass numbercase 1 (extreme?)v Ye, min ~ 0.2v full (main) r-process
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solar r-process abundancecase 2 all D < 5 RS D < 3 RS

100150200
mass number

250

case 2 (reasonable?)v Ye, min ~ 0.3v weak r-process
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SMOKING GUN	SN	  seminar	Shinya	  Wanajo	

21	kilonova?	

electro-magnetic transients(macronova, Kulkarni 2005;kilonova, Metzger+2010)v heating from β-decay
and fission of r-productsv Lpeak ~ vexp1/2 Mej1/2~ 1041 – 1042 erg s-1v tpeak ~ vexp-1/2 Mej1/2~ hoursv absorption lines of
ton luminosities of the expanding NS merger ejecta caused by radioactive decay heating for the 1.35–1.35 M (solid lines) and 1.2–1.5 M (dashed. The upper, long-duration lines are the bolometric luminosities, the sequences of short-duration peaks correspond to the emission in the blue, visual,r-elements to beands (at wavelengths of 445, 551, 658 nm; from left to right).
on of this figure is available in the online journal.)
a “smoking gun”?

ysical Journal Letters, 738:L32 (6pp), 2011 September 10Goriely, Bauswein, & Janka

Goriely+2011	

d protons. Nucleon recombination may occur duringression provided the SN	  expansion
seminar	
timescale of the tralong enough. For a non-negligible amount of ejected
is recombination is indeed inefficient so that lightcluding D and 4 He) are also found in the ejecta!

!

We calculate an approximation of the light curves of such
events by employing
a semi-analytic,
simplified one-zone model
Shinya	  Wanajo	of Kulkarni (2005; see also Arnett 1982; Li & Paczyński 1998),
assuming that asymmetries of the emission remain modest(cf. Roberts et al. 2011). The EOS includes photons as well22	

with present and upcoming transient surveys if one assumes that
NS–NS/NS–BH mergers are the dominant r-process source. Notethat within the current uncertainties in Ṅmerge , current transient surveys should detect a few events per year if mergers are indeed thedominant source of the r-process, independent of M̄ej . In reality, thedetection efficiency for low M̄ej may be somewhat lower than this1/2simple estimate due to the shorter transient duration tpeak ∝ M ej
(equation 3).

estimate that the net thermalization efficiency is(Section 3.2).
(iv) For an ejecta mass M ej ∼ 10−2 to 10−3 M
transient that peaks on a time-scale ∼1 d at a boband luminosity ∼1042 erg s−1 (M B = −16) and ∼(MV = −15), respectively (Figs 4 and 5).
(v) We argue that the transition metal r-proce
likely to have UV absorption due to line blanketi
how nuclei).
can wekilonovae?
As finda result,
we predict that NS merge
Metzger+2010	
be relatively red (and redden in time; see Figs 5v follow-upof GW
diction not captured
by surveys
assuming single-temper
More LIGO/Virgo;
detailed models of the colour ebyemission.
advancedmerger transients will require
a better understan-1~ and6 –IR89
eventsspectrallines yrof second and third r-proces(Section 4.1). The presence of absorption lines(Kim+2005)
process elements is one ‘smoking gun’ predictiov follow-up
transients. of short GRBs
(vi) Because NS merger transients are isotropic,
given
the association withciple be detected in three independent ways: in cNS-NS/BH-NS
a detected GW source; mergers;
following a short-duration
blind optical/NIR transient
surveys.
GRB080503,
Perley+2009(vii) Given the low luminosities and rapid evolut
from NSmergers, their detection
will require clov blind
optical/NIR
surveys
between the GW and astronomical communities. G
byobservational
LSST/SASIR;
signature of kilonovae, the real-time f
detections
with sensitive, wide-field telescopes comostpromising?
Figure 7. Rates of detected kilonovae from NS–NS/NS–BH mergers witheffective sensitivity of LIGO/Virgo.
present and upcoming surveys as a function of the merger rate Ṅmerge (bot(viii) For an average ejecta mass M̄ej ≈ 10−2 Mtom axis) or the average ejecta mass M̄ej (top axis), calculated under theSN	  seminar	Shinya	  Wanajo	
23	veys such as PTF should ‘blindly’
detect ∼ one NS
assumptionthat NS–NS/NS–BH mergers are the primary sourceof r-processelements in the Galaxy. Also shown are the NS–NS merger rate estimates
per year if the merger rates lies at the high end of p(95 per cent confidence interval) from Kalogera et al. (2004).
LSST should detect ∼1000 yr−1 under the same askilonova?	

summary	v SNe are not very promising; NS mergers show some promise
but astrophysical models are still prematurev survey of kilonovae to be a smoking gun (with GWs, sGRBs)?
v key roles of computational physics include those of
nuclear physics (masses, n-capture, β-decay, fission, EOS, …)
astrophysical modeling (SNe and in particular NS mergers)
nucleosynthesis calculations of r-process including fission
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