Kilonova signatures and the r -process FRIB and the GW170817 - - PowerPoint PPT Presentation
Kilonova signatures and the r -process FRIB and the GW170817 kilonova Jennifer Barnes NASA Einstein Fellow Columbia University mergers: a stellar danse macabre final few orbits: strong GW source Image: NASA e.g. Lattimer & Schramm 1974,
FRIB and the GW170817 kilonova
Jennifer Barnes NASA Einstein Fellow Columbia University
final few orbits: strong GW source
Image credit: Daniel Price (U/Exeter) and Stephan Rosswog (Int. U/Bremen)
Image: NASA
e.g. Lattimer & Schramm 1974, 1976 Li & Paczynski 1998
final few orbits: strong GW source
Image credit: Daniel Price (U/Exeter) and Stephan Rosswog (Int. U/Bremen)
merger: neutron star is partially disrupted, central remnant forms
Image: NASA
e.g. Lattimer & Schramm 1974, 1976 Li & Paczynski 1998
final few orbits: strong GW source
Image credit: Daniel Price (U/Exeter) and Stephan Rosswog (Int. U/Bremen)
ejecta: some material is escapes; some is bound merger: neutron star is partially disrupted, central remnant forms
Image: NASA
e.g. Lattimer & Schramm 1974, 1976 Li & Paczynski 1998
final few orbits: strong GW source
Image credit: Daniel Price (U/Exeter) and Stephan Rosswog (Int. U/Bremen)
ejecta: some material is escapes; some is bound final: a central NS or BH, an accretion disk, unbound ejecta merger: neutron star is partially disrupted, central remnant forms
Image: NASA
e.g. Lattimer & Schramm 1974, 1976 Li & Paczynski 1998
“kilonova”
material
synthesized An expanding cloud heated by radioactive decays
X-ray UV Optical IR Radio
t-tc (days)
10-2 10-1 101 100
transient source detected in galaxy NGC 4993 Let’s zoom in
X-ray UV Optical IR Radio
t-tc (days)
10-2 10-1 101 100
transient source detected in galaxy NGC 4993 Let’s zoom in
days since merger Villar+17 log10 luminosity
0 5 10 15 20 25 30
+
∝
time ergs/s
˙ Erad(t)
Energy from radioactivity
(bolometric) light curves
time ergs/s
˙ Erad(t)
Energy from radioactivity Efficiency of thermalization
(bolometric) light curves
time ergs/s
˙ Erad(t)
Energy from radioactivity Efficiency of thermalization Opacity (composition) sets the diffusion time/ time for the ejecta to become optically thin
(bolometric) light curves
time ergs/s
˙ Erad(t)
Energy from radioactivity Efficiency of thermalization Opacity (composition) sets the diffusion time/ time for the ejecta to become optically thin
(bolometric) light curves colors & spectra
temperature set by the net effect of radioactivity, thermalization, photon absorption/ emission, and cooling
affect the spectrum
correspond to particular atoms or ions
˙ Erad(t) = fc2 t
The expression
Roberts+2011
Beta decay Fission Total
Metzger+2010 erg g-1 s-1 erg g-1 s-1 log (days) log (days)
The basic behavior has since been borne out by nuclear network calculations
behavior may break down at late times. was first derived analytically (Li & Paczyński 1998; see also Hotokezaka+17)
The r-process produces elements with atomic structures that are unique among explosively-synthesized compositions.
Lanthanides Actinides
SNe mergers
Elements made by the r-process
photon wavelength cross section
photon
absorption if ∆E ≈ hc
λ
=
κexp(λc) = 1 ρctexp X
i
λi ∆λc
τ = πe2 mecfoscn1texpλ0 Sobolev optical depth sets interaction probability with a particular line The expansion opacity determines the effective continuum opacity
d-block elements Lanthanides
Kasen, Badnell, & JB 2013 bound-bound expansion opacity (cm2 g-1)
102 101 10-5 10-4 10-3 10-2 10-1 100 5,000 10,000 15,000 20,000 25,000
angstroms
FeII (Z = 26) CeII (Z = 58) NdII (Z = 60) OsII (Z = 76)
T = 5000 K rho = 10-14 g cm-3
JB & Kasen 2013
many-body Quantum Mechanical system lines, levels,
strengths synthetic
The r-process produces elements with atomic structures that are unique among explosively-synthesized compositions.
p-shell (6 e-) f-shell (14 e-) s-shell (2 e-)
Lanthanides Actinides
SNe mergers
Nlines ≈ N 2
lev
Nlev ≈ g! n!(g − n)!
n =
g = 2(2l + 1)
Simple analytic estimates:
d-shell (10 e-)
tdiff ≈ ✓Mκ vc ◆1/2
diffusion time: adiabatic losses: Ephot ∼ t−1 line blanketing at optical wavelengths
0 2 4 6 8 10
days since merger
0.5 1.0 1.5 2.0 2.5 3.0
bolometric light curve spectrum at 4.5 days
microns
Xlan = 10−5 Xlan = 10−4 Xlan = 10−2 Xlan = 10−1
42 41 40
log10 Luminosity
2.0 1.5 1.0 0.5
flux
Kasen, Metzger, JB+17 more heavy r-process
Lippuner & Roberts 2015
Fe-group elements light r-process heavy r-process fewer free n per seed more free n per seed
Ye = p p + n
Lippuner & Roberts 2015
Fe-group elements light r-process heavy r-process fewer free n per seed more free n per seed
Ye = p p + n
more weak interactions fewer weak interactions
Lippuner & Roberts 2015
Fe-group elements light r-process heavy r-process fewer free n per seed more free n per seed
Ye = p p + n
more weak interactions fewer weak interactions
dynamically squeezed tidally stripped disk
time ergs/s
Radioactive energy converted to thermal photons
˙ Etherm
˙ Erad(t)
Energy from radioactivity
(bolometric) light curves
time ergs/s
Radioactive energy converted to thermal photons
˙ Etherm
thermalization efficiency depends on:
sections)
˙ Erad(t)
Energy from radioactivity
(bolometric) light curves
α-decay
5 10 15 20 25 30 Days 0.0 0.2 0.4 0.6 0.8 1.0 f (t) fission fragments β-particles α-particles γ-rays
Thermalization efficiencies per particle
β
β ν γ
fission fragments
Fissioning or -decaying nuclei with weeks or months could substantially affect the luminosity
100 10-1 10-2 10-3 10-4 10-5 102 103 104 105 106 107
log10 (time)
data courtesy Y. Zhu
Fraction of energy in each channel Californium-254
τ1/2 = 60.5 QSF ≈ 200 days
MeV
Fissioning or -decaying nuclei with weeks or months could substantially affect the luminosity
heating (ergs s-1 g-1) log10 days
Zhu+2018
Energy Released
absolute magnitude time (days)
Light Curves Observed
Zhu+2018
Late-time light curves can probe the production of the heaviest nuclei and give more detailed information about the composition