Dynamical Ejecta from
Binary Neutron Star Mergers
David Radice1
1
Walter Burke Fellow
Collaborators: S. Bernuzzi, F. Galeazzi, J. Lippuner, P. Mösta,
L. Roberts, C. D. Ott, L. Rezzolla
Background
t
t0 = 0.02 ms
t
t0 = 2.58 ms
t
t0 = 10.10 ms
1015
1014
200
y [km]
1012
1011
0
1010
109
108
200
107
200
•
•
0
x [km]
200
200
0
x [km]
200
200
0
x [km]
200
Dynamical ejecta: outflow during merger
Consequences: nucleosynthesis? EM counterparts?
See also talks by Dietrich, Branchesi, Metzger
106
⇢ [g cm 3 ]
1013
Open Questions
• Ejection: tides or shocks?
• Composition, morphology?
• Impact of weak reactions? EOS?
• NSNS mergers: the origin of r-process elements?
Methods: WhiskyTHC
• GRHD: MP5+HLLE
• Gravity: BSSN or Z4c
• Tabulated nuclear EOS
• Neutrino cooling and heating
THC = Templated Hydrodynamics Code
Ejection Mechanisms
EOS : LS220
M = 1.38 M
Impact of Weak Interactions
M/Mej
100
10
10
10
HY QC
LK QC
M0 QC
1
2
M = 1.38 M
Relative abundances
EOS : LS220
10
1
10
2
10
3
10
4
10
5
Solar
HY QC
LK QC
M0 QC
3
0.08
0.16
0.24
Ye
0.32
0.40
50
100
150
A
• The yields are robust for A > 120
• A < 120: needs Ye > 0.25, critical role of neutrinos
200
Outflow Morphology
EOS : LS220
HY QC
LK QC
M0 QC
1
10
2
10
3
M/Mej
M/Mej
10
M = 1.38 M
0
22.5
45
✓
67.5
90
10
1
10
2
10
3
0.01
HY QC
LK QC
M0 QC
0.17
0.33
v1 [c]
• Ejecta mostly contained within 600 of orbital plane
• Mildly relativistic velocities
0.49
Impact of Equation of State
EOS : DD2, LS220, SFHo M = 1.35 M
1
M/Mej
10
DD2
LS220
SFHo
10
10
2
Relative abundances
100
10
1
10
2
10
3
10
4
10
5
Solar
DD2
LS220
SFHo
3
0.08
0.16
0.24
Ye
0.32
0.40
50
100
150
200
A
• EOS impacts composition and mass
• The yields for A > 120 are robust;1st peak underproduced
Total Ejected Mass
EOS : SFHo
Simulation
WhiskyTHC
Palenzuela+ 2015
Bauswein+ 2013
Sekiguchi+ 2015
Sekiguchi+ 2015
M = 1.35 M
Cooling
x
x
x
x
Heating
x
Ejecta Mass [Msun]
3.5 x 10-3
3.2 x 10-3
4.8 x 10-3
10.0 x 10-3
11.0 x 10-3
Large uncertainty in the ejecta mass!
Conclusions
• Outflows driven by tidal torques, shocks, and
neutrino radiation
• Robustly produce 2nd and 3rd peak r-process
elements; 1st peak still unclear
• Still some work do to (better HD, radiation, MHD,
disk winds, …)
Impact of Orbital Dynamics
EOS : LS220
M = 1.38 M
Mej [M ]
100
10
1
10
2
10
3
10
4
10
5
10
6
10
7
HY QC
LK QC
M0 QC
HY RPX
LK RPX
M0 RPX
0.0
5.0
7.5 10.0
rp /M
15.0
• Neutrino cooling decreases ejecta mass by ~1/2
• Eccentric mergers can eject significantly more mass