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Numerical Simulations of Merging Black Holes and Neutron Stars Francois Foucart (LBNL, Einstein Fellow) SxS Collaboration Einstein Fellows Symposium Oct 19th 2016
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Page 1: Numerical Simulations of Merging Black Holes and …asc.harvard.edu/fellows/symp_presentations/2016/Foucart...Numerical Simulations of Merging Black Holes and Neutron Stars Francois

Numerical Simulations of Merging Black Holes and Neutron Stars

Francois Foucart (LBNL, Einstein Fellow) SxS Collaboration

Einstein Fellows Symposium Oct 19th 2016

Page 2: Numerical Simulations of Merging Black Holes and …asc.harvard.edu/fellows/symp_presentations/2016/Foucart...Numerical Simulations of Merging Black Holes and Neutron Stars Francois

Gravitational Waves

Short Gamma-ray bursts

r-process / IR transients

Image: Korobkin et al. 2012

Neutron Star Mergers : Extreme Astrophysical Laboratories

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What can we learn from mergers?

Gravitational Waves: Test General Relativity

Measure NS/BH mass & spin distributions Constrain nuclear physics through NS equation of state

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Image: Lackey & Wade 2015, see also Del’Pozzo et al. 2013

Finite size effects: inspiral

Tides in neutron stars cause large stars to merge faster!

1 yr of `typical’ LIGO data ➡

Radii measured to ~10%

Important caveat:Assumes perfect waveform model

BH-BH vs BH-NS merger

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Inspiral models: Current status

Hinderer, ..FF et al. 2016

Build semi-analytical model (e.g. Effective One Body)

Perform high-accuracy numerical simulations

Calibrate model parameters

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EM signals (SGRB, kilonova): Demonstrate origin of SGRBs

Estimate contributions to r-process elements production Merger environment: host galaxy, ISM density Independent constraints on NS/BH properties

BH-NS

No post-merger EM signals Potential post-merger EM signals

What can we learn from mergers?

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Types of merger ejecta and neutrino effects

Tidal EjectaCold, mostly neutrons

Favored by: Large stars

Asymmetric mergers

Shocked EjectaHot, less neutrons Only for NS-NS

Favors small radii

Post-Merger Disks: Winds (B-fields, ν)

Strong ν effects

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Neutron rich (Ye<0.25) : produce heavy r-process elements (A~120-210) [IR transient]

Otherwise : produce lower mass r-process elements (A~90) [Optical transient]

Dynamical ejecta: Always neutron rich (Ye ~ 0.05) Shocked ejecta / wind: Neutrino absorption drive Ye up

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N

From simulations to observables:

Full GR simulations Long disk

evolutions (fixed metric)

Outflow models

Light curves (3D radiation

transport)

r-process (nuclear reaction network)Critical improvement:

Realism of simulations

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Conclusions

• Wide range of physical effects can be studied through BH-NS / NS-NS mergers

• Merger dynamics and outcome can only be studied with general relativistic simulations

• Good qualitative understanding of merger dynamics

• Improving waveform models for NS, still need to reduce systematics for upcoming LIGO detections

• Post-merger evolution requires detailed, complex microphysics, and is still work in progress


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