Gravitational waves and neutrino emission from the merger of binary

neutron stars

Kenta KiuchiCollaboration with Y. Sekiguchi, K. Kyutoku, M. Shibata

Ref.) 1105.5035

IntroductionOur research target = high energy astrophysical phenomenae.g., Supernova energy ≈ 1.5*1046J = energy the Sun consumes for 1.2 trillion years !! SN1054 （ Crab Nebula）

r～ 1000km～ 10km

～ Solar mass

Energy source = gravitational potential energy ∝ r-1

Products of high energy astrophysical phenomena～ 10km ～ 3km（ 1 Solar

mass）

✓Density～ 1015g/cm3 　 (1.41 g/cm3) ⇒ General Relativity, Strong interaction

✓Temperature～ 1011K (15.7×106K)⇒ Weak interaction✓Magnetic fields～ 1015 Gauss (Sunspot： several

thousand Gauss)⇒Electromagnetic force

All of fundamental interaction play an essential role.

Physical aspects of high energy astrophysical phenomena✓Highly dynamical✓No special symmetry, e.g., spherical symmetry⇒Numerical modeling including four kinds of forces

Numerical RelativityFiguring out high energy astrophysical phenomena by numerically solving the Einstein equations

Importance of Numerical Relativity○ Gravitational waves✓imprinting “raw” information of sources✓extremely weak signal, hc 10∼ -22 = the change of (Size of H atoms)/(Distance to Sun)

GW detectorsNeed to prepare theoretical templates of GWs

Today’s topic = Coalescence of binary neutron stars✓Promising source of GWs✓Theoretical candidate of Short-Gamma-Ray Burst✓High-end laboratory for Nuclear theoryA nuclear theory Mass-Radius relation for Neutron Star⇒

Image of GRB Black hole + disk?

Mass-Radius

Overview of binary neutron star merger

NS

G.Ws. imprint only information of mass

G.Ws. imprint information of radius

Rapidly rotating massive NS

BH and torus

Mtotal < Mcrit

Mtotal > Mcrit

✓Mcrit depends on the Equation of State, i.e. Mcrit = 1.2-1.7 Mmax

✓Final massive NS or torus around BH are extremely hot, T O(10) MeV ∼ ⇒Neutrino cooling plays an importance role

Set up of binary neutron star○ Shen or Shen-Hyperon EOS based on RMF theory (Shen+,98, Sumiyoshi+,11) ⇒ Mcrit = 2.8-2.9 Solar mass for Shen, 2.3-2.4 Solar mass for Shen-Hyperon EOS○ Neutrino cooling based on GR leakage scheme (Sekiguchi,10)○ Equal mass model with 1.35 Solar mass, i.e., Mtot=2.7 Solar mass

Observed BNSs (Lattimer & Paraksh 06)Mass-Radius

Observation constraint by PSR J1614-2230

ResultDensity color contour on equatorial (x-y) plane = orbital plane

In units of Kilometer

In units of millisecond

Log10(ρ [g/cc])

Gravitational Waveforms

Shen

Shen-Hyperon

NSs orbit around each other

BH formation

Massive NS oscillates

Gravitational Wave Spectrum

frequency

Ampl

itudeSensitivity curves for GW detectors

ShenShen-Hyperon

GWs could be detected if the merger happens within 30 Mpc.

○ ○ Neutrino cooling timescale ∼ 2-3 second○ Huge luminosity ∼1053 erg/s○ Could be detected if it happened within 10 Mpc for HK

Neutrino Luminosity

Shen

Shen+Hyperon

Anti electron neutrinoElectron neutrino

μ, τ neutrino

BH formation

Summary

○ Binary neutron star merger Numerical Relativity simulations with microphysical process for the first time ○ GWs could be detected if it happened within 30 Mpc○ Neutrino could be detected if it happened within 10 Mpc

⇒ Multi messenger astronomy is coming soon !!

Thanks to SR16000 in YITP

Thank you for your attention