Merger of binary neutron stars in general relativity. M. Shibata (U. Tokyo). Jan 19, 2007 at U. Tokyo. I Introduction: Binary neutron stars. Formed after 2 supernovae 4 BNS confirmed: Orbital Period < 0.5days, Orbital radius ~ Million km
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Merger of binary neutron stars in general relativity
M. Shibata(U. Tokyo)
Jan 19, 2007 at U. Tokyo
I. H. Stairs, Science, 304, 547, 2004
Gravitational waves
TGW >> Period
Merge within Hubble time ~ 13.7 B yrs
Merger could happen frequently.
V. Kalogera et al. 04
r
f = 10 Hz
(r = 700 km)
f = 1—1.2 kHz
at onset of merger
(r ~ 25 km)
f ~ 3 kHz ?
during merger
f ~ 7 kHz ?
black hole QNM
~ 8000 revolution
from r=700 km
Massive
NS
Black hole
1st LIGO
LIGO
Advanced LIGO
Frequency (Hz)
TAMA
VIRGO
h(1/Hz^1/2/m)
h～10^-21
f (Hz)
1st LIGO
Current
level
~100 events
per yrs
for A-LIGO
Advanced LIGO
Frequency (Hz)
?
Need
numerical
relativity
Inspiral signal
= well-known
Information on
Neutron star &
Strong gravity
Information on
mass and spin
Central engine
= BH + hot torus
One of the
Central issues
in astrophysics
?
NS-NS merger is
Deserves detailed study
Best approach
GR Simulation is feasible now.
Introduce our latest work.
Mass
Quark star
Lattimer & Prakash
Science 304, 2004
Radius
PSR
J0751-1807
APR
Sly
FPS
2s level
Choose stiff EOSs
Clarify dependence
of GW on EOS
Mass
(a) 1.50 – 1.50 M_sun
(b) 1.35 – 1.65 M_sun
(c) 1.30 – 1.30 M_sun
with APR EOS
Grid #: 633 * 633 * 317 @ NAOJ
Memory： 240 GBytes
1.65 1.35
Apparent
horizon
X-Y
X-Z
Y
Z
~ no disk mass
X
X
Apparent
horizon
X-Y
X-Z
Y
Z
Small disk
mass
X
X
h ~ 5*10^{-23}
at r = 100 Mpc
f = 6.5 kHz
for a=0.75 &
M=2.9M_sun
1st LIGO
100kpc
Too
small
Advanced LIGO
Frequency (Hz)
Lapse
Case 1.3 – 1.3 M_sun ： Massive elliptical NS formation
X-Y
X-Z
Y
Z
X
X
Dotted curve=2e14 g/cc
center＝1.3e15 g/cc
+ mode
Quasi-Periodic oscillation
x mode
Inspiral wave form
For r ＜50Mpc
Detectable !
1st LIGO
Detection
= HMNS
exists
⇒
Constrain
EOS
Advanced LIGO
Frequency (Hz)
Note: Mcrit depends on EOS.
Mcrit ~ 2.8M_sun in APR EOS (M_max~2.20)
~ 2.7M_sun in SLY EOS ( ~2.04)
~ 2.4M_sun in FPS EOS ( ~1.80)
in soft EOSs, threshold mass is small.
Merger
Elliptical HMNS
with diff. rot.
Black hole
GW
emission
~ Equal
mass
Unequal
No disk
Small Disk
Spheroid
T ~ 50 ms
B-fields
effects
BH with
Small disk
Weak short
GRB?
BH with
Heavy disk
Short GRB?
Constrain by GW emission and Shapiro’s time delay
Near edge-on