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Inspiraling Compact Objects: Detection Expectations

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Precession and Inspiral Waveforms. Compact object binaries can precess if spins are ... Precession can modify inspiral waveforms and. decrease the detection ... – PowerPoint PPT presentation

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Title: Inspiraling Compact Objects: Detection Expectations


1
Inspiraling Compact Objects Detection
Expectations
Vicky Kalogera Physics Astronomy Dept
2
In this talk
  • Gravitational Waves and Double Neutron Stars
  • Meet PSR J0737-3039
  • a new strongly relativistic binary pulsar
  • Inspiral Event Rates for
  • NS-NS, BH-NS, BH-BH
  • Precessing Binaries astrophysical expectations

3
Double Neutron Star Inspiral
What kind of signal ?
Do they exist ? YES!
First known NS -NS radio pulsar PSR B191316
inspiral chirp
orbital decay
GW emission causes orbital shrinkage leading to
higher GW frequency and amplitude
PSR B191316
Weisberg Taylor 03
4
  • detection rate r3
  • strength 1/r

Dmax for each signal sets limits on the
possible detection rate
  • What is the expected
  • detection rate out to
  • Dmax ?
  • Scaling up from
  • the Galactic rate

5
Inspiral Rates for the Milky Way
  • Empirical Estimates
  • Based on radio
  • Theoretical Estimates
  • Based on models

of binary evolution until binary compact
objects form. for NS -NS, BH -NS, and BH -BH
pulsar properties and survey selection
effects. for NS -NS only
6
  • Properties of known coalescing DNS pulsars

Galactic Disk pulsars
B191316
B153412
7
  • Properties of known coalescing DNS pulsars

Galactic Disk pulsars
Burgay et al. 2003
8
  • Properties of known coalescing DNS pulsars

Galactic Disk pulsars
Burgay et al. 2003
9
  • Properties of known coalescing DNS pulsars

Galactic Disk pulsars
Burgay et al. 2003
10
  • Properties of known coalescing DNS pulsars

Galactic Disk pulsars
Burgay et al. 2003
M15 (NGC 7078)
212711C 30.5 5.0x10 -18 8.0
11
  • Properties of known coalescing DNS pulsars

Galactic Disk pulsars
Burgay et al. 2003
M15 (NGC 7078)
212711C 30.5 5.0x10-18 8.0
0.68
12
  • Properties of known coalescing DNS pulsars

Mo
Galactic Disk pulsars
Burgay et al. 2003
M15 (NGC 7078)
212711C 30.5 5.0x10-18 8.0
0.68 2.7 (1.36)
13
  • Properties of known coalescing DNS pulsars

?c (Myr) ?sd (Myr) ?mrg (Myr)
(yr-1)
Galactic Disk pulsars
Burgay et al. 2003
14
Radio Pulsars in NS-NS binaries
NS-NS Merger Rate Estimates
Use of observed sample and models for PSR survey
selection effects estimates of total NS- NS
number combined with lifetime estimates
(Narayan et al. '91 Phinney '91)
15
(VK, Narayan, Spergel, Taylor '01)
NG
Nest
pulsar luminosity function L-2 i.e., dominated
by faint, hard-to-detect pulsars
median
25
small-N sample is gt assumed to be
representative of the Galactic population gt
dominated by bright pulsars, detectable to large
distances total
pulsar number is underestimated
16
Radio Pulsars in NS-NS binaries
NS-NS Merger Rate Estimates
(Kim, VK, Lorimer 2002)
It is possible to assign statistical significance
to NS-NS rate estimates with Monte Carlo
simulations
Bayesian analysis developed to derive the
probability density of NS-NS inspiral
rate Small number bias and selection effects for
faint pulsars are implicitly included in our
method.
17
  • Statistical Method
  • Identify sub-populations of PSRs with pulse and
    orbital properties similar to each of the
    observed DNS
  • Model each sub-population in the Galaxy
  • with Monte-Carlo generations
  • ? Luminosity distribution
  • ? Spatial distribution

power-law f(L) ? L-p, Lmin lt L (Lmin cut-off
luminosity)
2. Pulsar-survey simulation ? consider
selection effects of all pulsar surveys ?
generate observed samples
18
Statistical Method
fill a model galaxy with Ntot pulsars
count the number of pulsars observed (Nobs)
3. Derive rate estimate probability
distribution P(R)
19
Statistical Analysis

For a given total number of

pulsars, Nobs follows a

Poisson distribution.




We calculate the best-fit

value of ltNobsgt as a function
of Ntot and the
probability P(1 Ntot)
We use Bayes theorem to
calculate P(Ntot) and finally
P(R)
P(Nobs) for PSR B191316
20
Results
most probable rate Rpeak
P(Rtot)
21
Current Rate Predictions
Burgay et al. 2003, Nature, 426, 531 VK et al.
2004, ApJ Letters, in press
3 NS-NS a factor of 6-7 rate increase
Initial LIGO Adv. LIGO per
1000 yr per yr ref model peak
75 400 95 15 - 275
80 - 1500
opt model peak 20 1000 95
35 - 700 200 - 3700
22
Results Rpeak vs model parameters




23
Current expectations for LIGO II (LIGO
I) detection rates of inspiral events NS -NS
BH -NS BH -BH Dmax 350
700 1500 (Mpc)
(20) (40)
(100) Rdet 5 - 3700
1.5 -1500 15 -10,000 (1/yr)
(10-3 - 0.7) (3x10-4 -0.3)
(4x10-3 -3)
from population synthesis
  • Use empirical NS-NS rates constrain
  • pop syn models gt BH inspiral rates

24
What do/will learn from PSR J0737-3039 ?
  • Inspiral detection rates as high as 1 per 1.5 yr
    (at 95 C.L.)
  • are possible for initial LIGO !
  • Detection rates in the range 20-1000 per yr are
    most probable
  • for advanced LIGO
  • VK, Kim, Lorimer, et al. 2004, ApJ Letters,
    in press
  • NS 2 progenitor is constrained as less
    massive than 4.7 Msolar
  • NS 2 kick is constrained to be in excess
    of 60 km/s
  • and its most probable value is 150 km/s
  • Willems VK 2003, ApJ Letters, submitted
  • Better confirmation of GR
  • First double pulsar with eclipses !
    Lyne et al. 2004, Science, in press
  • constraints on magnetic field and spin
    orientation
  • pulsar magnetospheres
  • measurement of new relativistic effects ?

25
Parkes MultiBeam survey and acceleration searches
Assuming that acceleration searches can perfectly
correct for any pulse Doppler smearing due to
orbital motion How many coalescing DNS pulsars
would we expect the PMB survey to detect ?
VK, Kim et al. 2003
lt Nobs gt 3.6
N.B. Not every new coalescing DNS pulsar will
significantly increase the DNS rates
PMB Nobs
26
Challenges in the near future...
Technical achieve target noise level Data
analysis optimal methods
for signal retrieval detection of
inspiral signal requires template
waveforms and matched filtering
techniques
27
Precession and Inspiral Waveforms
Compact object binaries can precess if spins are
of significant magnitude and misaligned with
respect to the orbital angular momentum.
Precession can modify inspiral waveforms and
decrease the detection efficiency of standard
non-precession searches.
Precession effects are more important for
binaries of high mass ratios (BH-NS) and with
spin tilt angles of the massive object in excess
of 30. (Apostolatos 95)
28
Q What is the origin of spin tilt angles in
compact object binaries ?
Mass transfer episodes in binaries tend to align
spin and orbital angular momentum vectors.
SN NS kick
29
Q What are the expected spin tilt angles ?
gt model BH-NS progenitors and SN kick effects
VK 2000
10 Mo BH 1.4 Mo NS
BH-NS binaries are expected to have significant
spin tilt angles
30
Grandclement, VK, Vecchio 2002 Grandclement VK
2003 Grandclement, Ihm, VK, Belczynski
2003 Buonanno et al. 2003 Pan et al. 2003
Precessing inspiral binaries
with non-precessing templates detection rate
decreases Rdet decrease depends on spin magnitude
and tilt angle
templates that can mimic the precession effects
can increase the detection rate
For a 10-1.4 Mo BH-NS binary
Maximum BH spin
cos(spin tilt angle)
cos(spin tilt angle)
31
Grandclement, Ihm, VK, Belczynski 2003
Rate drop expected from astrophysical
predictions for spin tilts in BH-NS binaries
rate drop by 20-30
Expected rates BH-NS 1.5 -1500 per yr 3x10-4
-0.3 BH-BH 15 -10,000 per yr 4x10-3 -3
3
BH-NS
BH-NS
BH spin magnitude
32
In the near and distant future ...
Initial LIGO 3 NS-NS ---gt
detection possible BH-BH ---gt possible
detection too Advanced LIGO
expected to detect compact object inspiral as
well as NS or BH birth events,
pulsars, stochastic background
past experience from EM there will be
surprises! Laser Interferometry in space
LISA sources at lower frequencies
supermassive black holes and
background of wide binaries
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