A New Relativistic Binary Pulsar: Gravitational Wave Detection and Neutron Star Formation

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A New Relativistic Binary PulsarGravitational
Wave Detection andNeutron Star Formation
Vicky Kalogera Physics Astronomy
Dept with Chunglee Kim (NU) Duncan Lorimer
(Manchester) Bart Willems (NU) Mia Ihm (NU)
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In this talk

• Gravitational Waves and Double Neutron Stars

• Meet PSR J0737-3039
• the most relativistic binary and
• the first double pulsar

• Inspiral Event Rates
• for NS-NS, BH-NS, BH-BH

• Supernovae and NS-NS Formation

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Global network of GW detectors
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Binary Compact Object Inspiral
What kind of signal ?
Do they exist ? YES!
Prototype NS -NS binary 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
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• 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

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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
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Properties of known coalescing DNS pulsars
Galactic Disk pulsars
B191316
B153412
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Properties of known coalescing DNS pulsars
Galactic Disk pulsars
Burgay et al. 2003
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Properties of known coalescing DNS pulsars
Galactic Disk pulsars
Burgay et al. 2003
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Properties of known coalescing DNS pulsars
Galactic Disk pulsars
Burgay et al. 2003
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Properties of known coalescing DNS pulsars
Galactic Disk pulsars
Burgay et al. 2003
M15 (NGC 7078)
212711C 30.5 5.0x10 -18 8.0
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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
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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)
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Properties of known coalescing DNS pulsars
?c (Myr) ?sd (Myr) ?mrg (Myr)
(yr-1)
Galactic Disk pulsars
Burgay et al. 2003
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PSR J0737-3039 A and B in motion!
animation credit John Rowe
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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)
Dominant sources of rate estimate uncertainties
identified
(VK, Narayan, Spergel, Taylor '01)

• small - number observed sample (2 NS - NS in
  Galactic field)
• PSR population dominated by faint objects

Robust lower limit for the MW (10-6 per yr)
Upward correction factor for faint PSRs
1 - 500
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(VK, Narayan, Spergel, Taylor '01)
NG
pulsar luminosity function L-2 i.e., dominated
by faint, hard-to-detect pulsars
Nest
median
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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
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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.
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• 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
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Statistical Method
fill a model galaxy with Ntot pulsars
count the number of pulsars observed (Nobs)
3. Derive rate estimate probability
distribution P(R)
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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
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Results
most probable rate Rpeak
P(Rtot)
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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 200 1000 95
35 - 700 200 - 3700
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Results Rpeak vs model parameters




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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

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How was PSR J0737-3039 formed ?

• current properties
• constrain NS 2
• formation process
• NS kick
• NS progenitor

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NS-NS Formation Channel
animation credit John Rowe
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Evolve the system backwards in time
Willems VK 2004

• GR evolution back to post-SN 2 properties

orbital period (hr)
eccentricity
X
X
N.B. time since SN 2 can be set equal to gt the
spin-down age from maximum spin-up 100Myr
(Arzoumanian et al. 2001)
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Evolve the system backwards in time

• Constraints on pre-SN 2 properties

Willems VK 2004
post-SN orbit must contain pre-SN position (in
circular orbit) A (1-e) lt Ao lt A (1e)
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Evolve the system backwards in time
Willems VK 2004

• Constraints on pre-SN 2 properties

post-SN orbit must contain pre-SN position (in
circular orbit) A (1-e) lt Ao lt A (1e)
NS 2 progenitor helium star to avoid mass
transfer Ao gt Amin RHEmax / rL
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Evolve the system backwards in time
Willems VK 2004

• Constraints on pre-SN 2 properties

post-SN orbit must contain pre-SN position (in
circular orbit) A (1-e) lt Ao lt A (1e)
NS 2 progenitor helium star to avoid mass
transfer Ao gt Amin RHEmax / rL
to satisfy post-SN masses, a, e Mo lt Mmax
f(Vk)
Mo gt 20 Msolar and Vk gt 1215 km/s unlikely

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Evolve the system backwards in time

• Constraints on pre-SN 2 properties -
• allow for mass transfer from the He star

Willems VK 2004
post-SN orbit must contain pre-SN position (in
circular orbit) A (1-e) lt Ao lt A (1e)
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Evolve the system backwards in time
Willems VK 2003

• Constraints on pre-SN 2 properties -
• allow for mass transfer from the He star

post-SN orbit must contain pre-SN position (in
circular orbit) A (1-e) lt Ao lt A (1e)
to form a NS Mo gt 2.1 Msolar
Habets 1986
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Evolve the system backwards in time

• Constraints on pre-SN 2 properties -
• allow for mass transfer from the He star

Willems VK 2004
post-SN orbit must contain pre-SN position (in
circular orbit) A (1-e) lt Ao lt A (1e)
to form a NS Mo gt 2.1 Msolar to avoid a merger
Mo lt 3.5 MPSR 4.7 Msolar
Habets 1986
Ivanova et al. 2003
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Evolve the system backwards in time

• Constraints on pre-SN 2 properties -
• allow for mass transfer from the He star

Willems VK 2004
post-SN orbit must contain pre-SN position (in
circular orbit) A (1-e) lt Ao lt A (1e)
to form a NS Mo gt 2.1 Msolar to avoid a merger
Mo lt 3.5 MPSR 4.7 Msolar
Habets 1986
Ivanova et al. 2003
to satisfy post-SN masses, a, e Mo lt Mmax
f(Vk)
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What is the probability distribution of the
natal kick imparted to NS 2 ?
Willems VK 2004
Assumption isotropic natal kicks
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What is the probability distribution of the
natal kick imparted to NS 2 ?
Willems VK 2004
insensitive to progenitor mass uncertainties
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What is the probability distribution of the
natal kick imparted to NS 2 ?
Willems VK 2004
insensitive to NS age uncertainties
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What is the probability distribution of the
natal kick imparted to NS 2 ?
Willems VK 2004
additional constraints from center-of-mass velocit
y measurements (Willems, VK, Henninger, in prep.)
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Probability distribution of post-SN orbital
characteristics
(Ihm, VK Belczynski, in prep)
Are tight binaries with low eccentricity
surprising ?
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What have we learned already from PSR J0737-3039
(A and B) ? Burgay et al.
2003 Lyne et al. 2004

• 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)

• PSR-B progenitor is constrained to be less
  massive than 5 Msolar
• PSR-B kick is constrained to be in the
  range 60 - 1560 km/s
• the most probable isotropic magnitude is
  150 km/s (Willems VK 2004)

• PSR-A eclipses magnetosphere physics
• PSR-B is torqued by PSR-A (Kaspi et al. 2004)

• PSR-A and B polarimetry As beam is a very
  wide hollow cone
• As spin and magnetic axes nearly aligned
  
• (Demorest et al. 2004)

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What will we learn in the near future ?

• center-of-mass velocity measurements (Ransom
  et al.)
• --gt tighter constraints on NS formation
• --gt PSR-A precession predictions (spin-tilt
  angle and disappearence)
• (Willems, VK, Henninger)

• complete understanding of double PSR geometry
  
• --gt PSR-A precession predictions (Jenet
  Ransom)

• constraints of NS-NS population
  characteristics
• and binary evolution (Ihm, VK
  Belczynski)

• better confirmation of GR
• new relativistic effects ?
• better understanding of PSR magnetospheres ?

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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 ?
N.B. Not every new coalescing DNS pulsar will
significantly increase the DNS rates