2 In this talk : Gravitational Waves and Double Neutron Stars Meet PSR J :a new strongly relativistic binary pulsarInspiral Event Rates forNS-NS, BH-NS, BH-BHPrecessing Binaries: astrophysical expectations
3 Double Neutron Star Inspiral Do they exist ? YES!What kind of signal ?First known NS -NS:radio pulsar PSR Binspiral chirporbitaldecayGW emission causes orbitalshrinkage leading to higherGW frequency and amplitudePSR BWeisberg &Taylor 03
4 detection rate ~ r3 strength ~ 1/r Dmax for each signal Sensitivity to coalescing binariesDmax for each signalsets limits on thepossible detection rateWhat is the expecteddetection rate out toDmax ?Scaling up fromthe Galactic rate
5 Inspiral Rates for the Milky Way Theoretical EstimatesBased on modelsEmpirical EstimatesBased on radioof binary evolutionuntil binary compactobjects form.for NS -NS, BH -NS,and BH -BHpulsar propertiesand surveyselection effects.for NS -NS only
6 Properties of known coalescing DNS pulsars Galactic Disk pulsarsBBJBurgay et al. 2003CM15 (NGC 7078)
7 Properties of known coalescing DNS pulsars Ps (ms) (ss-1) L400Ps.Galactic Disk pulsarsB xB xJ xBurgay et al. 2003C xM15 (NGC 7078)
8 Properties of known coalescing DNS pulsars Ps (ms) (ss-1) L B9 (G)Ps.Galactic Disk pulsarsB xB xJ xBurgay et al. 2003C xM15 (NGC 7078)
9 Properties of known coalescing DNS pulsars Ps (ms) (ss-1) L B9 (G) d(kpc)Ps.Galactic Disk pulsarsB xB xJ xBurgay et al. 2003C xM15 (NGC 7078)
10 Properties of known coalescing DNS pulsars Ps (ms) (ss-1) Porb (hr)Ps.Galactic Disk pulsarsB xB xJ xBurgay et al. 2003M15 (NGC 7078)C x
11 Properties of known coalescing DNS pulsars Ps (ms) (ss-1) Porb (hr) ePs.Galactic Disk pulsarsB xB xJ xBurgay et al. 2003M15 (NGC 7078)C x
12 Properties of known coalescing DNS pulsars Ps (ms) (ss-1) Porb (hr) e Mtot ( )Ps.MoGalactic Disk pulsarsB x (1.39)B x (1.35)J x (1.24)Burgay et al. 2003M15 (NGC 7078)C x (1.36)
13 Properties of known coalescing DNS pulsars c (Myr) sd (Myr) mrg (Myr) (yr-1)Galactic Disk pulsarsB º.23B º.75J º.9Burgay et al. 2003C º.46M15 (NGC 7078)
14 X Radio Pulsars in NS-NS binaries NS-NS Merger Rate Estimates 3 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 objectsRobust lower limit for the MW (10-6 per yr)Upward correction factorfor faint PSRs: ~X3
15 pulsar luminosity function: hard-to-detect pulsars (VK, Narayan, Spergel, Taylor '01)NGNestpulsar luminosity function:~ L-2i.e., dominated by faint,hard-to-detect pulsarsmedian25%small-N sample is:> assumed to be representative of the Galactic population> dominated by bright pulsars, detectable to large distancestotal pulsar number is underestimated
16 It is possible to assign statistical significance Radio PulsarsinNS-NS binariesNS-NSMergerRate Estimates(Kim, VK, Lorimer 2002)It is possible to assign statistical significanceto NS-NS rate estimateswith Monte Carlo simulationsBayesian analysis developed to derive theprobability density of NS-NS inspiral rateSmall number bias and selection effects for faint pulsars are implicitly included in our method.
17 Statistical MethodIdentify sub-populations of PSRs with pulse and orbital properties similar to each of the observed DNSModel each sub-population in the Galaxywith Monte-Carlo generations Luminosity distribution Spatial distributionpower-law: f(L) L-p, Lmin < L (Lmin: cut-off luminosity)2. Pulsar-survey simulation consider selection effects of all pulsar surveys generate ``observed’’ samples
18 Statistical Methodfill a model galaxy with Ntot pulsarscount the number ofpulsars observed (Nobs)Earth3. Derive rate estimate probability distribution P(R)
19 Statistical Analysis pulsars, Nobs follows a Poisson distribution. For a given total number ofpulsars, Nobs follows aPoisson distribution.We calculate the best-fitvalue of <Nobs> as a function of Ntot and the probability P(1; Ntot)We use Bayes’ theorem tocalculate P(Ntot) and finallyP(R)P(Nobs) for PSR B
21 Current Rate Predictions Burgay et al. 2003, Nature, 426, 531VK et al. 2004, ApJ Letters, in press3 NS-NS : a factor of 6-7 rate increaseInitial LIGO Adv. LIGOper 1000 yr per yrref model:peak95%opt model:peak95%
23 Current expectations for LIGO II (LIGO I) detection rates of inspiral eventsNS -NS BH -NS BH -BHDmax(Mpc) (20) (40) (100)Rdet ,000(1/yr) ( ) (3x ) (4x )from population synthesisUse empirical NS-NS rates: constrainpop syn models > 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 per yr are most probablefor advanced LIGOVK, Kim, Lorimer, et al. 2004, ApJ Letters, in pressNS #2 progenitor is constrained as less massive than ~4.7 MsolarNS #2 kick is constrained to be in excess of 60 km/sand its most probable value is 150 km/sWillems & VK 2003, ApJ Letters, submittedBetter confirmation of GRFirst double pulsar with eclipses ! Lyne et al. 2004, Science, in pressconstraints on magnetic field and spin orientationpulsar magnetospheresmeasurement of new relativistic effects ?
25 Parkes MultiBeam survey and acceleration searches Assuming that acceleration searchescan perfectly correct for any pulseDoppler smearing due to orbital motion…How many coalescing DNS pulsarswould we expect the PMB survey todetect ?VK, Kim et al. 2003< Nobs > = 3.6N.B. Not every new coalescing DNS pulsarwill significantly increase the DNS rates …PMB Nobs
26 Challenges in the near future... Technical: achieve target noise levelData analysis: optimal methodsfor signal retrievaldetection of inspiral signal requires:template waveforms andmatched filtering techniques
27 Precession and Inspiral Waveforms Compact object binaries can precess if spins areof significant magnitude and misaligned withrespect to the orbital angular momentum.Precession can modify inspiral waveforms anddecrease the detection efficiency ofstandard non-precession searches.Precession effects are more important for binaries ofhigh mass ratios (BH-NS) and with spin tilt anglesof the massive object in excess of ~30°.(Apostolatos 95)
28 Q: What is the origin of spin tilt angles in compact object binaries ? BHMass transfer episodesin binaries tend to alignspin and orbital angularmomentum vectors.SN + NS kickBHNSAsymmetric supernovaexplosions can tilt theorbital plane relative tothe spin of thenon-exploding star.
29 BH-NS binaries are expected to have significant spin tilt angles Q: What are the expected spin tilt angles ?> model BH-NS progenitors and SN kick effectsVK 2000BH-NSGrandclement et al. 200310 Mo BH1.4 Mo NSBH-NS binaries are expected tohave significant spin tilt angles
30 Precessing inspiral binaries Grandclement, VK, Vecchio 2002Grandclement & VK 2003Grandclement, Ihm, VK, Belczynski 2003Buonanno et al. 2003Pan et al. 2003Precessing inspiral binarieswith non-precessing templates:detection rate decreasesRdet decrease depends onspin magnitude and tilt angle:templates that can mimicthe precession effectscan increase the detection rate:For a Mo BH-NS binaryMaximum BH spincos(spin tilt angle)cos(spin tilt angle)
31 Expected rates: BH-NS 1.5 -1500 per yr BH-BH 15 -10,000 per yr Rate drop expectedfrom astrophysical predictionsfor spin tilts in BH-NS binariesGrandclement, Ihm, VK, Belczynski 2003rate dropby 20-30%Expected rates:BH-NSper yr3xBH-BH15 -10,000 per yr4x3BH-NSBH-NSBH spin magnitude
32 In the near and distant future ... Initial LIGO3 NS-NS ---> detection possibleBH-BH ---> possible detection tooAdvanced LIGOexpected to detect compact object inspiral as well asNS or BH birth events, pulsars,stochastic backgroundpast experience from EM: there will be surprises!Laser Interferometry in space: LISAsources at lower frequenciessupermassive black holesand background ofwide binaries
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