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Activities of the LIGO Scientific Activities of the LIGO Scientific Collaboration’s Continuous Wave Collaboration’s Continuous Wave

GroupGroup

Xavier Siemens Xavier Siemens for the LSCfor the LSC

University of Wisconsin -- MilwaukeeUniversity of Wisconsin -- Milwaukee

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The CW GroupThe CW Group http://www.lsc-group.phys.uwm.edu/pulgroup/http://www.lsc-group.phys.uwm.edu/pulgroup/

• For the first science run (S1): set upper limit on a single known pulsar For the first science run (S1): set upper limit on a single known pulsar (J1939+2134) using two independent methods (Frequency domain, optimal for (J1939+2134) using two independent methods (Frequency domain, optimal for large parameter space searches, and Time domain, optimal for targeted large parameter space searches, and Time domain, optimal for targeted searches). searches).

• For the second and third science runs (S2, S3) the group has been involved in a For the second and third science runs (S2, S3) the group has been involved in a variety of activities, which include the coherent methods used for S1 as well as variety of activities, which include the coherent methods used for S1 as well as incoherent methods…incoherent methods…

(NASA/CXC/SAO)

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The SignalThe Signal

• We search for gravitational waves generated by neutron We search for gravitational waves generated by neutron star with deviations from axisymmetry.star with deviations from axisymmetry.

For example, isolated neutron star parameters:For example, isolated neutron star parameters:

• Frequency f of source in Solar System Barycenter (SSB)

• Rate of change of frequency df/dt in SSB

• Sky coordinates (, ) of source

• Strain amplitude h0

• Spin-axis inclination • Phase, Polarization ,

Phase evolution

Amplitude modulation

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The SearchesThe Searches

Coherent searches:Coherent searches:

Incoherent searches:Incoherent searches:

- Time-domain:Time-domain: - Targeted - Targeted - Markov Chain Monte Carlo - Markov Chain Monte Carlo

- Frequency-domain:- Frequency-domain: - Isolated - Isolated - Binary, Sco X-1 - Binary, Sco X-1

- Hough transform Hough transform

- Stack-Slide - Stack-Slide

- Powerflux- Powerflux

Searches over narrow

parameter space

Searches over wide parameter

space

Excess power

searches

Ultimately, would like to

combine these two in a

hierarchical scheme

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Time domain searchesTime domain searches

Targeted search:Targeted search:• Targeting radio pulsars with rotational frequencies > 25 Hz at known locations with phase Targeting radio pulsars with rotational frequencies > 25 Hz at known locations with phase

inferred from radio datainferred from radio data

• Upper limits defined in terms of Bayesian posterior probability distributions for the pulsar Upper limits defined in terms of Bayesian posterior probability distributions for the pulsar parametersparameters

• For S2 looked at 28 known isolated pulsars (For S2 looked at 28 known isolated pulsars (gr-qc/0410007gr-qc/0410007) ; best strain upper limits were at ) ; best strain upper limits were at the level of a few x 10^-24 the level of a few x 10^-24

• For S3 will soon extend search to known neutron stars in binaries and will benefit from For S3 will soon extend search to known neutron stars in binaries and will benefit from much improved sensitivity. much improved sensitivity.

TALK:TALK: Matt PitkinMatt Pitkin

• Computational Bayesian technique Computational Bayesian technique

• MCMC can both estimate parameters and generate summary statistics (pdfs, cross-MCMC can both estimate parameters and generate summary statistics (pdfs, cross-correlations, etc)correlations, etc)

• Initial Applications: searches in restricted parameter space and SN1987a (location Initial Applications: searches in restricted parameter space and SN1987a (location known but other parameters not known) known but other parameters not known)

POSTER: John VeitchPOSTER: John Veitch

Markov Chain Monte Carlo:Markov Chain Monte Carlo:

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Isolated SearchIsolated Search

• The detection statistic is the so-called F-Statistic, which is the log of the likelihood maximized The detection statistic is the so-called F-Statistic, which is the log of the likelihood maximized over the unknown parameters [Jaranowski, Krolak and Schutz, PRD58 063001; Jaranowski over the unknown parameters [Jaranowski, Krolak and Schutz, PRD58 063001; Jaranowski and Krolak, PRD59 063003]and Krolak, PRD59 063003]

• For S2 we are doing a wide band (160 Hz-460 Hz) all-sky search for the 10 most sensitive For S2 we are doing a wide band (160 Hz-460 Hz) all-sky search for the 10 most sensitive hours of data for both the Livingston and the Hanford (4km) interferometers.hours of data for both the Livingston and the Hanford (4km) interferometers.

• We are combining the results of the two searches incoherently using a coincidence scheme and We are combining the results of the two searches incoherently using a coincidence scheme and setting upper limits on 1Hz bands using a frequentist scheme based on the loudest coincident setting upper limits on 1Hz bands using a frequentist scheme based on the loudest coincident event.event.

• For S2 we expect upper limits in the strain to be in the range of several x 10^-23 for quiet For S2 we expect upper limits in the strain to be in the range of several x 10^-23 for quiet bands and around 10^-22 for noisy bandsbands and around 10^-22 for noisy bands

TALK: Yousuke ItohTALK: Yousuke Itoh

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Binary SearchBinary Search

• S2 analysis: upper-limit on Sco X-1 using a S2 analysis: upper-limit on Sco X-1 using a

one-stage coherent search over short integrationone-stage coherent search over short integration

time (Tobs = 6 hr).time (Tobs = 6 hr).

• Also uses the F-statistic and a coincidence scheme, Also uses the F-statistic and a coincidence scheme,

and sets a frequentist upper limit based on the and sets a frequentist upper limit based on the

loudest coincident eventloudest coincident event TALK:TALK: Chris MessengerChris Messenger

• In the future: search Sco X-1 and other known LMXBs (~20 targets) with a hierarchical In the future: search Sco X-1 and other known LMXBs (~20 targets) with a hierarchical scheme:scheme:

– Coherent analysis over short data chunksCoherent analysis over short data chunks

– Add incoherently (stack-slide) chunksAdd incoherently (stack-slide) chunks POSTER: POSTER:

Virginia ReVirginia Re

(Artist’s impression: NASA)

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Stack-SlideStack-Slide

• An incoherent search method that stacks and slides An incoherent search method that stacks and slides normalised power to search for periodic sources. normalised power to search for periodic sources.

• Starting point is a set of Short Fourier Transforms (SFTs). Starting point is a set of Short Fourier Transforms (SFTs). Then we:Then we:

• Stack the (normalised) powerStack the (normalised) power

• Slide to correct for Doppler shifts and spin-downSlide to correct for Doppler shifts and spin-down

• Sum and search for significant peaksSum and search for significant peaks

• Can be used as part of a hierarchical search with coherent & Can be used as part of a hierarchical search with coherent & incoherent stagesincoherent stages

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Hough transformHough transform

• An incoherent search method conceptually similar to stack-slideAn incoherent search method conceptually similar to stack-slide

• Select a threshold for the normalised power and label Select a threshold for the normalised power and label frequency bins with a 1 if the threshold is exceeded or 0 frequency bins with a 1 if the threshold is exceeded or 0 otherwiseotherwise

• Slide to correct for Doppler shifts and spin-downSlide to correct for Doppler shifts and spin-down

• Compute the Compute the number countnumber count for a given frequency bin by for a given frequency bin by summing the 0’s and 1’s summing the 0’s and 1’s

• For S2: All-sky search using entire data set with one spin-down For S2: All-sky search using entire data set with one spin-down parameter for the Livingston and Hanford 4km interferometers. Set an parameter for the Livingston and Hanford 4km interferometers. Set an frequentist upper limit using software injectionsfrequentist upper limit using software injections

• Can be used as part of a hierarchical search with coherent & Can be used as part of a hierarchical search with coherent & incoherent stagesincoherent stages

TALK: Badri TALK: Badri KrishnanKrishnan

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PowerfluxPowerflux

• An incoherent search method, similar to stack-slide and HoughAn incoherent search method, similar to stack-slide and Hough

• The main differences are that for this search the sum of the power for The main differences are that for this search the sum of the power for each frequency bin is each frequency bin is

• weighted with the antenna pattern functions of the interferometer, weighted with the antenna pattern functions of the interferometer, and, and,

• weighted by the noise, which is estimated from neighboring weighted by the noise, which is estimated from neighboring frequency bins. The weighting scheme is chosen to minimize the frequency bins. The weighting scheme is chosen to minimize the variance for the estimator of the gravitational wave amplitudevariance for the estimator of the gravitational wave amplitude

• Can be used as part of a hierarchical search with coherent & Can be used as part of a hierarchical search with coherent & incoherent stagesincoherent stages

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Einstein@homeEinstein@home• Like SETI@home, but for LIGO/GEO data. Like SETI@home, but for LIGO/GEO data.

When computer idle, screensaver does ‘real When computer idle, screensaver does ‘real work’.work’.

• American Physical Society (APS) will American Physical Society (APS) will publicize as part of World Year of Physics publicize as part of World Year of Physics (WYP) 2005 activities, and will help with (WYP) 2005 activities, and will help with web site & graphics.web site & graphics.

• Use infrastructure/help from SETI@home Use infrastructure/help from SETI@home developers for the distributed computing developers for the distributed computing parts.parts.

• Goal: pulsar searches using ~1 million Goal: pulsar searches using ~1 million clients. Support for Windows, Mac OSX, clients. Support for Windows, Mac OSX, Linux clients.Linux clients.

• Why?Why?– From our own clusters we can get ~ From our own clusters we can get ~

thousands of CPUs. From thousands of CPUs. From Einstein@home hope to get order(s) Einstein@home hope to get order(s) of magnitude more at low cost.of magnitude more at low cost.

– Great outreach and science education Great outreach and science education tool. tool.

It runs the coherent isolated F-statistic code.It runs the coherent isolated F-statistic code. Still testing but… Read all about it and sign up Still testing but… Read all about it and sign up

at :at :http://einstein.phys.uwm.eduhttp://einstein.phys.uwm.edu

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Upcoming talks/postersUpcoming talks/posters

Talks:Talks:

10:18 10:18 Badri KrishnanBadri Krishnan: The Hough transform search for gravitational waves from pulsars : The Hough transform search for gravitational waves from pulsars

10:55 10:55 Chris MessengerChris Messenger: Bounding the strength of gravitational radiation from SCO-X1 : Bounding the strength of gravitational radiation from SCO-X1

11:13 11:13 Mathew PitkinMathew Pitkin: Searching for gravitational waves from known milisecond pulsars: Searching for gravitational waves from known milisecond pulsars

11:31 11:31 Yousuke ItohYousuke Itoh: All-sky broad band search for continuous waves using LIGO: All-sky broad band search for continuous waves using LIGO

Posters:Posters:

Reinhard PrixReinhard Prix: Matched filtering properties of all-sky searches for continuous : Matched filtering properties of all-sky searches for continuous gravitational waves gravitational waves

Virginia ReVirginia Re: Stack-slide hierarchical searches for gravitational waves from accreting : Stack-slide hierarchical searches for gravitational waves from accreting neutron stars neutron stars

John VeitchJohn Veitch: A time-domain MCMC search technique for gravitational radiation of : A time-domain MCMC search technique for gravitational radiation of uncertain frequency from a targeted neutron star. uncertain frequency from a targeted neutron star.