1. Xavier Siemens for the LSC University of Wisconsin -- Milwaukee
Activities of the LIGO Scientific Collaboration’s Continuous Wave Group
Xavier Siemens for the LSC University of Wisconsin -- Milwaukee

2. The CW Group
4 working groups in the LIGO Scientific Collaboration; Continuous wave, Inspiral, Burst and Stochastic
Co-Chairs of Continuous Waves group:
Mike Landry (LHO Hanford, LIGO)
Maria Alessandra Papa (AEI, GEO)
For the first science run (S1): set upper limit on a single known pulsar (J ) using two independent methods (Frequency domain, optimal for large parameter space searches, and Time domain, optimal for targeted searches).
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 incoherent methods…

3. The Signal
We search for gravitational waves generated by neutron star with deviations from axisymmetry.
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

4. The Searches Coherent searches: Incoherent searches:
Time-domain, bayesian Targeted Markov Chain Monte Carlo - Frequency-domain, F-Statistic Searches: Isolated Binary, Sco X-1
Searches over narrow parameter space
Searches over wide parameter space
Incoherent searches:
Ultimately, would like to combine these two in a hierarchical scheme
Hough transform - Stack-Slide - Powerflux
Excess power searches

5. Time domain bayesian searches
Targeted search: Rejean Dupuis, Matthew Pitkin, Graham Woan
Targeting radio pulsars with rotational frequencies > 25 Hz at known locations with phase inferred from radio data
Upper limits defined in terms of Bayesian posterior probability distributions for the pulsar parameters
For S2 looked at 28 known isolated pulsars (gr-qc/ ) ; best strain upper limits were at the level of a few x 10^-24
For S3 will soon extend search to known neutron stars in binaries and will benefit from much improved sensitivity.
TALK: Matt Pitkin
Markov Chain Monte Carlo: Nelson Christensen, John Vietch, Graham Woan
Computational Bayesian technique
MCMC can both estimate parameters and generate summary statistics (pdfs, cross-correlations, etc)
Initial Applications: searches in restricted parameter space and SN1987a (location known but other parameters not known)
POSTER: John Vietch

6. F-Statistic Isolated Search
Bruce Allen, Yousuke Itoh, Marialessandra Papa, Reinhard Prix, Xavier Siemens
The F-Statistic is the log of the likelihood maximized over the unknown parameters
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.
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 event.
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 bands
TALK: Yousuke Itoh

7. F-Statistic Binary Search
Chris Messenger, Virginia Re, Alberto Vecchio
S2 analysis: upper-limit on Sco X-1 using a one-stage coherent search over short integration time (Tobs = 6 hr).
Also uses a coincidence scheme and sets a frequentist upper limit based on the loudest coincident event
TALK: Chris Messenger
In the future: search Sco X-1 and other known LMXBs (~20 targets) with a hierarchical scheme:
Coherent analysis over short data chunks
Add incoherently (stack-slide) chunks
POSTER: Virginia Re

8. Stack-Slide Mike Landry, Greg Mendell
An incoherent search method that stacks and slides normalised power to search for periodic sources.
Starting point is a set of Short Fourier Transforms (SFTs). Then we:
Stack the (normalised) power
Slide to correct for Doppler shifts and spin-down
Sum and search for significant peaks
Can be used as part of a hierarchical search with coherent & incoherent stages

9. Hough transform Badri Krishnan, Marialessandra Papa, Alicia Sintes
An incoherent search method similar to stack-slide
Select a threshold for the normalised power and label frequency bins with a 1 if the threshold is exceeded or 0 otherwise
Slide to correct for Doppler shifts and spin-down
Compute the number count for a given frequency bin by summing the 0’s and 1’s
For S2: All-sky search using entire data set with one spin-down parameter for the Livingston and Hanford 4km interferometers. Set an frequentist upper limit using software injections
Can be used as part of a hierarchical search with coherent & incoherent stages
TALK: Badri Krishnan

10. Powerflux David Chin, Vladimir Dergachev, Keith Riles
An incoherent search method, similar to stack-slide and Hough
The main difference is that for this search the sum of the power is weighted with the antenna pattern functions of the interferometer
Can be used as part of a hierarchical search with coherent & incoherent stages

11. Currently in testing mode but… Read all about it and sign up at :
Bruce Allen
Like but for LIGO/GEO data. When computer idle, screensaver does ‘real work’.
American Physical Society (APS) will publicize as part of World Year of Physics (WYP) 2005 activities, and will help with web site & graphics.
Use infrastructure/help from developers for the distributed computing parts (BOINC).
Goal: pulsar searches using ~1 million clients. Support for Windows, Mac OSX, Linux clients.
Why?
From our own clusters we can get ~ thousands of CPUs. From hope to get order(s) of magnitude more at low cost.
Great outreach and science education tool. Let people contribute actively not just learn passively.
Currently in testing mode but… Read all about it and sign up at :

12. Upcoming talks/posters
10:18 Badri Krishnan: The Hough transform search for gravitational waves from pulsars
10:55 Chris Messenger: Bounding the strength of gravitational radiation from SCO-X1
11:13 Mathew Pitkin: Searching for gravitational waves from known milisecond pulsars
11:31 Yousuke Itoh: All-sky broad band search for continuous waves using LIGO
Posters:
Reinhard Prix: Matched filtering properties of all-sky searches for continuous gravitational waves
Virginia Re: Stack-slide hierarchical searches for gravitational waves from accreting neutron stars
John Veitch: A time-domain MCMC search technique for gravitational radiation of uncertain frequency from a targeted neutron star.