1. on behalf of the LIGO Scientific Collaboration
The search for gravitational waves from rotating neutron stars: Results from the LIGO Scientific Collaboration
Alberto Vecchio
on behalf of the LIGO Scientific Collaboration
GR17 – Dublin, 22nd July, 2004
LIGO-G Z

2. Outline Analysis of the data from the LIGO second science run (S2):
Method
Results: Upper-limits on 28 isolated neutron stars known as radio pulsars (including Crab)
Searches in progress
Wider parameter space and classes of sources
Variety of algorithms and search approaches
Future outlook
“Mountain” on neutron star
Wobbling neutron star
Accreting neutron star
R-modes
GR17 – 22nd July, LIGO-G Z A. Vecchio

3. Pointing at known neutron stars
Targeted search of GWs from known isolated radio pulsars
First science run (S1) analysis: upper-limit (95% confidence) on PSR J : h0 < 1.4 x (e < 2.9 x 10-4) Phys Rev D 69, (2004)
Second science run (S2) analysis:
28 pulsars (all the ones above 50 Hz for which search parameters are “exactly” known)
Data from the three LIGO interferometers
GR17 – 22nd July, LIGO-G Z A. Vecchio

4. Compute posterior pdfs
Analysis method
Bayesian time domain demodulation
What we are searching for: GWs from non-precessing triaxial pulsars of known position, frequency and spin-down rate
The unknown parameters in a targeted search are
h0 - amplitude of the gravitational wave signal
 - polarization angle
 - angle between rotation axis and line-of-sight
0 - initial phase of pulsar
Heterodyne, low-pass,
average, calibrate
Raw data
Model
Compute joint likelihood
uniform priors
on h0(>0), cosi,
j0, y
Compute posterior pdfs
posterior  prior  likelihood
Compute upper limits
GR17 – 22nd July, LIGO-G Z A. Vecchio

5. The 28 pulsars targeted for S2
B C
B D
B F
B G
B L
B M
B N
B (Crab)
B A
B A B
B (S1) B J J J J J J J
J C
J B
J C
J D
J E J J J
There are 38 known isolated radio pulsars with fGW > 50 Hz, including PSR J (used in S1) and the Crab pulsar
Timing information for 28 pulsars:
Radio observations collected over S2/S3 for 18 of these
ATNF catalogue used for 10 others
The remaining 10 pulsars have not been included in the analysis because of outdated spin parameters (would require more that one template)
GR17 – 22nd July, LIGO-G Z A. Vecchio

6. Summary of S2 results h95 Preliminary – paper to be submitted soon
Crab pulsar S1 J S2
h95 1
PDF
strain
J1910 – 5959D:
h0 = 1.7 x 10-24
Preliminary – paper to be submitted soon
GR17 – 22nd July, LIGO-G Z A. Vecchio

7. Summary of S2 results ? ? Preliminary – paper to be submitted soon
Ellipticity S2
Crab pulsars
Spin-down upper-limit ? S1 J S2
Spin-down upper-limit ?
Preliminary – paper to be submitted soon
GR17 – 22nd July, LIGO-G Z A. Vecchio

8. In progress: wide parameter space searches
Coherent Incoherent
Use F-statistic (Jaranowski et al, 1998) frequency domain analysis over part of the data set (< ½ day) for search at optimal sensitivity:
All sky, wide band (~ 300 Hz ) search for monochromatic, isolated neutron stars
Targeted search on Sco X-1 (accreting neutron star in a binary system)
Sensitivity:
Exploit efficiency of incoherent methods to probe a wide parameter space (all sky, ~200 Hz band, one spin-down parameter) using the full data set
Hough transform (Krishnan et al, gr-qc/ )
Stack-slide (Brady and T. Creighton, 2000)
PowerFlux
Sensitivity:
GR17 – 22nd July, LIGO-G Z A. Vecchio

9. Conclusions Analyses of the second LIGO science run (S2):
Time-domain analysis of 28 known radio pulsars complete.
Best upper-limit on amplitude: PSR J1910 – 5959D: h0 = 1.7 x 10-24
Best upper-limit on ellipticity: PSR J2124 – 3358: e = 4.5 x 10-6
Upper-limit on Crab pulsar is a factor ~30 from spin-down upper-limit
Approaching completion:
All-sky, broadband coherent frequency-domain search
Sco X-1 coherent frequency-domain search
All-sky incoherent searches
Third science run (improved sensitivity LIGO/GEO run)
Time-domain analysis on more pulsars, including binaries
Approaching spin-down upper-limit for Crab pulsar
Extend scope of wide parameter space searches
GR17 – 22nd July, LIGO-G Z A. Vecchio