Sco-X1search : S2 results C Messenger on behalf of LSC-PULG LIGO Scientific Collaboration Meeting UMich, 4th – 5th June 2005 LIGO-G050290-00-Z

Outline Astrophysical scenario Data Analysis Pipeline S2 results Data-set selection Parameter space F-statistic Search Coincidence test Injections Upperlimits Work in progress and future plans UMich LSC Meeting, 4th – 5th June 2005

Astrophysical Scenario Conjecture for LMXBs: GWs are the limiting physics that prevents NSs from being spun-up to the braking frequency Two models: Density fluctuations – “mountain” on neutron star (Bildsten, 1998; Ushomirsky, Cutler, Bildsten, 2000; Cutler, 2002) fgw = 2 frot R-modes (Andersson et al, 1999; Wagoner, 2002) fgw = 4/3 frot (from Cutler and Thorne 2000) Sco-X1 is a LMXB in an ~18 hr and approximately circular orbit. Expected GW amplitude is ~10-26 UMich LSC Meeting, 4th – 5th June 2005

Data analysis pipeline Data-set selection Template bank generation F-statistic Search Coincidence test Chi-squared test Injections & Upperlimits This is a wide parameter space search !!! UMich LSC Meeting, 4th – 5th June 2005

S2 results : Data-set selection H1 LLO LHO Tstart 731258740 732459161 Tend 731277275 732479463 # SFT 198 332 Tspan 18535 20302 Tobs 11880 19920 frequency Sh1/2 Data-set selected based on sensitivity factor Factor in the noise floor across the search band & sky position sensitivity Limited to 6 hour maximum observation span (Tcomp a Tspan5) UMich LSC Meeting, 4th – 5th June 2005

S2 results : Parameter Space 2+1 dimensional parameter space 2 orbital parameters (Projected Semi-Major axis & Periapse passage) + Intrinsic GW emission frequency Orbital period NOT a search parameter for coherent observation times < 1 week Spin down NOT a search parameter for coherent observation times < 1 month Time of periapsis Projected Semi-Major Axis Projected Semi-Major Axis {1.44 +/- 0.18 sec} at 1 sigma Time of periapsis {731163327 +/- 299 GPS sec} at 1 sigma (phase in the orbit) Frequency range split into 2 bands {474 +/- 10 & 614 +/- 10 Hz} (from QPO observations) METRIC used to place filters in orbital parameter space (frequency projected out) & frequency space (independent of orbital parameters) UMich LSC Meeting, 4th – 5th June 2005

S2 results : F-statistic search L1 619-620 Hz L1 466-477 Hz H1 619-620 Hz H1 466-467 Hz The F-statistic part of the analysis is identical to the isolated pulsar search + binary demodulation. The F-Statistic in the presence of Gaussian noise should be c24 distributed We have “good” and “bad” bands. The “bad” bands deviate significantly from the expected distribution in the tails resulting in statistically unlikely large values. Usually due to large “spikes” not removed by the running median. UMich LSC Meeting, 4th – 5th June 2005

S2 results : Coincidence test The method involves finding orbital templates that could be common closest filters to a possible signal. Have to search a finite range of frequencies around possible event frequency. Factor of 1.4 +/- 20 bins 2F Number of frequency bins Observation span frequency UMich LSC Meeting, 4th – 5th June 2005

S2 results : Candidate Events Proj Semi-Major Axis Proj Semi-Major Axis Time of periapse passage The parameter space contains features after coincidence appearing as planes of events at constant frequency. Event densities in orbital parameter space show no structure Time of periapse passage frequency UMich LSC Meeting, 4th – 5th June 2005

S2 results : Injections & ULs Frequentist upper limits are obtained via signal injections into the dataset h0 Confidence h0 frequency Upperlimits are ~4x1022 in both bands. Coincidence analysis helps us in the case where one detector is “clean” and one detector is “not clean”. UL’s around the 60 Hz power line harmonic at 480 Hz are dominated by very large loudest events inconsistent with Gaussian statistics. UMich LSC Meeting, 4th – 5th June 2005

Work in Progress & future plans S2 paper in initial draft form (FINISH SOON). This coherent pipeline is clearly not the way to search for GW’s from Sco-X1 (but we knew that). An incoherent approach (Virginia Re, Greg Mendell) is the way forward and is currently being tested. The coherent pipeline is currently suitable to place limits on accreting msec X-ray binary pulsars: the parameter space is much smaller allowing far longer observation times (Dominic Kasprzyk). UMich LSC Meeting, 4th – 5th June 2005