GEO Sensitivity and First Results

The sensitivity of GEO 600 depends on the bandwidth which in its turn depends on the signal recycling factor. The signal recycling of GEO 600 thus provides the opportunity to change the spectral characteristics of the detector response especially those due to the shot noise limitations. By choosing low or high mirror reflectivites of the signal recycling mirror we can selcect a wideband or a narrowband behaviour, respectively. The center frequency of the maximum sensitivity can be tuned to the desired frequency by shifting the signal recycling mirror thus changing the resonance frequency of the signal recycling cavity.

The LIGO Scientific Collaboration (LSC) was founded in 1997 as a forum for organizing research, publication and all other scientific activities in graviational wave research. At present the LSC comprises about 450 scientists from LIGO, GEO 600 and TAMA 300.

In the Fall of 2002 a first common data run (S1) between all three LIGO detectors and GEO 600 was undertaken consisting of 17 days of mostly uninterrupted operation. Since the detectors had not yet achieved the designed sensitivity, the aim was rather to rehearse data acquisition and data analysis.

The results of the analysis of the first data run S1 have been published in 2004 in the Physical Review D. No gravitational waves have been detected, but in all cases new upper limits have been stablished. The papers are also available at the arXiv Preprint Server:

• Detector Description and Performance for the First Coincidence Observations between LIGO and GEO
  B. Abbott et al. (LSC), Nucl. Instrum. Meth. Phys. Res. A 517 (2004) 154-179
  gr-qc/0308043

• Analysis of LIGO data for gravitational waves from binary neutron stars
  B. Abbott et al. (LSC), Phys. Rev. D 69 (2004) 122001
  gr-qc/0308069

• Setting Upper Limits on the Strength of Periodic GW from PSR J1939 + 2134 Using the First Science Data from the GEO600 and LIGO Detectors
  B. Abbott et al. (LSC), Phys. Rev. D 69 (2004) 082004
  gr-qc/0311023

• First upper limits from LIGO on gravitational wave bursts
  B. Abbott et al. (LSC), Phys. Rev. D 69 (2004) 102001
  gr-qc/0312056

• Analysis of LIGO Data for Stochastic Gravitational Waves
  B. Abbott et al. (LSC), Phys. Rev. D 69 (2004) 122004
  gr-qc/0312088

• Limits on Gravitational-Wave Emission from Selected Pulsars Using LIGO Data
  B. Abbott et al. (LSC), Phys. Rev. Lett. 94 (2005) 181103

• Search for gravitational waves associated with the gamma ray burst GRB030329 using the LIGO detectors
  B. Abbott et al. (LSC), Phys. Rev. D 72 (2005) 042002

• Upper limits on gravitational wave bursts in LIGO's second science run
  B. Abbott et al. (LSC), Phys. Rev. D 72 (2005) 062001

• Search for gravitational waves from galactic and extra-galactic binary neutron stars
  B. Abbott et al. (LSC), Phys. Rev. D 72 (2005) 082001

• Search for gravitational waves from primordial black hole binary coalescences in the galactic halo
  B. Abbott et al. (LSC), Phys. Rev. D 72 (2005) 082002

  First all-sky upper limits from LIGO on the strength of periodic gravitational waves using the Hough transform
  B. Abbott et al. (LSC), Phys. Rev. D 72 (2005) 102004

  Upper limits from LIGO and TAMA detectors on the rate of gravitational-wave bursts
  B. Abbott et al. (LSC), Phys. Rev. D 72 (2005) 122004

  Limits on gravitational-wave emission from selected pulsars using LIGO data
  B. Abbott et al. (LSC), Phys. Rev. Lett. 94 (2005) 181103

The third LIGO Scientific Collaboration (LSC) science run, S3, was performed between November 1st 2003 and January 9th 2004. The commissioning work produced a stably-locking DRMI only about two weeks before the start of S3, and thus left little time for testing and sensitivity optimization. Therefore it was decided that GEO600 would run for about one week, near the beginning of S3, then go offline to allow time to improve the sensitivity and stability of the detector, and finally rejoin the run.

Thus, the GEO600 S3 science run was divided into two separate periods of time, having somewhat different interferometer configurations and sensitivities. The first ran from November 5th through 11th, and the second, from December 30th to January 13th (a few days after the end of the LSC S3). We refer to these as S3 I and S3 II respectively.

The first publication on the S3 run:

• Upper limits on a stochastic background of gravitational waves
  B. Abbott et al. (LSC), Phys. Rev. Lett. 95 (2005) 221101

The S4 run was performed during March 2005.

On November 4, 2005 LIGO started the S5 science run with the aim to take data for more than a year. On May 2, 2006 GEO600 joined S5.