Calibration and sensitivity of the Virgo detector during its second science run

TL;DR

This paper details the calibration procedures, sensitivity estimation, and timing accuracy of the Virgo gravitational wave detector during its second science run, highlighting the methods used to achieve near-design sensitivity.

Contribution

It introduces calibration and sensitivity estimation methods for Virgo's second science run, emphasizing absolute timing and uncertainty analysis.

Findings

Virgo achieved sensitivities close to its design during VSR2

Calibration uncertainties were quantified using independent techniques

Sensitivity estimates were provided in the frequency domain

Abstract

The Virgo detector is a kilometer-length interferometer for gravitational wave detection located near Pisa (Italy). During its second science run (VSR2) in 2009, six months of data were accumulated with a sensitivity close to its design. In this paper, the methods used to determine the parameters for sensitivity estimation and gravitational wave reconstruction are described. The main quantities to be calibrated are the frequency response of the mirror actuation and the sensing of the output power. Focus is also put on their absolute timing. The monitoring of the calibration data as well as the parameter estimation with independent techniques are discussed to provide an estimation of the calibration uncertainties. Finally, the estimation of the Virgo sensitivity in the frequency-domain is described and typical sensitivities measured during VSR2 are shown.