Search for gravitational waves associated with GRB 050915a using the Virgo detector

TL;DR

This study reports on Virgo's first search for gravitational waves coincident with gamma-ray burst 050915a, setting upper limits on gravitational wave amplitudes and establishing a methodology for future joint GW-GRB analyses.

Contribution

It introduces a new analysis methodology for detecting gravitational waves from gamma-ray bursts using Virgo data, during its commissioning phase.

Findings

Set upper limits on gravitational wave strain amplitudes around 10^{-20} Hz^{-1/2}

Demonstrated Virgo's potential to constrain GW emission from long gamma-ray bursts

Established a prototype analysis framework for future joint GW-GRB searches

Abstract

In the framework of the expected association between gamma-ray bursts and gravitational waves, we present results of an analysis aimed to search for a burst of gravitational waves in coincidence with gamma-ray burst 050915a. This was a long duration gamma-ray burst detected by Swift during September 2005, when the Virgo gravitational wave detector was engaged in a commissioning run during which the best sensitivity attained in 2005 was exhibited. This offered the opportunity for Virgo's first search for a gravitational wave signal in coincidence with a gamma-ray burst. The result of our study is a set of strain amplitude upper-limits, based on the loudest event approach, for different but quite general types of burst signal waveforms. The best upper-limit strain amplitudes we obtain are h_{rss}=O(10^{-20})Hz^{-1/2} around 200-1500 Hz. These upper-limits allow us to evaluate the level up to which Virgo, when reaching nominal sensitivity, will be able to constrain the gravitational wave output associated with a long burst. Moreover, the analysis here presented plays the role of a prototype, crucial in defining a methodology for gamma-ray burst triggered searches with Virgo and opening the way for future joint analyses with LIGO.