Electromagnetic follow-up of gravitational wave transient signal candidates

Pioneering efforts aiming at the development of multi-messenger gravitational wave (GW) and electromagnetic (EM) astronomy have been made. An EM observation follow-up program of candidate GW events has been performed (Dec 17 2009 to Jan 8 2010 and Sep 4 to Oct 20 2010) during the recent runs of the LIGO and Virgo GW detectors. It involved ground-based and space EM facilities observing the sky at optical, X-ray and radio wavelengths. The joint GW/EM observation study requires the development of specific image analysis procedures able to discriminate the possible EM counterpart of GW triggers from contaminant/background events. The paper presents an overview of the EM follow-up program and the image analysis procedures.