SUBMITTED TO APJ Preprint typeset using LATEX style emulateapj v. 5/2/11 THE FIRST TWO YEARS OF ELECTROMAGNETIC FOLLOW-UP WITH ADVANCED LIGO AND VIRGO

We anticipate the first direct detections of gravitational waves with Advanced LIGO and Virgo later this decade. Though this groundbreaking technical achievement will be its own reward, a still greater prize could be observations of compact binary mergers in both gravitational and electromagnetic channels simultaneously. During Advanced LIGO and Virgo’s first two years of operation, 2015 through 2016, we expect the global gravitational-wave detector array to improve in sensitivity and livetime and expand from two to three detectors. We model the detection rate and the sky localization accuracy for binary neutron star mergers across this transition. We have analyzed a large, astrophysically motivated source population using real-time detection and sky localization codes and higher-latency parameter estimation codes that have been expressly built for operation in the Advanced LIGO/Virgo era. We show that for most binary neutron star events the rapid sky localization, available about a minute after a detection, is as accurate as the full parameter estimation. We demonstrate that Advanced Virgo will play an important role in sky localization, even though it is anticipated to come online with only 1/3 as much sensitivity as the Advanced LIGO detectors. We find that the median 90 % confidence region shrinks from ∼500 deg2 in 2015 to ∼200 deg2 in 2016. From hundreds of simulated events unfold some likely detection scenarios. Subject headings: gravitational waves — stars: neutron — surveys 1