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Paper: The BlackGEM Array: Searching for Gravitational Wave Source Counterparts to Study Ultra-Compact Binaries
Volume: 496, Living Together: Planets, Host Stars and Binaries
Page: 254
Authors: Bloemen, S.; Groot, P.; Nelemans, G.; Klein-Wolt, M.
Abstract: The rates and physics of ultra-compact binaries consisting of neutron stars and black holes are poorly known, mostly due to the lack of a good sample to study such systems. In two years from now, the LIGO and Virgo interferometers are expected to be able to directly detect the gravitational waves (GW) emitted by such binaries when they merge, opening up a completely new window on the sky to study ultra-compact binaries. The combination of a GW detection with electromagnetic observations would be especially powerful to characterize the systems and the merger events. Unfortunately, however, the electromagnetic counterparts will be hard to find. The sky localization of the GW detections will be rather poor, with typical error boxes spanning ∼100 square degrees, and the optical sources are expected to be faint (∼22nd magnitude) and not long lasting (∼1 day). In this contribution we discuss the possibilities of finding the electromagnetic counterparts of these binaries, thereby paying particular attention to the dedicated BlackGEM array of optical telescopes that will be deployed at the ESO site in La Silla (Chile) in 2015 and 2016. In the first phase, the array will consist of four 60-cm telescopes with a field of view of 2.7 square degrees each. Apart from going after GW triggers, the array will also perform a deep southern sky survey in Sloan u, g, r, i, and z filters, down to 23rd magnitude in the g band, and a survey to characterize the transient and variable sky on timescales of hours and days. The latter will be a valuable resource to search for variable stars across the sky, including eclipsing, reflecting, and beaming binary stars.
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