WoU-MMA: The Electromagnetic Counterparts of Gravitational Wave Sources

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A research group at Harvard University will carry out a program to rapidly search for optically-detected counterparts to gravitational wave (GW) events detected by the LIGO, Virgo and Kagra (LVK) GW experiments. The rapid follow up utilizes the Dark Energy Camera and the MMT and Magellan 6.5-meter telescopes to search for optical/near-infrared counterparts. These large-aperture telescopes enable wide-field and galaxy-targeted sensitive searches from both hemispheres on Earth, critical for the discovery of electromagnetic (EM) counterparts (with typical GW localizations of roughly 100 square degrees on the sky and distances of up to a few hundred magaparsecs). Identified counterparts will be studied with multi-wavelength imaging and spectroscopy using radio to X-ray facilities. Students will gain an unparalleled experience in this emerging new field. They will lead the acquisition, analysis, and publication of data across the EM spectrum, and jointly with GW data, thereby providing a broad training in observational astronomy. The project will also integrate this new GW view of the universe into undergraduate education, and narrow the gap between classroom learning and hands-on research through the active participation of students in observing with Harvard-Smithsonian telescopes and through analysis of public GW data.While the GW data for binary neutron stars (BNS) and neutron star-black hole (NS-BH) mergers provide unprecedented insight — the mass and spin distributions of neutron stars and black holes, the merger rates, and sensitive tests of general relativity — the joint detection of EM counterparts will uniquely extend the scientific impact by providing accurate positions, precise distances, an astrophysical context for the binary systems, a probe of matter ejection and nucleosynthesis, and the potential to measure cosmological parameters via the “standard siren” technique. The key optical counterpart for BNS and NS-BH mergers is emission due to the radioactive decay of r-process nuclei synthesized in the merger ejecta – a “kilonova”, already observed in association with the short gamma-ray burst GRB 130603B and with GW170817. The kilonova optical emission is faint and fades rapidly and so large-aperture telescopes are essential for effective follow-up at larger distances than GW170817 (at only 40 Mpc). Advanced LIGO-Virgo (ALV) has demonstrated the ability to detect BNS and NS- BH mergers, and the detectability of EM counterparts has been proven; the event rate is expected to be at least a few per year as ALV and Kagra reach design sensitivity; and the required EM follow-up programs and computational resources are active. This project advances the goals of the NSF Windows on the Universe Big Idea.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.