WoU-MMA: Collaborative Research: Gravitational wave cosmology with tidal Love numbers

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The recent detection of gravitational waves (GWs) with the LIGO detector has heralded a new era of GW astrophysics. A research collaboration between the University of Illinois and the University of Chicago will investigate whether careful measurement of the properties of GW events, when combined with traditional astronomical observations can help astronomers to better determine the Hubble constant, H0, which is related to the age and expansion rate of the universe. This research will be integrated with activities aimed at changing the attitudes of middle-school students and the general public toward physics and science, through a newly-developed planetarium show and accompanying standards-aligned lesson plans for middle school teachers, along with public talks by the lead scientists. The research is aimed at studying whether the use of more sophisticated models for the GWs emitted in the coalescence of neutron stars can be used to better measure the Hubble constant. The GW waveform models used today depend on the tidal Love numbers of each star in the binary, dimensionless parameters that measure the rigidity of a body in response to tides. It is known that these constants are related to each other and to the mass ratio of the binary through certain equation-of-state insensitive relations. The use of the latter allows for the extraction of the individual tidal parameters, which can then be used to extract the source masses of the binary components. The waveform, on the other hand, also depends on the redshifted chirp mass of the binary, which can be extracted as an independent parameter. Therefore, the combination of the measurement of the individual source masses through the tidal parameters and the measurement of the redshifted chirp mass should yield a measurement of the redshift, independently from any electromagnetic counterpart. The research will study how well the redshift can be measured through this technique, and whether the accuracy to which H0 can be estimated may be improved by combining this redshift measurement with information from an electromagnetic counterpart or through the stacking of information from multiple GW events. The principal investigator of the project has developed a planetarium show called Einstein’s Gravity Playlist, which is designed to explain general relativity, black holes, and gravitational waves to young audiences. This show will be deployed in the Midwest, starting at the Staerkel Planetarium in Champaign, Illinois, and later at the Adler Planetarium in Chicago. The show will be paired with "eXtreme Gravity for Middle School," a set of fully formed, standards-aligned lesson plans for middle school teachers aimed at supporting them in learning how to deliver content on topics including gravitational lensing, neutron stars, black holes and gravitational waves to middle school students. 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.