Dr. Ilya Mandel is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at Northwestern University and the Massachusetts Institute of Technology. The PI will develop improved estimates for compact binary coalescence event rates for the Laser Interferometer Gravitational-Wave Observatory (LIGO); conversely, LIGO rates or upper limits will be used to constrain the space of astrophysical parameters describing binary evolution. Dr. Mandel will improve Markov Chain Monte Carlo techniques in order to estimate binary parameters accurately from gravitational-wave observations and to probe systematically the global structure of the parameter space, including the location of possible degeneracies. The PI will explore the use of LIGO intermediate-mass-ratio inspirals (and, eventually, extreme-mass-ratio inspirals) to probe strong-field relativity, study massive compact bodies, and test general relativity. With this goal in mind, the PI will develop improved intermediate-mass-ratio inspiral waveforms and the methodology for intermediate-mass-ratio inspiral detection and parameter estimation. The PI will set up the framework to study the astrophysics of galactic nuclei through intermediate- and extreme-mass-ratio inspiral observations, particularly those with electromagnetic counterparts, and will develop rapid online data analysis tools for this purpose.
Dr. Mandel will also develop a multimedia, web-based tutorial elucidating gravitational-wave detection, data analysis, and the ensuing astrophysical discovery. In addition to presenting the subject of gravitational-wave astronomy, this tutorial will strive to explain the scientific method to the general public and engage the participants in the excitement of scientific discovery. This tutorial will be advertised to local high-school students and will form the backbone of multimedia presentations for the public to be shown at the Adler Planetarium in Chicago and the Boston Museum of Science.
Gravitational waves that will be measured by ground-based and space-based detectors provide a unique way to explore the universe --- to observe in detail a variety of astrophysical and relativistic phenomena. Gravitational waves are an integral part of Einstein's theory of general relativity, and were one of the earliest predictions after its formulation. There exists a significant body of indirect evidence for these ripples in the fabric of space-time that propagate at the speed of light, most famously in the observations of systems of two neutron stars, which lose orbital energy at a rate that matches the expected value from gravitational-wave emission. Gravitational waves have yet to be observed directly, however, making this a very exciting and challenging time in the development of the field of gravitational-wave astronomy. In the work funded by this grant, we have advanced our preparation for extracting the full possible range of astrophysics from gravitational-wave observations that are expected to happen in the next five years. We consolidated predictions for expected rates of mergers of compact binaries composed of neutron stars and black holes, the most likely sources of gravitational-waves for ground-based detectors. We significantly improved the tools for extracting the physical parameters of the merging binaries, such as the component masses and spins, from their gravitational-wave signature. Together with collaborators, we created a public code, LALInference, to aid in parameter estimation; this code is already finding use in a number of publications. We embarked on an ambitious program of combining information from multiple detections, including selections effects, to constrain astrophysical models of evolving stellar binaries. This research had a number of useful (if unanticipated) extra benefits. For example, we developed a new technique for efficiently comparing the quality of two alternative models for explaining the data; this technique has been utilized in other astrophysical applications, such as exploring the apparent mass gap between the heaviest neutron stars and the lightest black holes. And, of course, we have taken every opportunity to train students (supervising or co-supervising 4 undergraduate and 3 graduate students) and share the results of this research and the general excitement of engaging in break-through science with the general public.
