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Research

Our Work

VIPER explores the universe and fundamental physics using its most extreme laboratories: supermassive black holes, relativistic binaries, and the low-frequency gravitational-wave sky. We work across the nanoHertz–milliHertz band, from pulsar-timing arrays to the LISA space mission, to understand how massive black holes grow, interact, and test gravity itself.

Our group blends astrostatistics, scientific software, and large-scale simulation. We develop modern Bayesian and simulation-based inference tools for complex PTA and LISA data; build open, well-engineered analysis pipelines that run on real, messy data; and use forward models and end-to-end simulations to forecast the science reach of current PTAs, the International Pulsar Timing Array, and LISA.

VIPER members played critical leading roles in the NANOGrav 15-year (NG15) analysis that provided the first compelling evidence for a cosmic gravitational-wave background at ultra-low frequencies. We are now helping to shape the path from NG15 to LISA, ensuring that when LISA flies, the community has the methods, software, and physical insight needed to turn its data into discovery.

Publications

black hole

Nanohertz Gravitational Wave Astronomy

The first-ever book on pulsar-timing array (PTA) searches for low-frequency gravitational waves. Focusing on the nanohertz band, the book addresses the expected gravitational wave background from numerous supermassive black hole binaries. It details how these extra-Galactic gravitational waves affect the arrival times of radio pulses from Galactic pulsars and the data analysis methods, including classical and Bayesian statistics, used for detection. Serving as a text for advanced students and a reference for experts, key features include a complete derivation of the pulsar timing response, an overview of source astrophysics, and a primer on gravitational-wave data analysis and Bayesian techniques for PTAs.

Author: VIPER Director Stephen Taylor

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