APL Colloquium

February 26, 2021

Colloquium Topic: Arecibo's Pulsar Legacy: nHz-frequency Gravitational Waves with NANOGrav

The iconic Arecibo Telescope collapsed in December, a terrible loss to the scientific community and especially to the island of Puerto Rico.  For pulsar astronomy, the loss is especially keen, as Arecibo has been at the forefront of pulsar research since they were discovered in 1967.  Arecibo found the first of the millisecond pulsars (MSPs), which have become reliable and extremely stable workhorses of modern astronomy and physics.  The North American Nanohertz Observatory for Gravitational Waves, or NANOGrav, has been observing growing numbers of these systems for over 15 years, and the data look great.  High precision timing of almost 80 MSPs has provided unprecedented sensitivity to the gravitational wave Universe at nHz-frequencies, likely dominated by signals from the population of super-massive black hole binaries in the centers of distant galaxies.  Our sensitivity is increasing each year -- even with Arecibo's loss -- as we continue to add MSPs to our timing array and develop new techniques to remove known systematics, and a gravitational wave detection might be right around the corner. Meanwhile, our observations provide a wide variety of astrophysics, such as new neutron star mass measurements and constraints of the dense matter equation of state.

Colloquium Speaker: Scott Ransom

Scott Ransom is a tenured astronomer with the National Radio Astronomy Observatory (NRAO) in Charlottesville, VA and a Research Professor in the Astronomy Department at the University of Virginia.  His research centers on finding, timing, and exploiting pulsars of various types, using data from many different instruments and at energies from radio waves to gamma-rays.  His main focus is on exotic pulsar systems, such as millisecond pulsars and binaries, and using them as tools to probe a variety of basic physics.  He also spends time on the state-of-the-art signal-processing instrumentation, high-performance computing and software that pulsar (and Fast Radio Burst) astronomy requires.

Scott was a cadet at West Point where he won a Hertz Foundation Fellowship to pursue a PhD in Astronomy at Harvard University.  That he did, interspersed with six years on active duty in the Army as a Field Artillery officer, completing in 2001.  He was a postdoctoral fellow at McGill University in Montreal until 2004 where he moved to NRAO as a staff astronomer.  In 2010 he won the American Astronomical Society's Helen B. Warner Prize “for a significant contribution to observational or theoretical astronomy during the five years preceding the award.”  He is a Fellow of the American Physical Society, a Fellow of the Canadian Institute for Advanced Research, and has authored or co-authored over 280 refereed publications.

When he isn't working on pulsars, Scott is likely tweaking one of his Linux systems, mountain biking, or preferably, rock climbing.