Spring 2023 Seminar Series: Joris Verbiest

Pulsar Timing — Gravitational-Wave Detections and Much More! 

Pulsars are neutron stars that can be detected due to beams of radio waves that are emitted from their magnetic poles. The misalignment of the magnetic axis and the rotational axis furthermore causes these beams to be swept around in space, causing the radio waves to be detected as regular “pulses” of radiation. The incredible rotational stability of these neutron stars allows a plethora of information to be gleaned from the study of the arrival times of these pulses.  

In this talk I will give an overview of the current state of global efforts to detect the impact of gravitational waves on the pulse arrival times from a set of the most precisely timed pulsars. While some initial, tantalising, signals have been seen, a number of corrupting effects complicate efforts to turn these initial signals into detections with high statistical significance. I will comment on the major challenges in this undertaking and illustrate some possible ways forward, commenting on the likelihood of success within the next several years.  

Finally, since the pulsar data obtained for the purposes of gravitational-wave detection contain many other signals as well, I will give a brief overview of some other interesting scientific studies that are being undertaken with these same data. Specifically, I will briefly highlight recent work on the interstellar medium, close and relativistic binary systems, the solar wind and heliospheric magnetic field and the Earth’s ionosphere.  

About the Presenter

Joris Verbiest, IPTA project manager at FSI

1982: born in Belgium 
2000-2003: BSc in Aerospace Engineering, Delft University of Technology, the Netherlands 
2003-2005: MSc in “Advanced Techniques in Radio Astronomy and Space Science” at Chalmers University of Technology, Gothenburg, Sweden 
2005-2009: PhD in radio astronomy at Swinburne University of Technology (Melbourne) and ATNF/CSIRO (Sydney), Australia 
2009: Postdoctoral Researcher at WVU, USA 
2010-2012: Marie-Curie fellow at Max-Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany 
2012-2013: postdoctoral researcher at MPIfR in Bonn, Germany 
2013-2020: juniorprofessor (comparable to assistant professor) in physics at Bielefeld University, Germany 
2020-2022: professor (comparable to associate professor) in astrophysics at Bielefeld University, Germany 
2022-…: IPTA project manager at FSI

So my educational background is largely technological, although my scientific career (from the PhD onwards) has had little to do with technology and is mostly data analysis and is getting closer to data science every year. The scientific highlights have been PTA work (i.e. Pulsar Timing Array work, which is the effort to detect gravitational waves by meticulously analysing the arrival times of pulses from pulsars). During my PhD on that topic, I was the first to demonstrate (based on real data rather than theoretical predictions) that the PTA concept was indeed viable; during my Marie-Curie stint I led the first global combination of PTA data. As a professor, I shifted my focus somewhat to low-frequency radio astronomy (think <250MHz), specifically in order to study the ionised interstellar medium. This naturally forced me into studying the heliosphere and, to some degree, the ionosphere as well. (That looks like a very different topic, but as it turns out, the heliosphere and the ionised interstellar medium are critical for the success of PTA research.)