Research

I study fast radio bursts (FRBs) and pulsars using observations with radio telescopes and (sometimes) telescopes at other wavelengths. I like finding new FRBs and pulsars with new telescopes or observing modes and I enjoy developing algorithms to enable this. I am a member of the CHIME/FRB Collaboration and I wrote a PhD thesis at McGill University on the detection and morphology of FRBs with the CHIME telescope. Before that, I wrote an MSc thesis at the University of Amsterdam on discovering millisecond pulsars with the LOFAR telescope.

I am currently a Dunlap Postdoctoral Fellow at the University of Toronto's Dunlap Institute for Astronomy and Astrophysics and I am affiliated with Bryan Gaensler's and Keith Vanderlinde's research groups.

Fast radio bursts with CHIME

FRBs are luminous impulses of radio waves that last only a fraction of a second and that are detectable over extragalactic distances. The first FRB was discovered in 2007, but due to the limited sky coverage of most radio telescopes at the time the FRB detection rate took a few years to pick up steam. Despite the now rapidly growing number of detected bursts, the origin of FRBs remains elusive -- although there must be a process at work that is able to generate radio waves of an unprecedented energy. As traveling radio waves are affected by the gas, dust and magnetic fields in between the source and observer, observations of FRBs are a unique probe for the constitution of the material between the galaxies in the Universe.

CHIME (see photo below) is a telescope, originally designed to measure the expansion history of the Universe, that is ideally suited to find FRBs (up to tens per day!). The telescope operates the octave from 400 to 800 MHz and the project to find FRBs is called CHIME/FRB. Amongs other things, I work on the real-time recognition of bursts from known sources, on the commissioning of the telescope and on the characterization of FRB bursts.

Some research highlights from CHIME/FRB so far are the detection of FRBs down to 400 MHz, the discovery of a population of repeating sources of FRBs, the discovery of a 16-day periodic activity in an FRB source and the detection of an FRB-like burst from a Galactic magnetar. We've also observed an apparent dichotomy in the time-frequency structure of bursts from repeating sources of FRBs and one-off events in CHIME/FRB's first catalog of FRBs.

We are currently working towards being able to pin-point all FRBs we detect with CHIME/FRB to within their host galaxies (i.e., to subarcsecond resolution) by constructing smaller versions of the CHIME telescope ("Outriggers") at various locations in North America to perform very-long-baseline interferometry.

CHIME

Millisecond pulsars at the lowest and highest frequencies

Soon after the launch of the Fermi gamma-ray telescope it was discovered that many millisecond pulsars (MSPs) are energetic enough to be gamma-ray emitters. The combined study of the radio and gamma-ray properties of (millisecond) pulsars gives valuable insight in, e.g., particle acceleration in the magnetospheres of neutron stars. Many gamma-ray MSPs have been discovered by targeted radio follow-up surveys of unidentified Fermi gamma-ray sources.

Searches for MSPs at low radio frequencies (below 350 MHz) typically lack the sensitivity for MSPs due to the dispersive effect of the interstellar medium. As a master student at the University of Amsterdam, I helped set up a LOFAR survey for MSPs that aimed to mitigate those effects by using a different computational approach. This survey resulted in the first discoveries of MSPs at very low radio frequencies (135 MHz): pulsars J1552+5437 (2.43 ms), J0952-0607 (1.41 ms) and J0653+4706 (4.75 ms).

Using very similar techniques, we also search for low-frequency radio bursts from FRBs and magnetars with LOFAR, which has resulted in the lowest-frequency detection of an FRB to date.

Open-source software

I am the primary author of dfdt and a contributor to DM_phase and cdmt, open-source software packages for the study of fast radio bursts and pulsars.

Publications

For a complete list, see ADS or arXiv.

2023

  1. CHIME/FRB discovery of 25 repeating fast radio burst sources, CHIME/FRB Collaboration (ZP corresponding author), submitted arXiv

2022

  1. The Green Bank North Celestial Cap Survey. VII. 12 new pulsar timing solutions, J. K. Swiggum, ZP, E. Parent et al., ApJ in press arXiv
  2. Sub-second periodicity in a fast radio burst, CHIME/FRB Collaboration, Nature 607, 256 arXiv

2021

  1. Fast radio burst morphology in the first CHIME/FRB catalog, ZP, D. C. Good, V. M. Kaspi et al., ApJ 923, 1 arXiv
  2. The first CHIME/FRB fast radio burst catalog, CHIME/FRB Collaboration, ApJS 257, 59 arXiv
  3. First discovery of new pulsars and RRATs with CHIME/FRB, D. C. Good, B. C. Andersen, P. Chawla et al., ApJ 922, 43 arXiv
  4. LOFAR detection of 110-188 MHz emission and frequency-dependent activity from FRB 20180916B, ZP, D. Michilli, C. G. Bassa et al., ApJL 911, L3 arXiv
  5. A nearby repeating fast radio burst in the direction of M81, M. Bhardwaj, B. M. Gaensler, V. M. Kaspi et al., ApJL 910, L18 arXiv

2020

  1. A bright millisecond-duration radio burst from a Galactic magnetar, CHIME/FRB Collaboration et al., 2020, Nature 587, 54--58 arXiv
  2. Periodic activity from a fast radio burst source, CHIME/FRB Collaboration et al., 2020 Nature 582, 351–-355 arXiv
  3. Detection of Repeating FRB 180916.J0158+65 Down to Frequencies of 300 MHz, P. Chawla, B. C. Andersen, M. Bhardwaj, et al., 2020, ApJL 896, L41 arXiv
  4. Nine new repeating fast radio burst sources from CHIME/FRB, E. Fonseca, B.C. Andersen, M. Bhardwaj, et al., 2020, ApJL 891, L6 arXiv
  5. A repeating fast radio burst source localised to a nearby spiral galaxy, B. Marcote, K. Nimmo, J. W. T. Hessels, et al., 2020, Nature 577, 190--194 arXiv

2019

  1. CHIME/FRB detection of eight new repeating fast radio burst sources, CHIME/FRB Collaboration, 2019, ApJL 885, L24 arXiv
  2. CHIME/FRB detection of the original repeating fast radio burst source FRB 121102, A. Josephy, P. Chawla, E. Fonseca, et al., 2019, ApJL 882, L18 arXiv
  3. A second source of repeating fast radio bursts, CHIME/FRB Collaboration, 2019, Nature 566, 235--238 arXiv
  4. Observations of fast radio bursts at frequencies down to 400 megahertz, CHIME/FRB Collaboration, 2019, Nature 566, 230--234 arXiv

2018

  1. PALFA single-pulse pipeline: new pulsars, rotating radio transients and a candidate fast radio burst, C. Patel, D. Agarwal, M. Bhardwaj, et al., 2018, ApJ 869, 181 arXiv
  2. The CHIME Fast Radio Burst project: system overview, CHIME/FRB Collaboration, 2018, ApJ 863, 48 arXiv

2017

  1. LOFAR discovery of the fastest-spinning millisecond pulsar in the Galactic field, C.G. Bassa, ZP, J.W.T. Hessels et al., 2017, ApJL 846, L20 arXiv
  2. A millisecond pulsar discovery in a survey of unidentified Fermi gamma-ray sources with LOFAR, ZP, C.G. Bassa, J.W.T. Hessels et al., 2017, ApJL 846, L19 arXiv
  3. Enabling pulsar and fast transient searches using coherent dedispersion, C.G. Bassa, ZP, J.W.T. Hessels, 2017, Astronomy and Computing 18, 40 arXiv

Other writing

  1. For a "Behind the Paper" view on the first FRB detections by CHIME/FRB, Shriharsh Tendulkar and I wrote a blog post for the Nature Research Astronomy Community (2019).
  2. Slides on how to best prepare scientific posters for students of a graduate course in astronomy at McGill University (2017; I still agree with these tips).
  3. Slides on how to best prepare scientific talks for summer undergraduate research students at McGill University (2017; I still agree with these tips).

Student projects

If you are a University of Toronto student interested in doing research with me, please feel free to email me. You can also work with me over the summer through the Summer Undergraduate Research Program in astronomy and astrophysics at the University of Toronto, also when you're not affiliated with the university already.

Teaching

In Fall 2022 I co-taught AST 3100 Astrophysical Transients with Professor Marten van Kerkwijk for graduate students in astronomy and astrophysics at the University of Toronto.

In the press

Contact