Marisageyer

Astronomy grows our grasp of the world out there

ABOUT ME

I am a lecturer at the beautiful University of Cape Town in South Africa, in Mathematics and Applied Mathematics and part of the High Energy Physics, Cosmology and Astrophysics Theory (HEPCAT) team.

I have a background in Theoretical Physics, and since my Master's and PhD studies I have become evermore involved with Astrophysics and observational Radio Astronomy. Before my recent return to academia, I worked as a Operations Scientist at the South African Radio Astronomy Observatory (SARAO), where I got to be a part of the development of the groundbreaking and science-eager radio telescope called MeerKAT. You can keep up to date with the latest MeerKAT developments on the SARAO official website here.

My current research interests as part of the Meertime collaboration include studying pulsar characteristics and conducting pulsar timing. Pulsars are rapidly spinning neutron stars that emit beamed radio emission. We observe the signals from these blitzing objects as periodic pulses using the MeerKAT telescope. I am also the current chair of the African Pulsar Timing (APT) group, aimed at growing the African participation in pulsar science.

Where Meertime studies the pulsars we already know of in mystifying detail, the TRAPUM project, looks to find new ones. We search for the tell-tale metronomic signatures of pulsars in especially the dense stellar populations of Globular Clusters and in Galaxies in the neighbourhood of the Milky Way.

I am passionate about the promotion and development of science and specifically Astrophysics in South Africa. The MeerKAT and upcoming SKAO project offers wonderful job opportunities for new young lovers of maths and science that want to study the universe's puzzles.

MY RESEARCH INTERESTS

Pulsars and pulsar timing

Pulsars are born in supernova explosions when massive stars end their lives. What remains in the explosive debris is a small, but extremely dense, dead stellar core spinning rapidly around its axis emitting radio beams from its magnetic poles. These flashing beams are picked up as a series of repeating radio pulses by our telescopes. Pulsars are the metronomes of the night skies.

The Meertime pulsar timing project running on MeerKAT has already eagerly observed and timed more than a 1000 of these radio clocks, smashing records for the precision with which they are timed. Ultimately, we aim to time a network of pulsars (a pulsar timing array) to search for gravitational waves disturbing their clockwork.

LATEST MEERKAT pulsar news

Fast Radio Bursts

Pulsars and pulsar timing

Observations of these often once-off, but sometimes repeating, luminous radio bursts show that they have traveled from distant galaxies to meet our telescopes.

The TRAPUM programme on MeerKAT scans the skies regularly for new Fast Radio Bursts (FRBs), and has discovered a handful already! With the overall number of known FRBs currently increasing from month to month, we hope to learn a lot more about what creates these mysterious events.

If you want to hear more about the current status of FRBs, you can listen to this episode on the Cosmic Savannah podcast.

FRB CATALOG

The Interstellar Medium

Pulsar signals travel through the Interstellar Medium (ISM) before they reach our telescopes. Electrons adrift in this medium will impart their signature on pulsar signals by slowing down the radio signal and scattering it along multiple pathways.

By studying the effect of the ISM on pulsar signals we get to learn more about the ISM. We are finding that the nearby ISM has more small dense electron clouds than previously expected.

Bumpy Black Holes

The Interstellar Medium

Could we tell from observations if black holes were not as smooth and simple as the standard Kerr model shows? By observing pulsars as probes in orbit around super massive black holes (SMBH) closely, we hope to one day do so. But first we need to catch a pulsar around a SMBH! Fingers crossed that the SKA will find one, perhaps even in the Milky Way.

RECENT PUBLICATIONS

OM Smirnov, I Heywood, M Geyer et al. Mining the time axis with TRON–I. Millisecond pulsars in Omega Centauri, Terzan 5, and 47 Tucanae detected through MeerKAT interferometric imaging, MNRAS 538 (1), L62-L68.

M Chisabi, S Andrianomena, U Enwelum, EG Gasennelwe, A Idris et al. Timing and noise analysis of five millisecond pulsars observed with MeerKAT, MNRAS 537 (3), 2462-2470

V Van Tonder, L Schwardt, A Faustmann, J Gilmore, S Buchner, M Geyer. Increasing Pulsar SNR by Using Spectral Kurtosis as a Radio Frequency Mitigation Technique, Journal of Astronomical Instrumentation, 8 (1)

MT Miles, RM Shannon, DJ Reardon, M Bailes, DJ Champion, M Geyer et al. The MeerKAT Pulsar Timing Array: The first search for gravitational waves with the MeerKAT radio telescope. MNRAS, stae2571

MT Miles, RM Shannon, DJ Reardon, M Bailes, DJ Champion, M Geyer et al. The MeerKAT Pulsar Timing Array: The 4.5-year data release and the noise and stochastic signals of the millisecond pulsar population. MNRAS stae2572

K Grunthal, RS Nathan, E Thrane, DJ Champion et al. The MeerKAT pulsar timing array: Maps of the gravitational-wave sky with the 4.5 year data release. MNRAS, stae2573

V Prayag, L Levin, M Geyer, BW Stappers et al. The TRAPUM large magellanic cloud pulsar survey with MeerKAT I: survey set-up and first seven pulsar discoveries. MNRAS 533 (3), 2570-2581

F Abbate, A Possenti, A Ridolfi, S Buchner, M Geyer et al. Study of consecutive eclipses of pulsar J0024-7204O. MNRAS 532 (4), 4089-4105

E Carli, L Levin, BW Stappers, ED Barr, et al. The TRAPUM Small Magellanic Cloud pulsar survey with MeerKAT–I. Discovery of seven new pulsars and two Pulsar Wind Nebula associations. MNRAS 531 (2), 2835-2863.

PV Padmanabh, SM Ransom, PCC Freire, A Ridolfi et al. Discovery and timing of ten new millisecond pulsars in the globular cluster Terzan 5. A&A 686, A166

Barr, E.D et al. A pulsar in a binary with a compact object in the mass gap between neutron stars and black holes. Science, 383. Jan 2024.

Geyer, M et al. Mass measurements and 3D orbital geometry of PSR J1933−6211. A&A 674, A169, June 2023

Corongiu, A.,Venkatraman Krishnan, V., Freire, P.C.C., Kramer, M., Possenti, A, Geyer, M et al. PSR J1910−5959A: A rare gravitational laboratory for testing white dwarf models. A&A 671, A72, March 2023.

Posselt, A. et al. The Thousand-Pulsar-Array program on MeerKAT -- IX. The time-averaged properties of the observed pulsar population. MNRAS 520 (3), Feb 2023

Chen, W. et al. MeerKAT discovery of 13 new pulsars in Omega Centauri, MNRAS 520 (3), 3847-3856, Jan 2023

Shamohammadi, M. et al. Searches for Shapiro delay in seven binary pulsars using the MeerKAT telescope, MNRAS 520 (2), 1789-1806, Jan 2023

Clark, CJ et al. The TRAPUM L-band survey for pulsars in Fermi-LAT gamma-ray sources. MNRAS, 519 (4), 5590-5606, Jan 2023

Full list of publications

Teaching material and resources

UCT/Meertime Pulsar Timing workshop

NWU/UCT/Swinburne Pulsar Timing workshop

A smaller hands-on two-day workshop held ahead of the MeerKAT@5 conference at SAAO in Cape Town. This covered similar content to the NWU workshop held in September 2023. More details can be found on the meeting website.

NWU/UCT/Swinburne Pulsar Timing workshop

All the content and recordings of an in-person pulsar timing workshop, held at North West University in September 2023, can be found on this website. Credit to Dr Tiaan Bezuidenhout for this detailed product! Have a look at his comprehensive list of helpful online resources on the site.

MeerKAT online Pulsar Timing Workshop

NWU/UCT/Swinburne Pulsar Timing workshop

MeerKAT online Pulsar Timing Workshop

This two-day MeerKAT workshop, held in September 2021, provides an introduction to pulsar timing through lecturing and online tutorials.

You can view the lectures, tutorial and data on the SARAO E-learning platform.

Cosmic Savannah Podcast

SARAO E-Learning portal and YouTube Channel

MeerKAT online Pulsar Timing Workshop

This podcast by Dr Daniel Cunnama (SAAO) and Dr Jacinta Delhaize (UCT) will keep you up to date with the exciting Astronomy developments under African skies!

In Episode 40 you will hear me speak about Fast Radio Bursts.

SARAO E-Learning portal and YouTube Channel

The SARAO E-learning portal hosts an array of online videos, that can also be viewed on the SARAO Web YouTube Channel.

This includes an introductory course in Radio Interferometry under the African Radio Interferometry Winter School material.

SCIENCE ENGAGEMENT & WRITING

I am passionate about science development and communication, and salute the wonderful work done by Astro Molo Mhlaba and the Office of Astronomy for Development.

As a former journalism student, I also enjoy telling research stories in everyday language. Especially the sagas of our night skies!

Please get in touch if you are seeking volunteers for science and astronomy education, or if you require wordsmith assistance to help unravel scientific concepts.

Contact me