HEASA 2026 (29 Sep - 02 Oct)

29 Sept 2026, 17:00 → 3 Oct 2026, 10:00 Africa/Johannesburg

The High Energy Astrophysics in Southern Africa 2026 (HEASA 2026) conference will be proudly hosted by the South African Astronomical Observatory (SAAO), at the SAAO Auditorium, in Cape Town, South Africa, from September 29th to October 2nd, 2026.

After the successful twelfth conference in the annual series, High Energy Astrophysics in Southern Africa 2025 (HEASA 2025) held at Glenburn Lodge & Spa, Johannesburg, South Africa, the thirteenth conference, HEASA 2026, will continue its mission of uniting scientists from the Southern African region, the African continent, and around the world who share an interest in high-energy astrophysical phenomena. 

The topics to be discussed at HEASA 2026 include theoretical aspects, multi-wavelength observations, and multi-messenger studies of astrophysical sources. These sources encompass a wide range, such as active galactic nuclei (AGNs), galaxy systems, gamma-ray bursts (GRBs), X-ray/gamma-ray binaries, supernovae and supernova remnants, neutron stars, pulsars, pulsar wind nebulae, and cataclysmic variables (CVs). Additionally, the conference will explore modern aspects of Astro-Particle physics.

Key dates for flight and accommodation bookings:

• Accommodation Check-in: September 29
• Conference Dates: September 30 – October 2
• Accommodation Check-out: Morning of October 3

 

Tuesday 29 September

17:00 → 19:00 Welcome Reception

Wednesday 30 September

08:30 → 09:00 Opening

Convener: David Buckley

08:30 Welcome, Introduction

Speaker: David Buckley (South African Astronomical Observatory)

08:40 Welcome from SA-GAMMA

Speaker: Markus Boettcher

08:50 Welcome from DSTI

Speaker: Mr Takalani Nemaungani (DSTI)

09:00 → 10:05 AGN 1

Chair: David Buckley

09:00 Impact of relativistic jets on galaxy evolution through simulations and observations

Relativistic jets from supermassive blackholes are an important driver of feedback in galaxies with an active black hole. They impact the nearby environment over different physical scales during their lifetime, with varying effects. The jets can act as an important agent of injecting energy in the host's ISM, as confirmed both in observations of multi-phase gas, as well as in simulations. Such interactions have the potential to impact the kinematics of the gas, as well its star formation. However, to what extent such feedback is efficient in impacting the large scale gas in the galaxy is still a question of debate. We have undertaken a multi-faceted approach to understand the impact of such relativistic jets and related phenomenon through a wide ranging campaign of high resolution simulations. Such simulations include new sub-grid physics such as acceleration and evolution of non-thermal electrons, which provide more accurate predictions of non-thermal emission. The results have been further augmented by spatially resolved observations of multi-phase gas in galaxies with such jets, to corroborate the theoretical findings. I will outline the recent results from such on-going works and future directions of research in this context.

Speaker: Dipanjan Mukherjee (IUCAA)

09:31 Exploring the Connection Between Star Formation, AGN Accretion and Mechanical Feedback in the Faint Radio Sky

We investigate the different modes of energy output from active galactic nuclei (AGN) and their connection to black-hole growth in radio-selected galaxies. To achieve this, we use the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Early Science catalogue from the COSMOS field observed at 1.28 GHz, which was derived from an image with a median rms of 2 $\mu$Jy beam$^{-1}$. This catalogue contains 5223 radio sources with optical and near-infrared detections traced up to redshift $z$ $\approx$ 6. Using the CIGALE spectral energy distribution (SED) fitting code, we determine the stellar masses ($M_{\star}$), star formation rates (SFRs), black-hole mass (M$_{\rm BH}$), and AGN luminosity (L$_{\rm AGN}$) of the sources. Using the evolving star-forming main sequence, we classify the radio sources as star-forming (30 $\pm$ 1$\%$), intermediate (31 $\pm$ 1$\%$), or passive (39 $\pm$ 2$\%$) galaxies, and further divide them into low- and high-accretion modes (LAM and HAM) using their Eddington-scaled accretion rates. We find that LAM AGN reside preferentially in more massive, lower-SFR hosts than HAM AGN, suggesting differences in the availability of cold gas that fuels both star formation and AGN activity. We further investigate the relationship between AGN luminosity and black-hole mass across the six host-galaxy and accretion-mode populations. Using 1.4 GHz radio luminosity as a tracer of mechanical power from AGN jets, we will compare the radiative and mechanical outputs across these populations to explore how AGN energy output varies with accretion state and host-galaxy properties.

Speaker: Ms Thando Kekana (University of Johannesburg)

09:52 UHF OBSERVATIONS OF THE TAIL-LIKE REGION OF THE HYDRA A RADIO GALAXY

Hydra A is a FR-I type radio galaxy located at the centre of the Abell 780 cluster with a redshift of z = 0.054. Previous observations of the radio galaxy have been conducted at low frequencies by the Very Large Array (VLA) telescope and using the L-band frequencies of the MeerKAT array telescope. The Chandra X-ray observatory also carried out a detailed survey of the X-ray emission from the radio galaxy. These observations gave us invaluable information regarding the morphology of the galaxy. They revealed that Hydra A is composed of: a bright central core, pair of relativistic jets, pair of inner radio lobes, pair of diffuse outer radio lobes with the south-facing lobe having a tail-like extension and three pairs of X-ray cavities surrounding the lobes.

A spectral break in the radio spectrum is exhibited by the low frequency observations of Hydra A and this has been ascribed to the process of spectral ageing. The spectral age is the time it takes an electron in the lobe region of a radio galaxy to radiate all of its energy through synchrotron and inverse-Compton emission. Minimal research has been done on the tail-like region of Hydra A. One of the few studies done used MeerKAT’s L-band frequencies and reported the tail-like region as having a spectral index that is dissimilar to the lobe regions. This raised questions about the spectral age, electron injection history and possible emission mechanisms in the tail-like region.

The main aim of our research study was to directly measure the spectral break frequency in the radio spectrum of the tail-like region of Hydra A using MeerKAT's UHF observations. This meant we could directly determine the spectral age of the region and see whether it corroborates the previous L-band study and comment on the history of electron injection in the region. In addition to the tail-like region, the southern outer lobe and northern lobe regions were also investigated with the data reduction process producing four UHF-band observations images of Hydra A at central frequencies of 612 MHz, 748 MHz, 884 MHz and 1020 MHz. The Kardashev-Pacholcyzk (KP) spectral age model was best suited to describe the spectrum and we used it to determine the spectral ages of the three regions. The main conclusion was the supplementary UHF dataset being consistent with previous observations without significantly improving the constraints on the spectral age. The spectral age of the tail region was 140.24 Myrs, making it the oldest region of the galaxy which can be attributed to reduced contact with the relativistic jets which continuously inject new electron populations.

Speaker: Sbongakonke Zondo (University of the Witwatersrand)

SIBONGAKONKE_ZONDO_HEASA_SLIDES_2026.pdf

10:05 → 10:30 Coffee Break & Group Picture

10:30 → 12:00 AGN 2

Chair: Markus Boettcher

10:30 From snapshots to movies, in colour, with the Event Horizon Telescope

The Event Horizon Telescope (EHT) is a global mm-VLBI array (230 GHz) that captured the first images of two supermassive black holes, M87 and Sgr A* in 2017. Since then EHT has been expanding with the addition of several new telescopes, as well as a new observing frequency (345 GHz). During its typically annual campaign of ~1-2 weeks, EHT observes the horizon sources as well as a selection of other AGN, accompanied by significant multi-wavelength coverage from the ground and space. The state of the art now includes polarisation, giving insight into the magnetic field structures just outside the black holes, or in the inner jets. In this talk I will summarise some of our most exciting results in the context of questions relating to high-energy emission and particle acceleration. I will also give a perspective on the future, as EHT now moves into the dynamical regime, taking movies instead of snapshots, and the implications for multi-wavelength/multi-messenger connections, particularly CTAO.

Speaker: Sera Markoff (University of Amsterdam)

11:01 RADIO AND GAMMA–RAY VARIABILITY STUDY OF A SAMPLE OF BLAZARS

This study aimed to assess existing multi-wavelength analysis techniques and identify statistical mea- sures that effectively characterize temporal variability of blazars. The data used in the analysis were retrieved from VizieR consisting of three catalogs (VLBA, Effelsberg, and Fermi–LAT observations). From these, a sample of 15 common blazars was selected and their light curves were generated. Furthermore, statistical measures such as skewness and kurtosis and variability metrics including chi-square tests, variability index, modulation index, fractional index, and de-biased modulation index were calculated to quantify the variability. We performed a correlation analysis of each of the variability metrics using a package linmix. We classified the blazars into three variability categories based on our statistical analysis of their light curves and quantitative variability metrics. These cat- egories are; highly variable, moderately variable, and less variable sources. The sources; J1256-0547, J1229+0203, J1635+3808, and J2202+4216 show high variability, typical of flat-spectrum radio quasars, while the sources; J0738+1742, J1653+3945, J1104+3812, and J1221+2813 showed stable emission with minimal flux variations during the observation period of our analysis. Our study found that the Fermi-LAT γ-ray observations presented the highest variability among all three instruments, with modulation indices reaching 63.85±1.38 and fractional indices achieving 322.62±9.57, more than double the Effelsberg values. This indicates that high-energy emission processes are more variable than extended radio emission detected by single-dish telescopes. Moreover, radio variability indices exhibit stronger and more consistent linear correlations than γ-ray indices, possibly due to advanced radio variability analysis techniques and the higher statistical uncertainties inherent in γ-ray photon data.

Speaker: DANIEL NGHINYEKWA (University of Namibia)

Daniel_HEASA_Presentation.pdf

Daniel_HEASA_Presentation.pptx

11:14 Revisiting the AGN discovered in the Fairall survey

Fifty years ago local astronomer Tony Fairall initiated what was originally intended as a southern sky counterpart of the Markarian survey. Markarian's observations had led to the identification of many new Active Galactic Nuclei. One of Fairall's first discoveries was a bright nearby quasar that has become known as "Fairall 9". While most of the over 1500 sources added to the Fairall lists in the two decades thereafter proved to be unremarkable, the survey found dozens of new AGN or suspected AGN. We have re-observed a number of these with the improved spectroscopic instrumentation now in use at SAAO. These new optical spectra, photometric data and now available data in other wavelength regimes allow us to better determine the nature of the Fairall AGNs. We also assess luminosity and spectral changes that occurred in some of these objects.

Speaker: Hartmut Winkler (University of Johannesburg)

11:27 Exploring the Transitional Parameter Space of Blazars using Gamma-ray and X-ray Population Diagnostics

We investigate the $\gamma$-ray and X-ray population properties of changing-look blazars (CLBs) using sources from the Fourth Fermi-LAT Source Catalog Data Release 4 (4FGL-DR4) together with X-ray information from the Living \textit{Swift} XRT Point Source (LSXPS) catalog. The CLB sample is compared with large populations of confirmed BL Lac objects (BLLs) and flat-spectrum radio quasars (FSRQs) using spectral, variability, and broadband properties. In the $\gamma$-ray parameter space, CLBs mainly occupy intermediate and overlap regions between the BLL and FSRQ populations. However, the centroid locations in different parameter planes, along with the PCA and UMAP projections, show that the CLB population lies closer to the FSRQ region. The X-ray analysis also shows a similar behavior, where the overall distribution of CLBs in the X-ray parameter space is found to be nearer to FSRQs than to BLLs. In addition, the X-ray/$\gamma$-ray coupling relations and random-forest classification probabilities are consistent with this trend. Overall, the results suggest that CLBs form a transitional population between the two main blazar subclasses while retaining characteristics closer to the FSRQ population.

Speaker: Dr Zahoor Malik (Department of Physics, University of the Free State, Bloemfontein, 9301, South Africa)

11:40 Long‑term multi‑wavelength SED and variability modeling of the HSP BL Lac PKS 2155-304

PKS 2155-304 is a nearby high‑synchrotron‑peaked (HSP) BL Lac blazar at redshift z ≈ 0.116, and a benchmark source for studying multiwavelength variability in relativistic jets. In this work, we present a time‑dependent modeling study of its spectral energy distributions (SEDs) across the electromagnetic spectrum, using data from H.E.S.S. (very‑high‑energy gamma rays, 2003-2016), Fermi‑LAT (high‑energy gamma rays), Swift‑XRT and UVOT (X‑ray to UV), SMARTS (optical to near‑infrared), Steward Observatory (all covering the period from August 5, 2008, MJD 54683, to December 31, 2018, MJD 58483). This long‑baseline coverage enables a detailed view of its quiescent states, multiwavelength flares, and orphan‑flare episodes.
We construct time‑resolved SEDs at multiple epochs and apply the time‑dependent leptonic diffusive shock acceleration and radiation transfer model in which the relativistic electron population evolves according to injection, acceleration, and radiative cooling. By varying physical parameters such as magnetic field strength, Doppler factor, electron injection rate, and emission‑zone size, we investigate how different activity states - quiescence, gamma‑ray‑dominant, X‑ray‑dominant, and optical‑UV‑dominant flares - emerge from changes in the underlying jet physics. The modeling allows us to derive characteristic acceleration and cooling time‑scales and to assess the degree to which a single emission zone can account for the observed broadband variability.
Our time‑dependent modeling can reproduce the general spectral shapes and flux evolution of PKS 2155-304 across the various wavelength regimes over MJD 54683-58483. The analysis highlights PKS 2155-304 as an excellent benchmark for constraining jet dynamics through time‑resolved SED modeling, and provides a baseline for interpreting future observations with next‑generation facilities such as the Cherenkov Telescope Array and the MAGIC telescope.

Speaker: Ms Shruti Mukherjee (The University of the Free State)

HEASA2026_shruti_new.pdf

HEASA2026_shruti_new.pptx

12:00 → 13:00 Lunch break

13:00 → 14:35 AGN 3

Chair: Sera Markoff

13:00 EHT-multi-wavelength campaigns on AGNi involving gamma-ray observatories

Since 2019, the Event Horizon Telescope (EHT) Collaboration released the first horizon-scale images of M87 and Sgr A, two primary EHT targets and the only systems resolved at horizon scales so far, while the innermost jet regions of a few (other) AGNi were explored at an unprecedented angular resolution. EHT campaigns are accompanied by extensive MWL observations, from radio up to very-high-energy (VHE) γ-rays. Combining EHT's direct horizon-scale imaging and polarization power with broadband MWL light curves and spectral energy distributions offers a unique opportunity to investigate the origin of the variable high-energy emission, the particle acceleration processes at play in the near-horizon plasma, and the disk-jet connection in general. H.E.S.S. has actively participated in these campaigns, along with other VHE γ-ray observatories.
In this talk, I review the lessons learned from the past campaigns on M87 and archetypal blazar 3C 279. The April 2017 3C 279 campaign combined ~20 μas EHT imaging with an extensive MWL data set, where a core flux increase was seen coincident with a superluminal knot ejection, preceded by record UV–optical flaring. Turbulent multi-zone jet model reproduces much of this behaviour, although alternative mechanisms remain possible. For M87, multi-year EHT observations now exist and span very different γ-ray states of the source. M87 and 3C 279 are known for occasional bright VHE and HE γ-ray flares, respectively, and together provide a valuable foundation for population studies in the growing sample of EHT-MWL targets.

Speaker: Dr Anna Luashvili (North-West University, Centre for Space Research)

Luashvili_HEASA_2026.pdf

Luashvili_HEASA_2026.pptx

13:31 Zooming in on the GeV 𝛾-ray flare of the blazar PKS 1725+123 with a multimessenger lens

Blazars are promising sources of extragalactic high-energy astrophysical neutrinos, detected at energies $\gtrsim 10$ TeV by the IceCube neutrino observatory. Here, we report the broadband timing and spectral study of the flat-spectrum radio quasar PKS 1725+123, which has recently emerged as a compelling multimessenger target following its spatial association with the IceCube event IC-201021A. In early 2025, the Fermi-LAT reported high activity, triggering extensive follow-up observations from radio to VHE $\gamma$-rays. During this period, the source exhibited high flux variability across all wavelengths. The {\it Fermi}-LAT analysis suggests rapid variability on timescales of less than 6 hours, implying a compact emission region with a radius of $\sim10^{16}$ cm. Our one-zone leptohadronic model shows that the high-energy $\gamma$-ray flux is produced by a combination of inverse-Compton scattering of external photons from the hot accretion disk and the broad-line region, while the X-ray emission is dominated by synchrotron self-Compton radiation from relativistic electrons. The secondary radiation from the hadronic cascade is found to be sub-dominant in the $\gamma$-ray regime, and the X-ray data constrain the maximum proton energy to $\sim 20$ PeV in the observer frame. Photopion production occurs predominantly with accretion-disk photons, resulting in an estimated muon-neutrino event rate of $\approx 0.3~\mathrm{yr}^{-1}$ during the flaring state with the flux peaking at $\sim1$ PeV. Future observations of TeV $\gamma$-rays by CTA and LHAASO will further constrain cosmic-ray production in this source.

Speaker: Suvas Chaudhary (University of the Free State, Bloemfontein, South Africa.)

Suvas_heasa.pptx.pdf

13:44 Mult-wavelength emission analysis from inverse-Compton initiated cascades

Blazars are a subclass of active galactic nuclei spatially oriented such that our line of sight is closely aligned with their jets. This configuration results in the emissions by relativistic electrons in the jet being Doppler enhanced to higher observed frequencies and luminosities. By contrast, the jets of their parent population, the radio galaxies, point at large angles relative to our line of sight. As a result, this Doppler boosting is weak, which in principle, should result in a lack of $\gamma$-ray detection from these objects. Theoretically, it is well established that $\gamma$-rays originating in the jet can be absorbed by external radiation fields. From this basis, we have also shown that the absorption of $\gamma$-rays, originating in the jet, by optical/ultraviolet photons from the accretion disk and/or the broad-line region produces electrons and positrons (e$^\pm$) which lead to secondary synchrotron and inverse-Compton (IC) cascade emissions. A finding from an earlier work showed that a uniform, oblique magnetic field is sufficient to isotropize these e$^\pm$ pairs and enable high-energy (HE, $E > 100$\,MeV) and very high-energy (VHE, $E>100$\,GeV) $\gamma$-rays to escape at angles much larger than jet opening angles. However, we found that this magnetic field configuration mildly breaks the azimuthal symmetry of escaping $\gamma$-rays. In a more realistic scenario, the magnetic field threading the AGN jet would be helical in shape. In this work, we incorporate a simplified version of the helical magnetic field -- a toroidal magnetic field -- into an IC-initiated cascade emission model. We present a parameter study from the model by examining the broadband spectral energy distributions of a blazar and a radio galaxy.

Speaker: Mfuphi Ntshatsha

HEASA26_mfuphi.pdf

13:57 Angle-Dependent Synchrotron and SSC Polarization from Ordered Magnetic Fields in Blazar Jets

Blazars exhibit a characteristic double-humped, non-thermal spectral energy distribution and polarized emission from radio through X-ray energies. While spectral modeling constrains the physical conditions within the emitting region, it does not uniquely constrain the underlying magnetic-field geometry. Polarization provides an additional diagnostic that is sensitive to the projected magnetic-field structure and radiative geometry of the jet.

We present an angle-dependent, polarization-sensitive one-zone leptonic blazar model that consistently calculates the linear Stokes parameters of synchrotron and synchrotron self-Compton (SSC) emission. We investigate the polarization signatures produced by ordered poloidal, toroidal, and helical magnetic-field configurations as a function of their orientation relative to the line of sight.

Our calculations reveal a strong dependence of the synchrotron and SSC polarization signatures on magnetic-field and viewing geometry. In particular, configurations that produce similar or weakly varying synchrotron polarization can exhibit substantially different SSC polarization signatures, demonstrating that SSC polarization can retain information about the underlying magnetic-field structure that is not readily apparent from the synchrotron component alone. For helical magnetic fields, the polarization can also vary non-monotonically with viewing angle due to changes in the projected field structure and the resulting cancellation of Stokes contributions across the emission region. These results highlight the diagnostic potential of broadband polarimetry for constraining magnetic-field structures in blazar jets and provide a theoretical framework for interpreting current and future X-ray and high-energy polarization observations.

Speaker: Motseothata Tisang

2026_09_30_HEASA.pdf

14:10 Associated HI absorption in the Grus quartet: Insights from MeerKAT

Majority of galaxies live in the group environment, which serve as an intermediate galaxy environment between the field and the cluster, making the investigation of the processes involved vital for understanding galaxy evolution. We present MeerKAT observations of the Grus quartet as part of the MeerChoirs survey. The Grus quartet consists of four large spiral galaxies, NGC 7552, NGC 7582, NGC 7590 and NGC 7599. The HI data reveals a wealth of interaction between the group members, showing evidence for displaced HI and tidal interactions. Most interestingly, two of these galaxies, NGC 7552 and NGC 7582, exhibit prominent HI absorption against their nuclear regions. NGC 7552 hosts a circumnuclear star-forming ring while NGC 7582 hosts an AGN extensively studied across different wavelengths. We find evidence for both inflowing and outflowing HI in both of these galaxies, revealing the presence of cold gas entrained in the outflows. This adds an extra layer of complexity governing the relative importance of internal factors, such as feedback, and external factors, such as interactions between galaxies, in shaping the morphology in HI in a group environment.

Speaker: Mikhail de Villiers (University of Cape Town / South African Astronomical Observatory)

heasa_Mikhail.pdf

heasa_Mikhail.pptx

14:23 Comparitive study of Orphan flare models

Orphan flares are events where flaring takes place in one frequency
unaccompanied by flaring in other bands. Orphan flares are usually secondary flares. We study a very-high-energy orphan flare taking place in 3C279, an FSRQ-type blazar. A primary flare was observed 11 days earlier by Fermi-LAT. We study three models that could explain orphan flares. The hadronic synchrotron mirror model, interpreted as proton synchrotron radiation, constraining the parameters of the relativistic proton population in the jet. The ring-of-fire model, a relativistic plasma "blob" travels along the spine of a blazar jet and passes through a stationary, synchrotron-emitting ring of electrons. And a unified model also known as the stochastic dissipation model where if an orphan flare occurs is based on the distance of the blob from the super massive black hole. The results from the three models are compared.

Speaker: Laenita Lorraine Oberholzer

Orphan_Flare_Model_Comparisons_Laenita_de_Jonge.pdf

14:35 → 15:00 Coffee Break

15:00 → 16:30 Transients 1

Chair: Soebur Razzaque

15:00 The Spectral & Temporal Extremes of Gamma-Ray Bursts

Gamma-ray bursts are the most extreme cosmic explosions, emitting across the electromagnetic spectrum and detected on timescales from milliseconds to years. Modeling the multi-wavelength, multi-timescale observations of gamma-ray burst afterglows leads to insights into the macrophysics of the relativistic outflows and their environments, and the microphysics of the particles and magnetic fields. In this talk, I will focus on observational progress that has been made recently, in particular in the radio regime, with fast follow-up programs using large interferometers; and new insights into electron acceleration by relativistic shocks from multi-wavelength observations.

Speaker: Alexander van der Horst (The George Washington University)

HEASA2026_GRBs_AJvdH.pdf

15:31 A transient search pipeline for the Transient Array Radio Telescope (TART)

Searching for transient events in data taken with the transient array radio telescope (TART) is a challenging task. Localising an actual transient event and ruling out that it is not some kind of radio interference source, all without knowing in advance where or when to look, has been the main cause of the challenge. The TART is a low-cost all-sky interferometer of 24 antennas operating at a central frequency of 1575.42 MHz. With a resolution of about 3.4 degrees, the images are blurry and dominated by bright navigation satellites, making the search for transient events even more difficult. Motivated by such challenges, we began efforts to build a pipeline that reads in raw TART visibility data, builds a model of the known satellites, subtracts them, images what remains, and then tests candidate transients directly on the visibilities with a matched filter. The detection thresholds are measured from the data itself, by checking thousands of random sky directions, rather than assumed from theory. An encouraging result we obtained recently with the pipeline is its detection in the TART data of the solar radio burst of 11 November 2025, at a significance of over 13. The recovered position matches the Sun’s position on that date. This was corroborated with data from four other TART stations, and the event was independently recorded by the RSTN solar monitoring network. In this talk, we present the general workings of the pipeline, give an account of some of its current limitations that we are working to improve on, and then conclude with future plans.

Speaker: Shain Mukungu (University of Namibia)

HEASA2026_Mukungu.pptx

15:44 A search for and modelling of persistent radio sources associated with Fast Radio Bursts.

Fast Radio Bursts (FRBs) are bright, extra-galactic, millisecond-duration transients whose physical origin is still unknown. Luminous compact persistent radio sources (PRSs) have been found to be co-located with a subset of repeating FRBs in some cases. Studying the PRSs may provide clues about the immediate environments of the FRBs, which in turn may reveal the nature of FRB sources. However, the origin of PRSs is also unknown. This work searches for PRSs candidates towards FRBs precisely localised by ASKAP and MeerTRAP using MeerKAT telescope. Complementing this observational search, I am developing a theoretical model of a magnetar wind nebula (MWN), to simulate the spectrum and frequency-dependent surface brightness profile of the PRS as well as the evolution of the dispersion measure and rotation measure. The proposed model aims to explain the origin of faint PRSs and how they are associated with FRBs. This talk present the recent progress from the MeerKAT search and highlights ongoing and planned research directions for probing FRB environments.

Speaker: Ms Lebogang Mfulwane (Centre for Space Research, North-West University,)

Mfulwane-HEASA_Conference-.pdf

15:57 Constraining Jet Structure in Low-Luminosity Gamma-Ray Bursts: A Comparative Analysis of Top-Hat and Gaussian Jets in GRB 171205A

We present a comprehensive multiwavelength afterglow analysis of the nearby LL GRBs GRB~171205A ($z=0.0368$), associated with SN~2017iuk, to constrain its underlying jet structure. Using the standard synchrotron external forward shock framework and Markov Chain Monte Carlo (MCMC) methods, we perform a comparative study of two distinct jet geometries---the canonical top-hat jet and the smoothly structured Gaussian jet---against extensive radio observations spanning $0.25$--$97.5$~GHz and $4.79$--$937.17$~days post-burst. Both models provide reasonable fits to the broadband afterglow data, but the top-hat jet model is statistically preferred with $\chi^2_\nu = 101.99$ compared to $\chi^2_\nu = 114.50$ for the Gaussian model. Information criteria strongly favour the top-hat geometry, indicating that a structured jet with a sharp outer edge better describes the observed emission. The inferred parameters for the top-hat model yield a jet viewing angle $\theta_{\mathrm{obs}} \sim 33.85^\circ$, while the Gaussian model gives $\theta_{\mathrm{obs}} \sim 38.17^\circ$. Both models consistently indicate a low-density circumburst environment ($n_0 \sim 10^{-2.23}$ to $10^{-0.55}~\mathrm{cm}^{-3}$), characteristic of a wind-like medium expected from a massive Wolf-Rayet progenitor. The high reduced chi-squared values ($\chi^2_\nu \sim 100$--$115$) suggest that the simplified synchrotron model may not fully capture all physical complexities, potentially requiring additional processes such as energy injection, inverse Compton scattering, or more sophisticated emission mechanisms. Our results demonstrate the critical importance of multiwavelength radio observations in constraining jet geometry and provide strong evidence for off-axis viewing in LL GRBs.

Speaker: Godson Abbey (The Copperbelt University Zambia.)

HEASA2026 Presentation_Abbey (2).pdf

HEASA2026 Presentation_Abbey_new.pdf

HEASA2026 Presentation_Abbey_new.pptx

16:10 Revisiting Lorentz-factor constraints in blazars and gamma-ray bursts based on polarization-dependent gamma-gamma absorption

Gamma-ray bursts (GRBs: seconds to minutes long flashes of gamma-rays, probably resulting
from either the collapse of a very massive star or from the merger of a neutron star
with another neutron star or a black hole) and jetted active galactic nuclei (in
particular, blazars) are amongst the brightest sources of high-energy gamma-rays in
the Universe. It is well established that the high-energy emission regions in GRBs
and blazars are moving with highly relativistic speeds very close to the speed of
light, in a direction closely aligned with our line of sight. One of the arguments
supporting this is that high-energy gamma-rays observed from these sources would be
absorbed by lower-energy target photons in photon-photon absorption, resulting in
electron-positron pair production, if the emission region was stationary or moving
slowly. Lower limits of the Lorentz factor (and thus, the speed) of the emission
region have been derived from calculations / estimates of the gamma-gamma absorption
opacity on the observed lower-energy radiation fields that are produced in the same
emission region as the gamma-rays. Polarization effects have so far been ignored in
such estimates. However, the low-energy radiation in these sources is likely highly
polarized synchrotron radiation, while the gamma-rays may also be polarized. In this
case, the gamma-gamma absorption opacity may be over-estimated when neglecting its
polarization dependence. The goal of this project is to quantify the error incurred
when estimating minimum jet Lorentz factors neglecting polarization effects. It will
specifically apply the polarization-dependent gamma-gamma absorption formalism of
Boettcher (2014: ApJ, 795, 35) to Lorentz-factor estimates in blazars and GRBs.

Speaker: Denzel Mkhwanazi (Northwest Univeristy)

Denzel_Mkhwanazi_Polarization_HEASA_Conference(1)(1).pdf

Denzel_Mkhwanazi_Polarization_HEASA_Conference(1)(1).pptx

16:30 → 17:30 Poster Session

Note: There are no oral presentations / flash talks for the posters. They have been put into the programme only to have a record of all posters on Indico.

16:30 Assessing the Impact of Voluntary STEM Teaching in Schools as a Community Development Initiative

There are various factors that contribute to the success of learners in the stream of Science, Technology, Engineering and Mathematics (STEM). Considering that these subjects are deemed difficult to most learners and students, most facilitators are constantly seeking and using various methods of teaching these subjects for better outcomes. However, in some cases, external assistance is necessary to ensure that most students succeed. This work reports on the continuous engagement of the volunteering teaching staff who teach STEM subjects at a specific South African school. This previously disadvantaged and unsourced school was accessed in 2022 to assist learners and educators with Mathematics, Mathematics Literacy and Physical Science content. While the performance of the learners will be presented, these will be accompanied by the results of the semi-structured interviews conducted on learners and educators about the impact of this engagement.

Speaker: Buyisiwe Sondezi (University of Johannesburg, Physics Department, P.O. Box 524, Auckland Park, South Africa, 2006)

16:31 Multi-Frequency Characterization of Blazar Light Curves using Fermi-LAT and ALMA Observations

Blazars constitute the most extreme class of active galactic nuclei (AGN), characterized by relativistic plasma jets oriented directly along the line of sight to Earth. Their multi-wavelength emission displays violent variability across broad electromagnetic bands and diverse time scales, providing crucial probes into relativistic jet dynamics, particle acceleration efficiency, and non-thermal radiation mechanisms. Although Flat Spectrum Radio Quasars (FSRQs) and BL Lacertae objects (BL Lacs) exhibit well-documented spectral differences, the exact quantitative relationship between multi-frequency temporal metrics, light curve morphological structures, and the underlying particle dynamics driving variability remains poorly defined across uniform observational frameworks. This study presents a comprehensive, side-by-side comparative analysis combining high-energy γ-ray data from the Fermi Large Area Telescope (Fermi-LAT) with millimeter-wave radio observations from the Atacama Large Millimeter/submillimeter Array (ALMA). A target sample of six blazars, comprising four FSRQs (3C 273, 3C 279, 3C 454.3, and NRAO 530) and two BL Lacs (OJ 287 and PKS 1749+096), was selected from the 4LAC-DR4, FL16Y, and ALMA source catalogs. Light curves in the 0.1–300 GeV and 85–373 GHz energy ranges spanning approximately 16 years of Fermi-LAT observations across 3-day, 7-day, and 30-day temporal cadences as well as complementary 14-years of high-cadence millimeter-wave datasets from ALMA were analyzed. A suite of statistical variability metrics is computed, and flare properties such as duration, peak amplitude, and rise/decay symmetry are measured. Two-sample Kolmogorov-Smirnov statistical tests are applied to evaluate the significance of metric divergence between FSRQs and BL Lacs across both wavebands and all time-binning scales.
Ultimately, this research establishes a synchronized multi-wavelength observational baseline for blazar light-curve variability, potentially providing constraints on jet physics and emission geometry while serving as valuable input for future long-term blazar monitoring programs with ground-based facilities, including the High Energy Stereoscopic System (H.E.S.S.) and the upcoming Africa Millimetre Telescope (AMT) in Namibia.

Speaker: Prof. Michael Backes (University of Namibia)

HEASA CONFERENCE 2026 - POSTER-3.pdf

16:32 Dark matter searches through radio astronomy - imposing mass limits on ALPs

Axion-like particles (ALPs) are potential dark matter candidates which are proposed as a solution to a problem in the current Standard Model of Particle Physics- the lack of an expected violation of Charge Conjugation & Parity (CP) symmetries. ALPs are strong contenders for dark matter candidates as they interact minimally with both “standard” matter and light, and furthermore are low-energy and non-relativistic particles. ALP-photon couplings are expected to lead to radio photon decays, and these signals can be searched for by taking spectroscopic radio data from neighbouring radio sources (chiefly dwarf galaxies) and searching for expected ALP decay signals. Individual bounds can be imposed onto source data, and these local bounds can thereafter be combined and integrated with global bounds.

Speaker: Tristan Jade Wilkinson (University of the Witwatersrand)

16:33 The study of the extended radio galaxies in MERGHERS field

Extended radio galaxies (ERGs) are powerful tracers of galaxy evolution and the interaction between radio jets and their environments. With the sensitivity and resolution of MeerKAT, it is possible to study these radio sources in greater detail than before. This study aims to identify and characterise ERGs in a 1.28 GHz field of the MeerKAT Extended Relics, Giant Halos, and Extragalactic Radio Sources (MERGHERS) survey, specifically that centered on the galaxy cluster ACT-CL J0438-5419. The raw MeerKAT data were processed using the oxkat pipeline, which included a series of data reduction, flagging, first-generation, second-generation, thirdgeneration calibration, and imaging. Primary beam corrections and astrometric checks were applied. A cleaned catalogue of 49 ERGs was built through a combination of automated source detection and visual inspection. Cross-matching with RACS, SUMSS, and GLEAM-X allowed us to compare the radio sources and measure their integrated spectral indices. The DECaLS and AllWISE surveys were used to identify optical and infrared hosts, and to obtain photometric redshifts where available. In-band spectral index maps were produced from sub-band images at 1.0, 1.2, and 1.4 GHz to investigate spatial spectral variations within the sources. The results show a diverse set of radio morphologies, including 3 FRI, 22 FRII, 6 head-tail (HT), 4 wide-angle tail (WAT), 1 Z-shaped, and 13 unclassified sources. A total of 25 hosts were identified in the optical/infrared, with photometric redshifts for 17 of them. Our findings reveal that the FRII population dominates the field and tends to have higher radio luminosities, while some HT and FRII sources are detected at redshifts above 1.25. The spectral index (α), which describes how a source radio flux density changes with frequency, is a key tracer of the underlying emission processes. The in-band spectral index maps reveal the expected trend of steepening (α À ´0.5) in the outer lobes, consistent with synchrotron ageing of electrons, while flatter spectra (α Á ´0.5) appear near the cores, marking regions of ongoing jet activity. This work demonstrates the ability of MeerKAT to resolve faint and complex ERG structures. By combining visual classification, cross-matching, and spectral mapping, we show that source morphology and spectral properties vary with environment. FRI and WAT radio sources are typically found in denser regions, while most FRII sources are found in the field. These findings provide a foundation for expanding the analysis to the full MERGHERS Tier 1 sample, enabling comparisons across multiple fields to better understand how the environment influences the evolution of extended radio galaxies.

Speaker: Banele Mthembu (University of KwaZulu-Natal (National Astrophysics & Space Science Programme))

16:34 Probing Synchro-Curvature and Pair Synchrotron Emission from the Millisecond-Pulsar Population of 47 Tucanae

Globular clusters are established high-energy sources, with their GeV emission generally attributed to unresolved populations of millisecond pulsars (MSPs). However, the physical origin of different components of their broadband spectra remains uncertain. We investigate the emission from 47 Tucanae using a population-scaled, phase-averaged model that combines synchro-curvature radiation from accelerated primary particles with synchrotron radiation from secondary electron-positron pairs in MSP magnetospheres. The model provides a physically motivated description of the observed spectral energy distribution, with the primary synchro-curvature component shaping the GeV spectrum and the pair synchrotron component contributing at lower energies. X-ray measurements and TeV upper limits provide additional consistency constraints. The present calculation focuses on magnetospheric emission from the unresolved MSP population, while cluster-scale particle transport and diffuse synchrotron and inverse-Compton emission will be incorporated in future work.

Speaker: Hambeleleni Davids

16:35 Probing Cosmic Dawn through galaxy clusters: the SZE-21cm as a differential observable for SKA-Low

Galaxy clusters offer an unconventional route to the global 21 cm signal. The low-frequency background passing through the hot intracluster medium is inverse Compton-scattered, producing a cluster-localised spectral distortion, the SZE-21cm, that carries the imprint of the global signal. Since it is measured as a difference between a cluster sightline and nearby blank sky, the effect does not depend on absolute calibration of the sky monopole and is well suited to interferometric observation. This work makes the case for the SZE-21cm as a Cosmic Dawn probe. Simulated differential observations with realistic instrumental effects show that the spectrum can potentially be recovered with SKA1-Low and used to independently test anomalous global-signal claims such as EDGES. A variance-aware analysis across physically motivated Cosmic Dawn scenarios further shows that heating histories leave separable imprints in the SZE-21cm once intrinsic 21 cm sky fluctuations are accounted for, with robust discrimination requiring stacking over large cluster samples. The SZE-21cm offers an independent consistency test on early-Universe heating histories, complementary to global-signal and power-spectrum approaches, and worth keeping in view as SKA-Low moves towards Science Verification.

Speaker: Charles Takalana (IAU-OAD)

16:36 Extragalactic radio jets at sub-kpc scale

Relativistic plasma jets are conduits through which energy, momentum, and angular momentum are transported from the centre of active galactic nuclei (AGNs) to vast distances, extending from sub-parsec to megaparsec scale structures such as hotspots and lobes where they terminate, influencing the so-called AGN feedback processes. Although sufficient energy input is available from jets, both how feedback is regulated and the processes required to heat the intergalactic medium remains open. To resolve them, we need to map jet outflows and their interaction with the environment. Using high-resolution and high-sensitivity radio data from the e-MERLIN jets legacy programme, we attempt the highest fidelity imaging to-date of the inner jet structure in the radio quasar 3C 273. The goal is to resolve the jet structures where they first brighten and place constraints on the dynamics and kinematics of the radio jet within the vicinity of the AGN. In this paper, I will present preliminary results from our study and discuss future work on spectral and polarimetric analysis on 3C 273 and other sources of similar type.

Speaker: Paul Chitembwa (University of Manchester)

16:37 Chemical ABundances of Type-2 AGN in Different Environments

The chemical abundance of active galaxies, which host active galactic nuclei (AGN) at their centre, remains poorly studied, most often due to the difficulty of removing the effect of AGN in metallicity measurements. In particular, the chemical abundance of active galaxies in different environments, including clusters and groups of galaxies, is still unknown. In this work, we use a novel HCm code (HII-CHI-mistry) adapted to measure the chemical abundance of type-2 AGN. We measure the oxygen abundance (12 + log(O/H)), the nitrogen abundance (log(N/O)), and the ionisation parameter (logU) for ~12000 type-2 AGN selected from the SDSS survey. We analyse the metallicity properties of type-2 AGNs in relation to other properties of AGN host galaxies, such as morphology, stellar mass and star
formation rate (SFR), and in terms of the environment. In addition, for galaxies in groups and clusters, we study the metallicity properties in relation to the properties of the galaxy groups/clusters (e.g., the
cluster-centric distance and the number of galaxies in the group/cluster). We do not observe a clear and strong mass-metallicity relation, although, we do observe that in groups and clusters, the 12 + log(O/H) abundance is higher in galaxies with higher stellar mass. We find that the 12 + log(O/H) abundance decreases with increasing SFR in all environments. We do not find a fundamental plane of type-2 AGN,suggesting more complex scenarios in the behaviour of stellar mass, SFR and metallicity when AGN are present, compared to pure star-forming galaxies. We find that type-2 AGN hosts, both early- and late-type, have on average higher 12 + log(O/H) abundances in groups and clusters compared to field galaxies, independent of redshift. Our results indicate that, although type-2 AGN in groups and clusters have on average higher metallicities for a given stellar mass, neither simple group or cluster membership nor cosmic-centric distance seems to drive this effect. Finally, with this work, we provide the largest catalogue of chemical abundances of type-2 AGN to date.

Speaker: Mehbuba Ahmed Mohammed (Space Science and Geospatial Institute (SSGI), and 10Academy)

16:38 MeerKAT Detection of a Giant Radio Halo in Abell S1063

We present MeerKAT 1.28 GHz radio-continuum results for the Frontier Field cluster Abell S1063 at $z = 0.351$. The observations reveal a giant radio halo extending over $\sim 1.96$ Mpc, with an integrated flux density of $S_{1.28\,\mathrm{GHz}} = 15.43 \pm 2.73~\mathrm{mJy}$. Its large physical extent and comparatively low radio power place it among the relatively underluminous giant radio haloes. Its diffuse radio emission broadly follows the distribution of the cluster’s hot X-ray gas, elongated towards the north-east along the proposed merger axis. Combining the MeerKAT measurement with flux-density measurements available in the literature, we find that the integrated radio spectrum steepens above $\sim 1.5 \ \mathrm{GHz}$. The halo morphology, radio–X-ray alignment and curved spectrum are consistent with an ageing relativistic electron population re-accelerated by merger-driven turbulence. We will give consideration of the results together with the 10 subtracted radio galaxies lensed by the cluster.

Speaker: Portia Legodi (University of South Africa)

16:39 Probing Intrabinary Shock Properties in Spider Pulsars through Frequency-Dependent Radio Eclipses

In spider pulsar binaries, the energetic pulsar wind continuously ablates the low-mass companion star, driving a complex intrabinary shock and producing a dense local plasma-filled environment. This interaction region acts as a unique laboratory for high-energy astrophysics, yet its precise geometry and local properties remain challenging to constrain. In this work, we present a theoretical modelling framework to investigate the physical conditions of the intrabinary shock through simulated frequency-dependent radio eclipses. Our simulations show that treating the intrabinary shock as a finite three-dimensional volume, with a smoothly varying plasma-density distribution, produces more realistic eclipse morphologies than an idealised thin-shell treatment. The three-dimensional geometry further shows how the orbital motion of the system can sweep the ablated plasma into a cometary tail, naturally producing an asymmetric eclipse via a delayed egress. Furthermore, the model demonstrates how the shock stand-off distance and orbital inclination strongly influence the overall extent of the radio eclipse. By demonstrating the model's behaviour and sensitivity to shock geometry, density weighting, and geometry, this framework provides a robust foundation for interpreting complex propagation effects and for further model development in future. Inferences from this model are complementary from conclusions drawn from high-energy data, adding to a holistic picture of spider binaries.

Speaker: Thulo Letsele (Centre for Space Research)

16:40 Hard X-ray Properties of Nearby VHE-Emitting Radio Galaxies: NGC 1275 and Centaurus A

Radio galaxies are important laboratories for studying the physics of active galactic nuclei and their relativistic jets. In this study, I will investigate the multi-epoch hard X-ray emission from two nearby radio galaxies, NGC 1275 and Centaurus A. We present a multi-epoch study of the hard X-ray emission from the nearby radio galaxies Centaurus A and NGC 1275 using NuSTAR observations. The sources are investigated through spectral fitting with absorbed power-law models that include an Fe Kα emission line, allowing us to characterize their spectral shapes, line properties, absorption, and flux variability across different epochs. For Centaurus A, the photon index remains relatively stable at around Γ ≈ 1.82–1.85, while variations are observed in the absorbing column density, Fe Kα line width, and hard X-ray flux. Similarly, the NGC 1275 observations show a generally stable power-law continuum with Γ ≈ 1.7–2.0, accompanied by changes in the continuum normalization and Fe Kα line properties.

Speakers: B. van SOELEN (Department of Physics University of the Free State Bloemfontein 9301 South Africa), Suvas Chaudhary (University of the Free State, Bloemfontein, South Africa.)

suvas_RGs_HEASA.pdf

16:41 Investigating changes in the circumstellar disc of PSR B1259-63/LS2883 using optical SALT spectra

Gamma-ray binaries are a rare class of high-mass binary systems in which the non-thermal energy spectrum peaks in the gamma-ray regime. PSR B1259-63/LS2883 falls under this rare class and is one of the only three sources where the compact object has been identified as a young pulsar. This system has a 3.4 year orbital period and consists of a 48 ms pulsar and an O9.5 Ve star. The non-thermal emission in the system originates from the shock that forms between the pulsar and stellar winds, preventing accretion onto the system. The orbit of the pulsar around the optical companion is highly eccentric (e ∼ 0.87), resulting in the pulsar moving through the inclined decreation disc of the Oe star around periastron. This phenomenon is observed as an eclipse in the pulsed radio emission, as well as two peaks in the unpulsed radio and X-ray light curves, coinciding with the disc crossings. The system shows variability from one periastron to the next that is proposed to be due to changes in the size and/or structure of the circumstellar disc, which results in a change in the shock structure. In this work SALT optical spectra taken between 2018 and 2021, as well as around the 2024 periastron passage, are used to investigate how the circumstellar disc changes over the orbital phase.

Speaker: Mahike Kilian Kilian (University of the Free State)

M_Kilian_Flash_Talk_Poster_Session.pdf

M_Kilian_HEASA_poster_final.pdf

16:42 Probing Blazar-Jet Structure with Multi-Zone Synchrotron Polarization Modelling

The synchrotron radiation from blazars is produced by populations of relativistic electrons within their jets. This radiation is intrinsically polarized. However, the observed polarization depends strongly on the geometry and physical conditions of the emitting region. It may also be affected by emission from other components, such as contributions from the host galaxy. Thus, connecting the observed polarization trends to the underlying magnetic-field structure and plasma conditions remains challenging. In this study, a multi-zone synchrotron model is used to investigate how magnetic-field configuration, viewing angle, and electron distribution affect the observed emission and polarization. The model consists of a discrete grid of cells, each representing a small volume of the emitting plasma. Every cell is assigned a magnetic-field vector and a relativistic electron population. The synchrotron emissivity and self-absorption coefficients are calculated in the co-moving frame of each cell and then transformed to the host-galaxy frame. Polarized radiative-transfer equations are solved to integrate the emission along an arbitrary line of sight and used to calculate the Stokes parameters for the region. The results can be used to model the observed spectral energy distribution, degree of linear polarization, and polarization angle for complex multi-zone emission regions. We present our initial results for a static jet model. In this model, the effects of different magnetic-field configurations, electron distributions, and viewing angles are investigated. These results will provide a strong framework for testing which magnetic-field structures can reproduce the observed polarization behaviour within relativistic blazar jets.

Speaker: Jacques Redelinghuys (University of the Free State)

HEASA_2026_Blazar_Polarization_Poster_Final_3.0.pdf

16:43 The role and impact of laboratory demonstrators, laboratory managers, and lecturers in enhancing students' learning and understanding

Despite the progress in technology that allows many undergraduate experiments in the physical sciences to be simulated, these digital models cannot fully replace the learning benefits of real laboratory work. Hands-on laboratory experiences remain a part of undergraduate science education. They help students build skills, think scientifically, solve problems, and understand the uncertainties that come with real scientific research. In education, the success of lab learning depends on collaboration among lecturers, laboratory managers, and laboratory demonstrators. Each of these roles brings technical and teaching support that helps students get the most out of hands-on activities.

Laboratory demonstrators are especially important. They guide students before, during, and after lab sessions. This support helps students connect what they learn in lectures with what happens in the lab. This work reports on the roles and impact of laboratory demonstrators, laboratory managers, and lecturers at the South African university. It focuses on how they help students during physics and chemistry laboratory sessions.

Speaker: Buyisiwe Sondezi (University of Johannesburg, Physics Department, P.O. Box 524, Auckland Park, South Africa, 2006)

16:44 Synchrotron Self-Compton Modelling of Blazars in the SPOTS Survey

The Spectral Energy Distribution (SED) of emission produced by blazars, a sub-class of radio-loud Active Galactic Nuclei (AGN), typically exhibits a double-peaked spectrum. The lower-energy peak is attributed to synchrotron emission from relativistic electrons. The origin of the higher-energy peak remains debated and has been modelled by both leptonic and hadronic processes. In this study, we investigated the leptonic scenario for a selection of TeV detected blazars in the SPOTS (Spectro-Polarimetric Observations of TeV Sources) survey. The JetSet code was used to fit a purely-SSC model to multi-wavelength archival data of the selected blazars. The models can be used to constrain the physical parameters of the emitting region, such as the magnetic field strength and the size of the region. The best fit parameters and SEDs for each source are presented. These results provide the groundwork for our future research, which will focus on the lepto-hadronic scenario in order to put better constraints on the contribution of hadronic emission for these sources.

Speaker: Drianca Reddy

Drianca_Reddy_Flash_Talk.pdf

Drianca_Reddy_Poster.pdf

16:45 Evaluating the Effectiveness of Inquiry-Based Practical Activities in Enhancing Students’ Understanding of Series and Parallel Electrical Circuits

Grounded by constructivism, the study explored students’ understanding of fundamental electrical concepts through hands-on activities involving series and parallel circuits. The study used a pre-post test design to evaluate their conceptual understanding of current, resistance, voltage and the effects of changes in circuits. The evaluation also assessed students’ perceptions of which experiment was most useful to their learning and their comprehension of the aims of scientific inquiry. The results indicated that students were unable to strengthen their knowledge of the characteristics of series and parallel circuits, in particular the relationship between current, voltage and resistance. Most students appreciated that scientific experiments involve scientists conducting experiments to test hypotheses, gather data, and enhance their understanding of natural phenomena. The results indicate that practical experimental tasks enhance their conceptual understanding, improve analytical reasoning and enable meaningful learning in the physical sciences. Empirical enquiries still represent a powerful means to increase scientific literacy and students’ engagement in science education.

Speaker: Buyi Sondezi (University of Johannesburg, Chemical Sciences, P.O. Box 524, Auckland Park, 2006)

HEASA Poster-LN-2026.pdf

16:46 Long-term multi-wavelength monitoring of Be X-ray binaries: tracking decretion disc evolution

Be X-ray binaries (BeXBs) consist of a compact object, in nearly all known cases a neutron star, in orbit around a massive Oe/Be companion that hosts a quasi-Keplerian equatorial decretion disc. This disc is the reservoir from which the compact object accretes, and its geometry, density and dynamical state set the conditions for X-ray outburst triggering, amplitude and recurrence. Despite decades of study, the physical conditions that produce Type II (giant) outbursts and long-term superorbital variability remain unresolved, largely because the disc and the X-ray behaviour are seldom tracked at the same time over the multi-year timescales on which the disc actually evolves.

We are carrying out long-term multi-wavelength monitoring of a sample of BeXBs spanning a wide range of orbital periods, eccentricities and inclinations. The programme combines MeerLICHT optical photometry in six bands (ugrizq), SALT spectroscopy of Hα and other disc diagnostics, and publicly available X-ray monitoring data. Together these trace the structural and thermal evolution of the disc from months to years, so that changes in disc size, density and state, including build-up, warping, precession and dissipation, can be linked causally to accretion episodes and to non-thermal emission from the compact object. The resulting dataset will be used to test theoretical models of disc-driven outbursts and superorbital periodicities. Here I present the study sample and first results.

Speaker: Andries Mathiba (University of Cape Town)

16:47 Possible Transient Gamma-Ray Activity from the Fast-Rotating, Highly Magnetized Ultra-Massive White Dwarf ZTF J1901+1458

We present a search for transient gamma-ray activity from the rapidly rotating, highly magnetized white dwarf ZTF J1901+1458 using Fermi-LAT data. We investigate the temporal behaviour of the source by analysing individual time intervals and identify several candidate episodes with test statistics corresponding approximately to the (3\sigma) significance regime. The candidate intervals show integrated photon fluxes of order (10^{-7})–(10^{-6}) ph cm(^{-2}) s(^{-1}), with the most significant interval reaching approximately 4$\sigma$. However, accounting for the large number of temporal trials substantially reduces the significance of the most significant individual excursion, and we therefore treat these intervals as candidate transient events rather than definitive detections. Nevertheless, the recurrence of candidate episodes motivates investigation of whether such activity could be connected to the extreme physical properties of ZTF J1901+1458, whose rapid rotation and strong magnetic field provide substantial rotational and magnetic energy reservoirs. We therefore investigate an alternative magnetospheric mechanism in which differential rotation generates magnetic stresses and an accelerating electric potential that injects non-thermal particles into the magnetosphere. For the adopted parameters, the model produces an accelerating potential of (\Delta V \simeq 5.53\times10^{11}) V, while a six-hour event requires a free magnetic energy of (\sim9.98\times10^{39}) erg, corresponding to a toroidal-to-poloidal field ratio of (\sim0.098) and a differential-rotation fraction of (\sim3.0\times10^{-4}). Stronger differential winding is expected to enter a nonlinear regime regulated by magnetic back-reaction. The resulting framework provides an alternative interpretation of the candidate gamma-ray activity and enables a self-consistent test of the available magnetic energy, particle acceleration, and subsequent radiative emission.

Speaker: Spencer Tendai Madzime

MadzimeST-Poster2026HEASA.pdf

Thursday 1 October

08:30 → 10:00 Transients 2

Chair: Piet Meintjes

08:30 Gamma-Ray Bursts redshift estimators and the connection between GRB rate and Star Formation rate

Gamma-ray bursts (GRBs) can be probes of the early Universe, but currently, only 26% of GRBs observed by the Neil Gehrels Swift Observatory have known redshifts (z) due to observational limitations. To address this, we estimated the GRB redshift (distance) via a supervised statistical learning model that uses optical afterglow observed by Swift and ground-based telescopes. The inferred redshifts are strongly correlated (a Pearson coefficient of 0.93) with the observed redshifts, thus proving the reliability of this method. The inferred and observed redshifts allow us to estimate the number of GRBs occurring at a given redshift (GRB rate) to be 8.47─9 yr−1 Gpc−1 for 1.9 < z < 2.3. Since GRBs come from the collapse of massive stars, we compared this rate with the star formation rate, highlighting a discrepancy of a factor of 3 at z < 1.

Speaker: Maria Dainotti (Stanford University)

Redshift-ML-Cape-Town-2026-Dainotti-final.pdf

Redshift-ML-Cape-Town-2026-Dainotti-final.pptx

09:01 Deep-Learning-Based FRB Populations Simulation - Zero Order Model

The statistical characterization of Fast Radio Burst (FRB) populations is fundamentally constrained by selection biases and the non-linear coupling of intrinsic source physics with extrinsic propagation effects. A primary hurdle is the DM-z degeneracy, where unknown host galaxy dispersion ($DM_{host}$) obscures cosmological distances. This is further compounded by morphological smearing; multi-path scattering. Consequently, current catalogs provide a biased representation of the underlying population, necessitating a robust framework to disentangle these signatures.

To address these challenges, we implement a computational pipeline that integrates a physical model of FRB emission with a stochastic transport module for the intervening medium, ultimately convolved with a deterministic telescope response function. The first stage of the project establishes a minimal physical model of FRB to define baseline parameter correlations. Subsequent stages will expand this framework by integrating multi-parameter population synthesis tools, such as \texttt{frbpoppy}, alongside more sophisticated models of burst morphology and DM-z relations. The machine learning module is structured as a stochastic inverse mapping of the above mentioned forward-modeled populations.

By employing a Deep Neural Network (DNN) as an estimator, we test the feasibility of recovering intrinsic burst parameters by mapping observables from the detection domain back to the progenitor’s source model parameters. This process requires the network to account for the degenerate effects of the transport medium and the telescope response function. We evaluate the performance of this pipeline in yielding estimations for critical burst parameters by testing it with the CHIME/FRB catalog, providing a preliminary assessment of whether such a framework can reliably constrain intrinsic burst geometry or contribute to the use of FRBs as cosmological probes.

Speakers: Prof. Christo Venter (North-West University), Shruti Bhatporia (North-West University)

HEASA_2026_Sep.pdf

09:14 Probing magnetar central engines in short GRBs through fallback accretion and extended X-ray emission

Short gamma-ray bursts (sGRBs) are associated with compact binary mergers, as established by the joint detection of GW 170817 and GRB 170817A, although the nature of the post-merger remnant remains uncertain. A long-lived millisecond magnetar provides a possible central engine for the extended X-ray emission observed in a fraction of sGRBs. We investigate nine sGRBs detected between 2016 and 2025, selected on the basis of extended emission in the Swift/BAT and XRT light curves, measured redshifts, and a luminosity cut-off of ($10^{52}$) erg/s. We model their extended emission using fallback accretion onto a magnetar coupled to the propeller mechanism. Joint BAT–XRT fits are examined using three energy prescriptions: the XRT (0.3–10 keV) band, BAT (15–50 keV) band, and their native energy bands. The parameters derived from these fits are consistent with predictions for magnetar properties and fallback accretion models with an exception of GRB~231117A. Two events favour the XRT band, three favour the BAT band, while the remaining bursts are better described in their native bands. Using the inferred initial disc masses, we further constrain the progenitor binary parameter space, linking the neutron-star mass ratio and total binary mass through numerical-relativity prescriptions for the remnant disc. We demonstrate that sGRBs with extended emission follow the universal relation akin to other accreting compact objects transitioning from accretion to propeller, with significantly lower radiative efficiencies than the X-ray binaries. Finally, we highlight that future late-time radio follow-ups of kilonova afterglows from these events with MeerKAT and the upcoming SKA, will be crucial for obtaining direct evidence of magnetar central engines in compact binary mergers.

Speaker: Dr ankur ghosh (University of Johannesburg)

HEASA2026.pdf

HEASA2026.pptx

09:27 Optical Spectroscopy and Temporal Evolution of the Nova V1405 Cas

This paper presents the findings from our study of nova V1405 Cas over the first 1051 days after the outburst. The study includes an analysis of the photometric light-curve evolution, along with a detailed spectroscopic analysis. Photometric analysis shows that the nova is a very slow nova, with a decline timescale of t2 ≈ 165 days. The mass of the white dwarf (WD) is calculated as MWD ∼ 0.7 M⊙. The secondary star is a low-mass main-sequence star, with a mass of . Spectral observations show initial dominance of Balmer emission lines accompanied by prominent P Cygni profiles during the first +339 days. These features disappeared in later epochs, being replaced by high-ionization coronal lines, indicating that the nova had transitioned to the coronal phase by day +371. To investigate the physical conditions of the ejecta and the central source, we conducted photoionization modeling using cloudy. Our model reveals a gradual increase in the temperature and luminosity of the system, and suggests that the ejecta were primarily composed of He, N, Fe, Ne, and Ca, with noticeable temporal variations in their relative abundances. The estimated mean ejected mass is approximately 1.10 × 10−4 M⊙, which is relatively high and suggests a low-mass WD. Our optical spectroscopic and photometric analyses, combined with detailed photoionization modeling, indicate that the WD in Nova V1405 Cas is unlikely to be of the ONeMg type.

Speaker: Gesesew Reta Habtie (Debre Berhan University)

09:40 GRB phenomenological relations' dependence on cosmology

Phenomenological relations between the isotropic energy and spectral peak energy in the source rest frame (the Amati relation) and between the isotropic luminosity and spectral peak energy in the source rest frame (the Yonetoku relation) in gamma-ray bursts have been widely conjectured as potential cosmological standard candles. However, reliably using these relations as standard candles requires calibrating them. In this study, we use supernovae data to optimize the parameters of the Amati and Yonetoku relations and show that these parameters depend on the cosmological models.

Speaker: Soebur Razzaque

Razzaque_HEASA2026.pdf

10:00 → 10:30 Coffee Break

10:30 → 11:35 Transients 3 / Multi-Messenger

Chair: Anna Luashvili

10:30 Extending the Cosmic Distance Ladder to High Redshifts with Gamma-Ray Bursts

Gamma-ray bursts (GRBs) can extend cosmological studies beyond the redshift range of Type Ia supernovae (SNe Ia), but their calibration is affected by the circularity problem. We apply LADDER, a deep-learning reconstruction trained on Pantheon+ SNe Ia, to obtain a model-independent distance-redshift relation. Building a self-contained calibration pipeline applied directly to raw Fermi-GBM catalog data, we calibrate both the Amati relation ($E_{\text{p, i}}$-$E_{\text{iso}}$) and Yonetoku relation ($E_{\text{p, i}}$-$L_{\text{iso}}$) without assuming a cosmological model. We then use these calibrated relations to estimate $E_{\text{iso}}$ and $L_{\text{iso}}$ for the Fermi-GBM sample. We further investigate whether the calibrated relations can be inverted to infer GRB pseudo-redshifts, and report on the accuracy, coverage, and current limitations of this inversion, including the intrinsic scatter and extrapolation constraints that bound its reliability at the highest redshifts.

Speaker: Tamador Aldowma (Johannesburg University, Omdurman Islamic University)

Tamador_Aldowma_Extending the Cosmic Distance Ladder to High Redshifts with Gamma-Ray Bursts.pdf

Tamador_Aldowma_Extending the Cosmic Distance Ladder to High Redshifts with Gamma-Ray Bursts.pptx

10:43 The use of simulated spectra for machine learning methods with the Fermi GBM catalogue

Machine learning approaches based on the Fermi GBM catalogue data typically use parameters such as the duration of the bursts, its fluence or flux along with various parameters obtained from spectral fits. These approaches typically ignore the error on the spectral parameters. Yet, these errors also contain information about the GRB. In this work, we use the errors on the spectral parameters to simulate spectra compatible with the GRB observed data. We discuss the advantages of using such an approach in comparison with approaches that ignore the error parameters. In particular, we show how this allows us to study GRBs compatible with various sub-ranges in the spectral parameter space.

Speaker: Saeeda Sajjad (Theoretical Research Institute, Pakistan Academy of Sciences (TRIPAS), Pakistan, Centre for Astro-Particle Physics (CAPP), University of Johannesburg, South Africa)

Presentation_HEASA_Saeeda_Sajjad.pdf

10:56 Multiwavelength Study of the Candidate Neutrino Blazar PKS~0215+015 During the IceCube-220225A Epoch

The flat-spectrum radio quasar PKS~0215+015 ($z \simeq 1.715$) was found to be positionally and temporally coincident with the IceCube neutrino event IceCube-220225A, detected on 25~February~2022 with a reconstructed energy of $\sim$154~TeV. The source was the only $\gamma$-ray emitter within the 90\% neutrino localisation region and was independently confirmed to be in an elevated $\gamma$-ray state at the time of the alert, accompanied by a historic radio outburst and VLBI evidence for a new superluminal jet component. We present a multiwavelength analysis of PKS~0215+015 using \textit{Fermi}-LAT, \textit{Swift}-XRT and \textit{Swift}-UVOT data spanning nearly two decades, and construct the broadband spectral energy distribution (SED) for the flaring epoch coincident with the neutrino detection. The SED is well reproduced by a leptonic model (synchrotron, synchrotron self-Compton and external Compton emission), close to equipartition between the electron and magnetic field energy densities. A co-accelerated hadronic component, explored to assess the maximum neutrino flux allowed by the data, remains radiatively subdominant despite requiring a proton kinetic luminosity roughly two orders of magnitude above equipartition, illustrating the baryon-loading problem common to leptohadronic neutrino-blazar modelling. An independent size estimate from short-term $\gamma$-ray variability agrees closely with the SED-derived emission-region size. We discuss the implications of these results for the plausibility of a physical association between PKS~0215+015 and IceCube-220225A, and for future multimessenger searches involving high-redshift FSRQs.

Speaker: Athira M Bharathan (North-West University, South Africa)

AMB_HEASA2026.pdf

AMB_HEASA2026.pptx

11:09 Multi-frequency views of high-redshift dark matter halos

Indirect dark matter searches have historically concentrated on the nearby universe. In this work we explore whether higher redshift objects $z \gtrsim 0.1$ could be an under-utilised resource in the search for the fundamental nature of dark matter. We do so by exploring MeerKAT observations of higher redshift galaxy clusters and considering current and future gamma-ray experiment sensitivities to emissions from these objects. Our results indicate that individual distant galaxy clusters offer somewhat competitive limits. However, their true value may be in the large number of these objects, allowing a large-scale joint analysis.

Speaker: Geoff Beck

dark_matter_heasa_2026.pdf

11:22 Probing Dark Matter-Photon Interactions with High Energy Gamma-Ray Observations

High-energy astrophysical messengers provide a unique probe of possible non-gravitational interactions of dark matter. In particular, gamma rays produced in the vicinity of supermassive black holes may traverse large dark-matter column densities, especially in the presence of dense dark-matter spikes, and can consequently be attenuated through dark matter–photon scattering. In this work, we develop a statistical framework to constrain dark matter–photon interactions directly from gamma-ray observations, extending our recent analysis of dark matter–neutrino scattering to the photon sector. The modification of the source flux induced by propagation through the dark-matter distribution is incorporated into the predicted gamma-ray signal and confronted with observational data through a likelihood-based analysis. This enables
statistically well-defined constraints on the dark matter–photon scattering cross section and allows information from multiple astrophysical sources to be combined. We investigate the dependence of the sensitivity on the dark-matter mass and astrophysical dark-matter distribution, including the enhanced densities expected around central
supermassive black holes. Our analysis provides a complementary, data-driven probe of dark matter–photon interactions and demonstrates the broader potential of high energy multimessenger observations to probe dark matter signatures.

Speaker: Khushboo Dixit

K_Dixit_HEASA_2026.pdf

K_Dixit_HEASA_2026.pptx

11:35 → 12:30 Luch Break

12:30 → 17:30 Excursions

18:00 → 20:00 Braai: Conference Dinner

Friday 2 October

09:00 → 10:05 X-Ray / Gamma-Ray Binaries / Instrumentation

Chair: Hartmut Winkler

09:00 Positron escape from dark matter spikes in black hole X-ray binaries

The anomalously fast orbital decay of the black hole X-ray binaries A0620−00 and XTE J1118+480 has been attributed to dynamical friction in dark matter density spikes, and annihilation within these spikes has recently been proposed as the origin of the high-energy positron excess measured by AMS-02. That proposal treats positron propagation using interstellar conditions throughout, neglecting the environment close to the black hole. In this work, we use equipartition estimates of the accretion-flow magnetic field, calibrated to these two systems, to test whether that region can safely be neglected. We show that it cannot: synchrotron losses in the near-horizon field allow only a small fraction of a percent of the positrons to escape, weakening the predicted flux by more than three orders of magnitude. We further show that the spike is limited by its own annihilation, suppressing the source independently of the magnetic field. Either effect alone is sufficient to remove the proposed explanation. We conclude by discussing what the same environment implies for the use of these binaries as dark matter targets.

Speaker: Mpho Kgoadi (University of the Witwatersrand)

Mpho_Kgoadi_Heasa_Presentation.pdf

09:13 Super-Eddington accretion and the formation of the massive neutron stars

Accretion onto the first-born neutron star during a super-Eddington episode has been proposed as one of the formation channels of the most massive neutron stars in the gravitational-wave catalogue, notably the components of GW190425. In this work, we examine the transfer of material from the outer disc to the stellar surface during the super-Eddington phase. We take into account the disc truncation at the magnetospheric radius and radiatively driven winds. The magnetic moment, spin and baryonic mass of the neutron star are evolved as a coupled system, incorporating accretion-induced field burial and Ohmic re-emergence, with baryonic mass converted to gravitational mass along the track. The retained fraction that emerges depends on the disc wind index, the magnetic moment, the mass-transfer rate and the spin period, and we map this dependence across the plausible parameter space. We test our results against the mass–spin distribution of Galactic recycled pulsars and the gravitational-wave mass measurements.

Speaker: Dr Lutendo Nyadzani (University of Johannesburg)

Lutendo_HEASA_2026.pdf

09:26 On the recent multiwavelength results of outbursting Be X-ray binaries

Be X-ray binaries, which constitute the largest subclass of high-mass X-ray binary systems, consist of a neutron star in an eccentric orbit around a Be star companion, accompanied by a geometrically thin Keplerian disc. These systems are strong candidates for being progenitors of gravitational waves, as their evolutionary process can ultimately lead to the formation of a binary system containing two compact objects (either two neutron stars or a neutron star and a black hole). The interaction between the neutron star and the Be disc results in the accretion of matter, which leads to X-ray outbursts.

These X-ray outbursts occur in two varieties: Type I (normal outbursts, with luminosities less than 10^37 erg/s) and Type II (giant outbursts, with luminosities greater than 10^37 erg/s). The variability of the disc can be traced through the changes in the Balmer emission lines in the optical spectra, with the Hα emission line being the strongest and best studied.

In this presentation, I will share the optical and X-ray analysis of individual outbursting systems monitored with the Southern African Large Telescope (SALT), OGLE, MeerKAT, and X-ray missions such as Swift and MAXI. The aim is to study the impact of the neutron star on the Be disc under various orbital configurations and environmental conditions. I will discuss the interesting long-term behavior of the Balmer lines over multiple orbits of the neutron star and draw conclusions about the structure of the Be disc. Additionally, I will highlight the differences in behavior among the systems and how variations in the orbital parameters affect the evolution of the Be disc and the accretion process, leading to enhanced X-ray emission.

Speaker: Itumeleng Monageng

Itumeleng_Monageng_HEASA2026.pdf

Itumeleng_Monageng_HEASA2026.pptx

09:39 Einstein Probe: Exploring the Dynamic X-ray Universe

The study of the dynamic Universe is entering a new era of time-domain, multi-wavelength and multi-messenger astronomy. High-energy transients provide unique probes of black-hole accretion, compact objects, stellar explosions and the early Universe, while electromagnetic counterparts to gravitational-wave and neutrino events offer new opportunities for understanding the most energetic cosmic phenomena. The Einstein Probe (EP) is a Chinese space mission designed to explore this largely uncharted transient X-ray sky with unprecedented sensitivity and monitoring cadence. Its Wide-field X-ray Telescope (WXT) employs novel lobster-eye micro-pore optics to provide a field of view of approximately 3600 square degrees in the 0.5–4 keV band, with a sensitivity more than an order of magnitude better than previous wide-field X-ray monitors. A complementary Follow-up X-ray Telescope (FXT), operating over 0.3–10 keV, enables rapid characterization and accurate localization of newly discovered sources. EP is designed to discover and monitor a wide range of transient and variable phenomena, including tidal disruption events, gamma-ray bursts, supernova shock breakouts, magnetars, X-ray binaries and stellar flares, as well as electromagnetic counterparts of gravitational-wave events. Its combination of wide-field monitoring, high sensitivity and rapid follow-up opens a powerful new window on the variable X-ray Universe.

Speaker: David Buckley (South African Astronomical Observatory)

Buckley-EinsteinProbe.pptx

09:52 Assessing the Fringe Detectability of the Africa Millimetre Telescope for Event Horizon Telescope Observations

The Africa Millimetre Telescope (AMT), planned for construction in Namibia, will expand Africa’s contribution to millimetre very-long-baseline interferometry (VLBI) and the Event Horizon Telescope (EHT), supporting future EHT and multi-wavelength studies of supermassive black holes, accretion flows, and relativistic jets. Its ability to participate effectively in EHT observations will depend on both the sensitivity of the telescope and the stability of the atmosphere above the observing site. In this study, we assess the expected fringe detectability of the AMT with ALMA and NOEMA at 230 GHz for observations of Sgr A and M87. The sensitivity of the AMT is estimated using atmospheric and site conditions measured in situ at the candidate sites, together with models of atmospheric opacity, system temperature, and antenna performance. These estimates are combined with ALMA and NOEMA SEFDs derived from EHT system-temperature and gain calibration data to determine the expected signal-to-noise ratio of the corresponding VLBI baselines, providing a direct measure of the detectability and reliability of the correlated fringes. Atmospheric coherence times at the AMT candidate sites are estimated using phase-monitoring stations developed at Radboud University. To calibrate these instruments, measurements from a Radboud phase monitor installed at the IRAM Plateau de Bure site are compared with those from the established IRAM phase-monitoring system at the same site. The resulting relationship was then be applied to the phase-monitoring stations operating at the candidate AMT sites in Namibia. By combining station sensitivity, atmospheric coherence time, source visibility, and expected source flux, we aim to determine the periods during which useful fringes are most likely to be detected.

Speaker: Hiiko Katjaita (University of Namibia)

HEASA_2026_AMT_Fringe_Detectability.pdf

HEASA_2026_AMT_Fringe_Detectability.pptx

10:05 → 10:30 Coffee Break

10:30 → 12:05 Other High-Energy Sources 1

Chair: Michael Backes

10:30 Resonant Pacemakers — Heartthrob of Sgr A emission*

This talk proposes using resonant structures around a Kerr black hole as a model agnostic means of quantifying departures from the Kerr Metric. Initial observational evidence that these structure exist around Sgr A* is presented.

When a black hole is immersed into an astrophysical environment, the KAM theorem predicts that the spacetime geodesic structure will exhibit non-smooth departures from Kerr metric in regions where orbital resonances occur. I quantify the locations of resonant orbits and associated characteristic timescales. A preliminary survey of the published observational results for Sgr A reveals that all the statistical ’pacemaker’ frequencies identified by Leibowitz in X-ray and near-IR flaring activity can be associated with resonant structures if Sgr A has a dimensionless spin value near a ∼ 0.5.

Hotspots around Sgr A observed by the EHT and flares resolved by the GRAVITY experiment can be associated with region in which orbital resonances occur, providing an explanation for their origin as well as a mechanism rendering them stable.
It is thus proposed that some of the observed variability in the radiation emitted from Sgr A may result from interactions between inspiralling compact objects, the accretion disk and low order resonant structures found around the black hole. The Galactic speed trap and Galactic fish and release flare models are introduced as paradigms for discussing these interactions. We remark on the coincidence that the chronology of three flare dates recorded by the GRAVITY collaboration in 2018 nominally passes the Galactic Speed trap test. Noting that the dates at which the flares occur is consistent with timing of emission triggered by the resonant passage of a single intermediate mass ratio inspiralling object transiting a succession of resonant locations found in the regions to which polarization and astrometric data confine the emission.

Speaker: Dr Jeandrew Brink (University of the Free State)

Heasa2026.pdf

11:01 Modelling the Radio Flux Densities of Dwarf Novae Outbursts Detected by MeerKAT

Using multiple theoretical emission models, the flux density of dwarf novae can be modelled. These sources can emit light from radio frequencies up to x-ray frequencies. Using various theoretical models, we can gain insight on the parameters of these sources. For this study, RU Pegasi, IP Pegasi, and V426 Ophiuchi were selected as they were detected by the MeerKAT telescope during outburst. Following on the work presented at the previous HEASA conference (HEASA2025), the radio fluxes of these sources were modelled using the Van der Laan model, estimating the magnetic field strength, electron energies, number density of the electrons, and the sizes of expanding relativistic blobs. The models show parameters within a reasonable range for the detected radio fluxes. Theoretical models allow us to estimate key details about the source, such as the temperature of the source, the size and temperature of the emitting regions, as well as the magnetic fields contained in these sources. The optical and x-ray emission of Ru Pegasi and V426 Ophiuchi showed good fits for the black body and bremsstrahlung, whereas RU Pegasi only has a decent blackbody fit.

Speaker: Keith McPherson

Keith HEASA 2026 Final.pptx

11:14 Search for Pulsed Emissions from V1223 Sagittarii in Fermi-LAT and TESS data

V1223 Sagittarii is an intermediate polar (IP), a subclass of magnetic cataclysmic variables containing an accreting white dwarf(WD) with a magnetic fields ranging between(0.5-8) MG. Optical and x-ray observations have established an orbital period of approximately 3.366 hr and a WD spin period of approximately 12.4 min. Additionally, a 13.2 min beat period, arising from the interaction between the spin and orbital frequencies, has been detected and is often the more dominant optical period. V1223 Sagittarii have been investigated as a source for non thermal emission and high-energy particle acceleration, with theoretical evidence for high-energy emission.Recent exploratory searches for $\gamma$-ray emission from highly magnetised white dwarfs using approximately 15 years of Fermi-LAT data, resulted in indications of probable transient pulsed emissions. V1223 Sagittarii were among the sources looked at and showed signs of transient emission but no dedicated periodicity search were done for this source. In this study we conducted a follow up analysis using a longer base line of about 18 years of Fermi-LAT data in conjunction with 3(120s resolution), and 1(20s resolution) observations sections of TESS data. Analysis techniques used with Fermi-data includes unbinned light curves and TS-Gating. Periodicity search were done using Rayleigh and H-test algorithm using previously published ephemeris. Timing analysis of TESS data were done using the \textit{lightkurve} module in python utilizing the Lomb-Scargle Periodogram.Prelimanary results shows pulsed emission from V1223 Sagittarii in the Fermi data and also confirmed in TESS data, ongoing analysis will be to better constrain the ephemeris used for Periodity search using a extended dataset which includes BOOTES6 and 7 data.

Speaker: Mr Erik Van Vuuren (University of the Freestate)

Erik_v_vuuren_Heasa_presentation.pdf

11:27 The MeerKAT-South Pole Telescope 800 square degree Survey

I will present an overview and report early science from the MeerKAT-South Pole Telescope (SPT) Survey, a deep MeerKAT UHF-band eXtra Large Project (XLP) legacy project recently approved to map 800 square degrees of the southern sky to a sensitivity of ~10 uJy/beam. Uniquely designed to exploit the synergy between world-leading observatories at ~1 GHz and ~100 GHz, this survey covers the deepest Cosmic Microwave Background fields in existence. In this talk, I’ll focus on early results from the survey’s first stage: a 100 square degree pilot that has already detected ~300,000 radio sources. I will highlight specific results demonstrating the strong synergy between these cm- and mm-wave telescopes, including the identification of high-redshift (z > 6) dusty star-forming galaxies, radio halos in SZ-selected galaxy clusters, and the discovery of rare phenomena like Odd Radio Circles, X-shaped radio galaxies, high-redshift OH megamasers and Long-Period Transients. Ultimately, this survey will serve as a significant pathfinder for SKA-era galaxy evolution and cosmology, with commensal image-domain transient science. Furthermore, it will provide significant radio legacy value to complement upcoming multi-wavelength campaigns with LSST, Euclid, and the Simons Observatory.

Speaker: Prof. Roger Deane (IDIA / University of Cape Town)

Deane-MK-SPT-12minOverview-HEASA.pdf

11:40 Probing Magnetic Reconnection as a Mechanism for Recurrent GeV $\gamma$-Ray Emission in the Intermediate Polar V1674 Her

We present a reanalysis of the \textit{Fermi}-LAT data of V1674 Her, a rapidly rotating intermediate polar with GeV $\gamma$-ray emission first detected during its 2021 nova outburst. Previous interpretations of the $\gamma$-ray emission from V1674 Her have primarily invoked particle acceleration in shocks associated with the nova ejecta. Here, we investigate the temporal and spectral properties of the $\gamma$-ray emission and explore magnetic reconnection as an alternative particle-acceleration mechanism. We perform a deep periodicity search of the \textit{Fermi}-LAT data at both the white-dwarf spin period and the binary orbital period to investigate possible modulation of the $\gamma$-ray emission by the characteristic timescales of the system. In addition, using the $\gamma$-ray activity observed during the 2021 nova outburst as a reference, we conduct a systematic search for similar transient enhancements throughout the full \textit{Fermi}-LAT data set. Several candidate episodes of enhanced $\gamma$-ray emission are identified, although at lower statistical significance than the 2021 event, suggesting that V1674 Her may exhibit recurrent episodes of high-energy activity. We further perform broadband spectral analysis using Power-Law, Log-Parabola, and PLSuperExpCutoff2 models. Among the models considered, the Log-Parabola provides the preferred description of the $\gamma$-ray spectrum, indicating spectral curvature that is not adequately described by a simple Power-Law model. The combination of spectral curvature and recurrent transient activity provides additional constraints on the physical origin of the $\gamma$-ray emission. We interpret these results within a magnetic-reconnection framework in which interactions between the magnetic field of the rapidly rotating white dwarf and the surrounding accretion flow can trigger reconnection and generate strong electric fields capable of accelerating particles to relativistic energies. The resulting non-thermal particles can produce GeV $\gamma$-rays through hadronic channels. We investigate whether this mechanism can reproduce the observed spectral shape and account for the recurrent episodes of enhanced $\gamma$-ray activity in V1674 Her. This provides a physically motivated alternative to shock-driven particle acceleration and offers a framework for understanding high-energy emission from intermediate polars.

Speaker: Spencer Tendai Madzime (University of the Free State)

MadzimeST-HEASA2026.pdf

11:53 Magnetic Regulation and Energetic Stellar Feedback in Massive Galactic Star-Forming Regions

Energetic feedback from massive young stars can modify the same magnetic structures that regulate gravitational collapse, yet the observational connection between feedback-driven magnetic restructuring and star-formation efficiency (SFE) remains poorly constrained. We investigate 11 high-mass Galactic star-forming regions observed with the James Clerk Maxwell Telescope (JCMT), combining plane-of-sky magnetic-field strength, magnetic morphology, normalized mass-to-flux ratio, magnetic criticality, SFE, and published evidence for feedback–magnetic-field interaction. Magnetic-field strengths span 138.83 – 3364.93 μG, while 10 of the 11 regions (90.9%) are magnetically supercritical, indicating that gravitational collapse can proceed despite moderate-to-strong fields. Magnetic-field strength shows only a weak, statistically insignificant relation with SFE (ρ=-0.191), (p=0.573), while the mass-to-flux ratio exhibits a stronger but non-significant association (ρ=-0.419), (p=0.199). Source-by-source polarization studies reveal direct observational evidence of feedback-driven magnetic-field restructuring in four regions and suggestive evidence in three additional sources, including field alignment with outflow cavities, shock-related distortion, and reorientation by ionized or explosive feedback. Regions with direct feedback–magnetic interaction have a median SFE of 0.00721, compared with 0.0375 for sources in which such interaction is not observationally established. Although the small sample precludes a causal interpretation, the result provides a direct observational link between feedback environment, magnetic-field response, and star-formation activity. The findings favour a coupled evolutionary framework in which gravitational collapse proceeds predominantly in supercritical magnetized gas, stellar feedback subsequently reshapes the magnetic environment, and the resulting star-formation efficiency reflects the combined action of gravity, magnetic regulation, and energetic feedback rather than magnetic-field strength alone.

Speaker: PATRICK OKEZUONU (ABIA STATE UNIVERSITY, UTURU)

12:05 → 13:00 Lunch break

13:00 → 14:20 Other High-Energy Sources 2 / AGN 4 / Education and Outreach 1

Chair: Geoff Beck

13:00 CM Microscopii: an ER UMa-type dwarf nova with a permanent-superhumper standstill

Accretion discs experience various kinds of instabilities, observed as energetic events in our Universe. Compact binaries especially offer a unique opportunity to study these instabilities as transient phenomena. Here we report optical studies of the cataclysmic variable CM Mic, characterized by highly frequent dwarf nova outbursts driven by thermal-viscous instability and occasional standstills in between. Our observations newly established its orbital period and mass ratio as 0.077059(3) d and 0.17(1), respectively. These values agree with standard binary evolution models of cataclysmic variables. Nevertheless, its short outburst cycles imply that its mass-transfer rate must be an order of magnitude higher than those of systems with similar orbital periods. We further find that CM Mic shows positive superhumps, driven by tidal instability, during both its dwarf nova outbursts and standstills. This makes CM Mic a unique laboratory for directly comparing superhump properties in outburst and standstill. The alternation between the standstill and dwarf nova states in CM Mic implies a change in its mass-transfer rate by a factor of 1.05--1.4 near the critical value. Overall, these findings establish CM Mic as an important laboratory for studying a tidally unstable disc around the critical mass-transfer rate.

Speaker: Yusuke Tampo (South African Astronomical Observatory)

YTampo_HEASA2026

13:13 The X-ray and optical emission of the intermediate polar Swift J0614.0+1709

Attached.

Speaker: Nikita Rawat (South African Astronomical Observatory)

Nikita_HEASA.pptx

13:26 Frequency- and timescale-dependent variability of ALMA blazar calibrators

We present initial efforts towards the construction of a catalogue of frequency- and timescale-dependent variability properties of blazars observed as flux calibrators with the Atacama Large Millimeter/submillimeter Array (ALMA), exploiting multi-epoch observations spanning Bands 3–10. Multi-epoch light curves are constructed for suitably sampled sources, from which complementary variability diagnostics, including the modulation index, fractional variability amplitude, de-biased variability index, full flux-density range, and χ²-based tests of a constant-flux hypothesis, are derived while accounting for measurement and calibration uncertainties. Particular emphasis is placed on ALMA Bands 3, 6, and 7, which correspond to observing bands planned for the future Africa Millimetre Telescope (AMT) in Namibia. The resulting catalogue is intended to provide a homogeneous reference set of millimetre/submillimetre blazar variability measurements and to identify well-characterised sources for future monitoring and variability studies with the AMT. More broadly, this work establishes a statistical baseline for interpreting AMT observations of relativistic jets and contribute to the development of time-domain blazar science with the AMT.

Speaker: Eli Kasai (University of Namibia)

#3Eli_HEASA_2026.pdf

13:39 Multi-Domain Blazar Modelling with B13

In this work, we demonstrate the application of the Gammapy Python package for simultaneous multi-wavelength spectral fitting of low level data across multiple energy decades. We have integrated the B13 lepto-hadronic emission code into the Gammapy framework, enabling comprehensive multi-instrument data analysis. Additionally, we incorporate IceCube neutrino detector response functions based on publicly available effective areas and point-spread functions and energy dispersion matrices from the "All-sky point-source IceCube data: years 2008-2018" dataset. This allows a self consistent way to constrain model parameters through neutrino flux predictions or limits. Including neutrino data in our approach grants us the ability to assess the viability of different jet composition scenarios based on a comparison between neutrino count expectation and detection.

Speaker: Joshua Robinson (North-West University)

Multi_DomainBlazarModellingwithB13v2.pdf

13:52 Spectro-Polarimetric Observations of TeV Sources (SPOTS): Results and updates

Blazars are a subclass of Active Galactic Nuclei (AGN) that contain relativistic jets oriented towards the observer. The Spectral Energy Distribution (SED) of these sources are typically dominated by two broad non-thermal components. The lower-energy component is produced by synchrotron emission from relativistic electrons in the jet, while the high-energy component can be a combination of inverse Compton scattering and hadronic processes. Certain blazars contain an additional underlying thermal component at optical/ultraviolet wavelengths that can be difficult to disentangle from the non-thermal emission. Despite the current knowledge of these sources, several aspects are not fully understood, including the underlying magnetic field geometry, particle acceleration mechanisms, and the exact contributions of different emission processes. In addition to multi-wavelength observations, polarization measurements of these sources can provide critical insights to constrain some of their properties. In this study, we present results from the Spectro-Polarimetric Observations of TeV Sources (SPOTS) campaign. The results include optical spectro-polarimetric observations of 14 TeV-emitting blazars using the Southern African Large Telescope (SALT). Overall, observations of the sample during this campaign showed a low average optical polarization (Π<10%). A few sources exhibited smooth angle rotations on time scales of days to weeks, while most others showed stochastic variations consistent with turbulent magnetic fields. The average ordering of the magnetic field was modelled for each source and found to be generally low, consistent with emission arising in extended, turbulent regions of the jet. For individual sources, correlations between polarization and its frequency dependence were found. The nature of the frequency dependence varied across observations, indicating that simple one-zone models are insufficient to describe the sources and that FB must be wavelength-dependent. The future of the study will combine the polarization measurements with multi-wavelength data in order to model the SEDs of these sources.

Speaker: Izak van der Westhuizen

HEASA2026_vdWesthuizen.pptx

14:05 Astronomy for a Better World!

For over a century, the International Astronomical Union (IAU) has promoted and safeguarded astronomy worldwide through its Office of Astronomy for Development (OAD), hosted in South Africa by the National Research Foundation (NRF) and supported by the South African Department of Science, Technology, and Innovation (DSTI). The OAD has established a network of 11 regional offices globally and pursues a bold vision: astronomy for a better world. This talk discusses the work of the OAD, which has awarded over €1.5 million in grants to 254 projects, reaching over 2 million people in 113 countries by mobilising astronomy as a tool for human development. We outline the OAD's annual Call for Proposals and the OAD's evolving partnership model, before turning to three flagship programmes that translate astronomy into tangible impact: Astrotourism, which links dark skies and heritage to economic growth and cultural preservation; Astronomy for Mental Health, which harnesses awe and perspective to expand access to wellbeing support; and Astronomy Skills for Development, anchored by the Hack4dev data-science hackathon initiative that builds technical capacity across communities. Drawing on projects spanning access and gender equity to skills training and socio-economic development, we show why astronomy for development is ultimately about people, not just the stars, and how you can get involved.

Beyond programme implementation, the OAD’s growing body of global practice has created important opportunities for research. Evidence generated through projects, partnerships, and regional networks is increasingly informing questions around impact evaluation, science engagement, capacity development, innovation ecosystems, and the role of scientific knowledge in society. This has contributed to the emergence of astronomy for development, and more broadly, science for development, as a developing interdisciplinary research field that connects the physical sciences with development studies, policy, education, and social science methodologies.

By positioning science, and astronomy as a powerful exemplar, within the broader development landscape, this work demonstrates its potential as a cross-cutting, interdisciplinary tool capable of contributing meaningfully to sustainable and inclusive development.

Speakers: Charles Takalana (IAU-OAD), Dr Joyful Mdhluli (IAU-OAD)

Astronomy for a Better World!.pdf

Astronomy for a Better World!.pdf

Astronomy for a Better World!.pptx

14:20 → 14:50 Coffee Break

15:00 → 16:30 Education and Outreach 2 / Pulsars and PWNe

Chair: Eli Kasai

15:00 Effects of Teaching and Learning Atmospheres in the Understanding of Physics Concepts

Friendly learning environments have been widely explored for their potential to enhance students’ understanding of fundamental Physics concepts and improve cognitive achievement. This is particularly significant given the widespread perception of Physics as a challenging subject, especially among first-year university students. During this critical transition period, many students encounter misconceptions and conceptual difficulties that can hinder their academic success.
To address these challenges, lecturers continuously seek effective teaching strategies that make Physics more accessible, engaging, and manageable for students. In this context, a supportive and student-centred learning environment grounded in the pedagogy of care was investigated. The study aimed to determine the impact of such an environment on first-year students’ learning experiences, with a particular focus on enhancing their motivation, participation, conceptual understanding, and sense of ownership of the learning process.
The learning environment was established through a triadic engagement approach that deliberately fostered interactions between lecturer and content, lecturer and students, students and content, and among students themselves. This integrated strategy promoted active participation and deeper engagement with Physics concepts, ultimately leading to improved learning outcomes.
Student performance was monitored over three consecutive years, with the findings demonstrating consistent positive results. These outcomes provide strong evidence of the effectiveness of the approach in improving student learning and supporting success in introductory Physics courses.

Speaker: Prof. Buyi Sondezi (Rare Earth-Based Oxides and Nano Group, Department of Physics, University of Johannesburg, Cnr Kingsway Avenue and University Road, Auckland Park 2006, South Africa)

15:13 Coordinating Astronomy Outreach Across Africa: Opportunities, Challenges and Lessons Learned

Astronomy has a unique ability to inspire curiosity, strengthen scientific literacy, and engage diverse audiences across cultures and generations. While many outreach initiatives are implemented at local or national levels, coordinating science communication at a continental scale presents both unique opportunities and significant challenges.

The African Astronomical Society (AfAS), as the professional body representing astronomy across Africa, has increasingly positioned science communication and public engagement as central pillars of its mission to advance astronomy on the continent. Through partnerships with national institutions, universities, international organisations, and local communities, AfAS has supported and coordinated a diverse portfolio of outreach and education activities, including school engagement programmes, teacher development initiatives, public discussions, citizen science activities, continental awareness campaigns, science communication workshops, and digital engagement.

This presentation reflects on AfAS's experience in designing and coordinating these initiatives across diverse cultural, linguistic, and institutional contexts. Using recent activities as case studies including outreach programmes associated with the AfAS Annual Conference, Africa Day celebrations, public engagement campaigns, Hack4Dev training initiatives, and collaborative partnerships, the presentation will examine practical approaches to building inclusive and sustainable astronomy outreach programmes that reach audiences across the continent.

Beyond showcasing successful initiatives, the presentation will discuss the lessons learned in coordinating continental science communication, including partnership development, stakeholder engagement, digital communication strategies, volunteer mobilisation, and measuring impact. It will also explore the role of continental scientific societies in strengthening public engagement, supporting Astronomy for Development, and fostering a more connected and inclusive African astronomy community.

By sharing these experiences, the presentation aims to contribute practical insights for researchers, educators, outreach practitioners, and scientific organisations interested in expanding the reach and societal impact of astronomy through collaborative science communication.

Speaker: Meryem Guennoun (African Astronomical Society)

AfASslides_HEASA2026.pptx

15:26 Modelling the High-Energy Emission of the Vela Pulsar: A Curvature Radiation Model as a Step Towards Synchro-Curvature Radiation

We model curvature radiation from primary particles accelerated in a dissipative magnetosphere, within an extended separatrix region leading into the current sheet outside the light cylinder, using the azimuthally-dependent electric field from global magnetospheric simulations. This serves as a step towards a full synchro-curvature treatment of the Vela pulsar's high-energy emission observed by H.E.S.S. II (up to ~100 GeV) and the Fermi Large Area Telescope. Unlike synchro-curvature radiation, curvature radiation assumes particles move strictly along field lines, neglecting the additional pitch-angle (synchrotron-like) component that develops in the current sheet (Harding et al. 2021). We compute energy-dependent light curves and phase-resolved spectra, and assess how well this curvature-only model reproduces the observed trends, i.e., the decreasing flux of the first peak relative to the second, the evolving bridge emission, the near-constant peak phases, and the narrowing of pulses with energy. We are extending our model to include synchro-curvature radiation, using this curvature-only treatment as a baseline against which the impact of the additional synchrotron-like component can be assessed.

Speaker: Dr Monica Barnard (Centre for Space Research, North-West University, Potchefstroom 2520, South Africa)

Comparitive_study_of_Vela_MBarnard.pptx

15:39 Optimising Frequency Resolution for Precision Pulsar Timing at Low Radio Frequencies

Pulsars provide exceptionally stable astrophysical clocks, but precision timing at low radio frequencies is complicated by changes in their observed pulse profiles across the observing band. Such frequency-dependent profile evolution can introduce systematic offsets in measured pulse arrival times if a single frequency-averaged template is used. We investigate how frequency resolution can be optimised to mitigate these effects using realistic simulated observations spanning 300–500 MHz, representative of uGMRT Band-3 data. Our simulations incorporate several forms of frequency-dependent pulse-shape evolution, including changes in pulse width, component separation, and relative component amplitudes. We compare pulse arrival times obtained using fully frequency-resolved templates with those derived from progressively finer frequency-averaged subbands, and use statistical model-selection tests to determine when additional frequency-dependent timing corrections are required. We find that frequency-resolved templates naturally account for the evolving pulse shape, while frequency-averaged templates require an appropriate number of subbands to minimise residual frequency-dependent timing structure. In the representative simulation, this transition occurs at 64 subbands across the 200-MHz band. Our results demonstrate that statistically motivated template construction and subband selection can improve the reliability and precision of low-frequency pulsar timing, with broader implications for pulsars as precision astrophysical clocks.

Speaker: Dr Debabrata Deb (Centre for Space Research, North-West University)

15:52 Very-high-energy Pulsar Visibility

Recent detections of pulsed very-high-energy (VHE) emission from PSR B1706−44, Geminga, the Crab, and Vela by ground-based Cherenkov telescopes have prompted renewed efforts to refine models of high-energy pulsar emission. Of particular interest is the discovery of a distinct TeV spectral component in Vela, separate from its GeV component and unlike the spectral behaviour observed in other sub-TeV pulsars. This raises the question of which pulsars may be detectable at TeV energies with current and next-generation Cherenkov telescopes. We investigate this question within the synchro-curvature radiation/inverse Compton (SCR-IC) framework. In this model, primary particles with Lorentz factors of order 5e7 produce the pulsed GeV emission through SCR near the current sheet beyond the light cylinder. These same particles can inverse-Compton scatter optical-to-near-infrared and X-ray photons produced by synchrotron emission from secondary pairs, generating a distinct TeV spectral component. We adopt a three-step approach. First, we develop a TeV visibility metric within the SCR-IC framework. Second, we test the metric using a simplified spectral model to explore the relevant parameter space and identify the physical drivers of TeV detectability. Third, we calibrate and validate these results with our full three-dimensional radiation code, which incorporates primary and secondary-pair injection, realistic magnetic and electric fields, particle dynamics, radiation processes, and relativistic beaming. This framework provides a physically motivated means of assessing TeV pulsar visibility and identifying promising targets for current and future Cherenkov telescopes.

Speaker: Christo Venter

Venter_HEASA.pdf

Venter_HEASA.pptx

16:05 Core and cone radio beam geometry for $\gamma$-ray pulsars under a force-free magnetosphere

Radio emission from pulsars is commonly modelled as a core and cone beam, since this decomposition reasonably reproduces the single, double, and multiple-component pulse profiles observed across the pulsar population, unlike a simple single-beam model. This structure is usually modelled within a vacuum dipole magnetic field. However, this is inconsistent with the more modern force-free magnetosphere, where plasma-filled conditions alter the global magnetic field structure and the geometry of the open field line region, changing the size and location of the core and cone components. In this work, we implement the core and cone beam geometry assuming a force-free magnetosphere. We perform a study to simulate radio light curves and constrain the core and cone beam widths and their relative luminosity, along with the magnetic inclination angle and observer angle for a sample of young pulsars. The goal is to test whether the core and cone geometry reproduces observed pulse shapes and to eventually incorporate it in dual-band light curve fits that also include gamma-ray light curves. We will lastly use these light curve fits to uncover trends across a population of bright, radio-loud Fermi LAT $\gamma$-ray pulsars.

Speaker: Ms Dimakatso Maheso

DJ_Maheso.pdf

16:18 Millisecond pulsars as accelerometers: a search for intermediate-mass black holes along 83 southern sightlines.

Intermediate-mass black holes, spanning 10²–10⁵ solar masses, are the missing link between stellar-mass and supermassive black holes, and no unambiguous example is known in the Milky Way. We search for intermediate-mass black holes along 83 southern sightlines, using the MeerKAT Pulsar Timing Array 4.5-year data release as an array of independent accelerometers. A free-floating IMBH near a pulsar reveals itself not through gravitational radiation, which at these masses lies far below pulsar timing array sensitivity, but kinematically, through the acceleration it imparts. We identify the binary orbital period derivative as the sensitive channel and present anomalous line-of-sight accelerations for the MPTA binaries, together with preliminary exclusion regions in the mass–separation plane.

Speaker: Luyanda Mazwi (University of Johannesburg (Centre for Astro-Particle Physics))

mazwi_mpta.pdf

16:30 → 16:50 Closing Remarks

17:15 → 18:45 SA-GAMMA Executive Committee