CTA Status

• Gavin Rowell (School of Physical Sciences, University of Adelaide)

I will present an update on the status of CTA.

Towards CTAO's 1st Science Data Challenge

• Sabrina Einecke (The University of Adelaide, Australia)

CTAO's first Science Data Challenge (SDC) us currently in preparation. It will provide simulated science-ready (DL3) data products of a complex and realistic gamma-ray sky. The main objectives are to enable a broad scientific community to become familiar with the CTAO data products and scientific analysis tools, to serve as a test bed to for driving forward new algorithms and to verify processes. As a secondee of the SDC technical team, I'm preparing the observation schedule in correspondence with the different science group leaders. In this talk, I will introduce the SDC and give an overview of the science to be simulated.

CTA-Pol update: Plans and Designs

• Nick Tothill (Western Sydney University)

Optical polarimetry is an identified area in which Australia can contribute to CTA. We are planning to construct a prototype polarimeter to be installed on one or more Australian optical telescopes. I will summarise the rationale for the project, give an update on our progress on potential telescope collaborators, and discuss the design process for the instrument.

Investigating a Stereo Trigger in a Small IACT Array

• Simon Lee (School of Physical Sciences, University of Adelaide)

An Imaging Air Cherenkov Telescope (IACT) site in Australia, as part of a worldwide network of IACTs, would be crucial for achieving 24-hour all-sky coverage of the GeV to TeV sky for transient followup and continuous source monitoring. Extending on previous work which compared the performance of different small IACT array configurations, the effect of implementing a stereoscopic trigger to these arrays has been studied. Only selecting events that simultaneously trigger multiple telescopes at once allows the trigger threshold to be reduced without increasing unwanted triggers from the night sky background. This lower trigger threshold can lead to more detected low-energy events, improving the observation of transient events which are typically far brighter at lower (GeV) energies. This talk will describe how the stereo trigger was fairly implemented, present the resulting changes in performance, and outline current research into implementing a topological trigger.

Likelihood-Free Inference applied to CTA

• Tristan Betterman (The University of Adelaide)

The TeV Diffuse Gamma-ray Emission: Time Variability and Prospects for Future Detection

• Peter Marinos (University of Adelaide)

We use the simulation software "GALPROP" to model the Milky Way's diffuse TeV gamma-ray emission and how the diffuse emission will vary over time. We compare GALPROP's predictions to observational data, investigating how the emission will impact the forthcoming CTA Observatory's Galactic plane survey.

Gamma-ray and Neutrino Emission from Supernova Remnants and Molecular Clouds

• Ryan Burley (The University of Adelaide)

High-energy gamma rays and neutrinos can be produced due to the hadronic interactions between protons escaping particle accelerators such as supernova remnants (SNRs) and nearby target material such as molecular clouds (MCs). By modelling the diffusion of protons escaping SNRs and interacting with nearby MCs in our Galaxy, we can predict the resulting gamma-ray and neutrino fluxes at Earth. Looking towards MCs as production sites for neutrinos may help identify Galactic neutrino sources, as previous searches primarily look at the sites of cosmic-ray accelerators. Observing either the gamma rays or neutrinos at large energies can also point towards Galactic PeVatrons. In this contribution, we will introduce a 3D modelling to calculate the gamma-ray and neutrino fluxes expected from hadronic interactions between all possible combinations of SNRs and MCs in our Galaxy. We will present a list of SNR and MC combinations that, under the right conditions, could produce a gammaray flux above 100TeV observable by the Cherenkov Telescope Array (CTA). These combinations also produce neutrino fluxes that may be observable by future neutrino detectors such as IceCube-Gen2 and KM3NeT.

Modelling the transport of electrons towards HESS J1825-137

• Tiffany Collins (The University of Adelaide)

HESS J1825-137 is one of the most powerful and luminous TeV gamma-ray pulsar wind nebulae (PWN). This makes HESS J1825-137 an excellent laboratory to study particle transportation in and around the powering pulsar. We have modelled the diffusive and advective transport of electrons from the powering pulsar, PSR 1826-1334. The resulting X-ray and gamma-ray emission was predicted through interactions with a 3D grid of interstellar medium gas (ISM), soft photon fields and a spatially varying magnetic field. We have also investigated the gamma-ray contamination of nearby HESS J18226-130 by HESS J1825-137

Update on CTA Dark Matter Reach

• Csaba Balazs (School of Physics and Astronomy, Monash University)

In our Bayesian WIMP detection project, we're refining our results published in 2112.10371.

A Compound Poisson Generator approach to Point-Source Inference in Astrophysics

• Gabriel Collin (The University of Adelaide)

I will present a new statistical approach to the problem of inferring the properties of point-source populations. This method will be shown to be superior to existing methods in the context of X-ray astronomy.

Millisecond pulsars in the globular cluster Omega Centauri

• Shi Dai (Western Sydney University)

The globular cluster Omega Centauri is the most massive and luminous cluster in the Galaxy. The gamma-ray source FL8Y 1326.7-4729 is coincident with the core of the cluster, leading to speculation that hitherto unknown radio pulsars or annihilating dark matter may be present in the cluster core. We discovered five millisecond pulsars (MSPs) in Omega Centauri and have been monitoring these pulsars with the Parkes telescope. We show that all five pulsars are located within the core region of the cluster and four of them are associated with X-ray sources. While no gamma-ray pulsation has been detected, their association with X-ray sources strongly suggests that MSPs in the core of Omega Centauri contribute a significant fraction of the detected gamma-ray emission.

The peculiar gamma-ray phenomenology of Terzan 5

• Roland Crocker (Research School of Astronomy and Astrophysics, Australian National University)

Terzan 5 has the largest population of millisecond pulsars of any globular cluster in the Galaxy. It is also unique in having an associated TeV source. The centroid of the TeV source, however, is measurably displaced away from the cluster. I will discuss a scenario motivated by cosmic ray transport physics than explains this peculiar displacement.

Short Update on Nova Detection Prospects

• Ashley Ruiter (University of New South Wales Canberra)

A brief update on the status of very high energy gamma ray detection from novae with the CTA will be given.

ORCs and Other New Wonders of Radio Surveys

• Miroslav Filipovic (Western Sydney University)

This is an exciting time for the discovery of SNRs in our and other nearby galaxies. I will report the discovery of J0624-6948, a low-surface brightness radio ring, lying between the Galactic Plane and the Large Magellanic Cloud (LMC). It was first detected at 888 MHz with the Australian Square Kilometre Array Pathfinder (ASKAP), and with a diameter of ~196 arcsec. This source has phenomenological similarities to odd radio circles (ORCs). Significant differences to the known ORCs - a flatter radio spectral index, the lack of a prominent central galaxy as a possible host, and a larger apparent size - suggest that J0624-6948 may be a different type of object. We argue that the most plausible explanation for J0624-6948 is an intergalactic supernova remnant due to a star that resided in the LMC outskirts that had undergone a single-degenerate type Ia supernova, and we are seeing its remnant expand into a rarefied, intergalactic environment.

Potoroo PWN

• Sanja Lazarevic (Western Sydney University)

Pulsars lose rotational energy through a wind of ultrarelativistic particles, and the synchrotron emission that arises will be observable in the form of a pulsar wind nebula (PWN). For a pulsar moving supersonically through the ambient medium, the PWN is characterised by a bow-shock shape around the pulsar and cometary tail. Currently, there are approximately 30 objects of this type, and Potoroo is one of them. I report on the recent discovery of Potoroo and its radio and X-ray properties.

Updates from University of Adelaide Students

• Sabrina Einecke (The University of Adelaide, Australia)
• Gavin Rowell (School of Physical Sciences, University of Adelaide)