Main Colloquium
Prof. Franco Vazza	SCHEDULED

University of Bologna, Italy

The origin of magnetic fields measured out to several Megaparsec from the centre of clusters of galaxies is not obvious, and can either be ascribed to primordial, or astrophysical processes (or a combination of both). I will review the most updated results on the observational quests to detect magnetic fields on very large scales with radio telescopes, and show how the combination with modern cosmological simulations can suggest a plausible answer to the puzzle. I will also discuss the upcoming science which might become possible thanks to the advent of the Square Kilometre Array, and in combination with other powerful observational probes.

	Special Colloquium
Vincent Eberle	SCHEDULED

Max-Planck-Institut für Astrophysik, Garching

TBD

	Special Colloquium
Dr Paul F. Goldsmith	SCHEDULED

Jet Propulsion Laboratory, California Institute of Technology

TBD

	Special Colloquium
Dr. Parthraj Bambhaniya	SCHEDULED

Institute of Astronomy, Geophysics and Atmospheric Sciences, Univ. São Paulo, Brazil

Recent observations by the Event Horizon Telescope and GRAVITY collaborations of Sagittarius A* at the centre of our Galaxy have generated significant interest in understanding the nature of the central compact object through shadow imaging, accretion dynamics, and precision measurements of S-star orbits. The classical Oppenheimer-Snyder-Dutt model predicts black hole formation through gravitational collapse, while Penrose’s cosmic censorship conjecture (CCC) suggests that the resulting singularity must remain hidden within an event horizon. However, the CCC remains unproven, and more recent gravitational collapse models open the possibility of horizonless supermassive compact objects. In this talk, I will discuss generalized shadow formation conditions for supermassive compact objects and how precise astrometric observations from the GRAVITY and UCLA Galactic Center groups can provide insights into the spacetime geometry near Sgr A*. I will also briefly present some of our recent work on General Relativistic Magnetohydrodynamics (GRMHD) simulations of relativistic accretion flows and magnetized plasma dynamics around compact objects, highlighting their importance for interpreting horizon-scale observations and black hole environments. Finally, I will discuss possible observational tests that may help distinguish black holes from alternative compact objects at the centers of galaxies. Keywords: Black Holes, Compact Objects, Shadows, Accretion Disks, Relativistic Orbits.

	Special Colloquium
Dr. Frederic Jaron	SCHEDULED

TU Vienna

The geodetic and astrometric application of VLBI is a powerful technique for the realization of global reference frames and the measurement of Earth orientation parameters. Source structure is one of the remaining unmodeled errors that prevent the technique from reaching its ultimate accuracy goals. We have developed a method to remove the influence of source structure from the output of the DiFX software correlator that fits into the common geodetic processing pipeline. In this talk I will present our approach and its application to observational data of the VLBI Global Observing System (VGOS). Improvement of closure group delays and post-fit residuals is obtained for selected sources when reliable image information is available.

	Main Colloquium
Dr. Jaroslav Haas	SCHEDULED

Charles University, Prague

TBD

	Special Colloquium
Dr. Christian Fendt	SCHEDULED

MPIA Heidelberg

TBD

	Special Colloquium
Prof. Shrinivas Kulkarni	SCHEDULED

California Institute of Technology, Pasadena, USA

TBD

	Main Colloquium
Professor Ziggy Pleunis	SCHEDULED

University of Amsterdam

TBD

	Main Colloquium
Prof. John McKean	SCHEDULED

Kapteyn Astronomical Institute, University of Groningen & ASTRON, Dwingeloo, The Netherlands

Gravitational lensing provides a powerful probe of the global mass properties of galaxies, which are best tested using observations at extremely high angular resolution. In addition, through detailed observations of the lensed images, it is possible to place tight constraints on the nature of dark matter through measuring the abundance and properties of low mass haloes via their subtle gravitational lensing signal. Here, we first present new observations with the VLA and HSA to better understand the source of so-called flux-ratio anomalies in four image gravitational lenses, which historically provided the first constraints on CDM using lensing studies. Next, we will present the analysis of the mass properties of ten massive elliptical galaxies at intermediate redshifts, by combining gravitational lensing and the sensitivity and resolving power of the Atacama Large Millimetre Array (ALMA) and global Very Long Baseline Interferometry (radio VLBI). Using imaging at 25 to a few milli-arcsecond resolution, we find that complex mass models with angular structure are strongly favoured by the data. In addition, such observations are sensitive to small-scale structure either in the lens or along the line-of-sight to the background source. From such an analysis of the data from global VLBI observations, we detect of a low mass (million solar mass) dark object, whose properties are inconsistent with a dark matter halo from either cold or warm dark matter models, but may be in agreement with more exotic models, like self-interacting dark matter. Finally, we present a brief overview of future studies using the SKA and a likely African VLBI facility that includes the SKAMPI, MPG-DZA and AMT dishes. Throughout we will also provide some asides on the pc-scale structure of radio jets, constraints on galactic-scale magnetic fields and electron densities, and the super-resolved (about 10 to 20 pc-scale) properties of starburst galaxies at redshifts 1 to 4.

	Main Colloquium
Dr. T. Joseph W. Lazio	SCHEDULED

University of Michigan

SunRISE is a constellation of six identical small spacecraft (6U CubeSats) that will form a space-based VLBI array. Each spacecraft carries a decametric-hectometric (DH, 0.1 MHz to 25 MHz) receiving system paired with global navigation satellite system (GNSS) receivers. The Solar DH receivers will be used to record signals from Type II and Type III solar radio bursts while the GNSS receivers will time stamp the data and enable the determination of the spacecraft locations for subsequent ground-based cross-correlation. SunRISE will reveal aspects of how solar energetic particles (SEPs) are accelerated at coronal mass ejections (CMEs) by tracking Type II bursts and how SEPs are released into interplanetary space from the Type III bursts. The six spacecraft that form the SunRISE interferometer will fly in a passive formation in a supersynchronous geosynchronous Earth orbit (super-GEO). The nominal baseline will be 10 km, obtaining an angular resolution of approximately 10' at 10 MHz. I describe the implementation of SunRISE, illustrating how the combination of on-board and ground operations and processing are required to achieve a fully space-based VLBI array. While SunRISE is a NASA Mission of Opportunity that will conduct science in its own right, it also is intended to be a pathfinder for future space-based radio astronomy missions. I provide an initial assessment of the "experience gained" for future missions, from the perspective of both the SunRISE science and technical implementation.

	Main Colloquium
Dr. Casey Law	SCHEDULED

Caltech, USA

TBD

	Main Colloquium
Professor Ilse de Looze	SCHEDULED

Ghent University

TBD

	Main Colloquium
Prof. Dr. Felix Aharonian	SCHEDULED

DIAS/Dublin and MPIK/Heidelberg

PeVatrons - cosmic-ray factories capable of accelerating particles to petaelectronvolt (PeV) energies - are widely believed to play a key role in resolving the century-old mystery of the origin of Galactic cosmic rays. For decades, the nature of these objects has been the subject of extensive theoretical and observational studies, with supernova remnants long regarded as the prime candidates. In recent years, major observational advances, primarily the detection of gamma rays with energies exceeding 100 TeV from dozens of Galactic sources, have led to a breakthrough with far-reaching implications. Taken together, these developments suggest that the Milky Way hosts a diverse population of extreme particle accelerators capable of producing cosmic rays at PeV energies. At the same time, increasingly precise measurements of cosmic-ray spectra and composition have significantly improved our understanding of Galactic cosmic rays from GeV to PeV energies. These observations reveal that a diversity of cosmic-ray accelerators associated with several Galactic source populations, including supernova remnants, star-forming regions, pulsar wind nebulae, and microquasars, may create, despite their fundamentally different physical environments, near-ideal conditions for particle acceleration operating close to the theoretical limits. This review summarizes the theoretical predictions, observational discoveries, and current interpretations of PeVatrons, discusses their implications for high-energy astrophysics, particularly for the origin of Galactic cosmic rays, and outlines future directions for multiwavelength observations.

	Special Colloquium
Dr Minghui Xu	SCHEDULED

GFZ Potsdam

TBD