Netherlands Astronomy Conference 2026

5 min - SRON
5 min - KNA-RNAS
5 min - LOC

We present our ongoing development of radio astronomy instrumentation and the science drivers behind it. Two examples of our work include L‑FIRE (Low‑Frequency Interferometric Radio Explorer), a concept for a distributed radio telescope in low Earth orbit, and contributions to the DEX (Dark Ages Explorer) lunar radio telescope concept. We analyse how our targeted science cases shape the...

The discovery of gravitational waves has transformed astrophysics, enabling the study of the Universe in a fundamentally new way. The next major breakthrough is expected with the launch of the European Space Agency’s Laser Interferometer Space Antenna (LISA) in the mid-2030s. By opening the millihertz gravitational-wave window, LISA will access a rich population of astrophysical and...

Unintended electromagnetic radiation (UEMR) from large Low Earth Orbit satellite constellations poses a growing threat to radio astronomy. First identified with the Low Frequency Array (LOFAR), this weak but persistent emission from onboard electronics can be broadband and difficult to mitigate, yet is strong enough to contaminate sensitive observations.

Follow-up measurements with other...

The modeling of stars and stellar populations is a key element in our understanding of the Universe, and plays a large role in the scientific exploitation of observations as astronomy moves into the big data era. However, despite the identification of the key processes and fundamental equations that drive stellar evolution almost a century ago, and the broad availability of numerical methods...

We have just passed the 10th anniversary of the first-ever gravitational-wave detection. With more than 150 detections of merging binary black holes (and counting), gravitational-wave observations have entered the ‘population era’. The data already reveal a rich structure in the black hole mass function. However, for the first time, we have now obtained enough detections to begin identifying...

Images are among the most important tools astronomers use to understand the Universe. As machine learning techniques are increasingly used in astronomy, we explore what machines “see” in galaxy images, with a particular focus on galaxy morphology. 

Galaxy morphology provides one of the most direct observational signatures of evolutionary pathways, making its taxonomy a central pursuit in...

The Near-Ultraviolet eXplorer (NUX) is a proposed wide-field (~67 square degrees) ground-based observatory, designed to explore the shortest UV wavelengths (300 to 350 nm) observable from Earth's surface. NUX’s primary goal is to deepen our understanding of fast (hours to days) and hot transient phenomena, including shock-breakout emissions from supernovae and electromagnetic sources...

Jupiter’s famous banding reflects powerful jet streams that probe deep atmospheric and interior processes. Since arriving in 2016, NASA’s Juno spacecraft, in a series of close, polar perijove passes, has returned high-precision gravity measurements from its Gravity Science experiment (tracking Doppler shifts of the spacecraft), alongside complementary data from the Microwave Radiometer and...

To understand the origin of heavy elements, it is crucial to understand early star-forming activity. Observations with the James Webb Space Telescope have unveiled more early galaxies than expected, highlighting the need for complementary tracers of obscured star-formation in the early Universe.
(Sub)millimetre spectroscopy provides direct access to dust emission and far-infrared...

Several extragalactic Fast X-ray transients (FXTs), detected as bursts of soft X-ray photons with durations of hundreds of seconds by the Einstein Probe mission, have recently been linked to the collapse of a massive star. For those FXTs, the ensuing supernovae are similar to those associated with long gamma-ray bursts (long-GRBs). Under the fireball model for long-GRBs, the collapse of a...

Dust is a minor constituent of our Galaxy but dominates our view of it. To understand its key role in the lifecycle and energy balance of interstellar matter, we must understand its properties and processing.
X-ray spectroscopy provides a unique tool to study the properties of interstellar dust. The X-ray band contains absorption edges of important components of interstellar dust, such as C,...

In the last 15 years, the Atacama Large Millimeter/submillimeter Array
(ALMA) has revolutionized astrophysics by providing unprecedented
resolution and sensitivity for observing the cold Universe. However, in
another 15 years from now, the scientific landscape will have changed
dramatically as major new facilities come online, and ALMA itself will
approach its fourth decade of operation....

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TO BE EDITED

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous ingredients of the interstellar medium where they contain 15 to 20% of all the carbon and play a crucial role in the ionization balance and gas heating (Tielens et al., 2008). PAHs produce bright emission spectral features called the Aromatic Infrared Bands (AIBs), which are detected in great detail thanks to the exquisite spectral...

The missing baryons, that is, the yet-unobserved ordinary matter in the large-scale structures of the Universe, have been shown by simulations to reside mostly in filaments of the cosmic web. As this phase of the cosmic gas is becoming observable, currently in the outskirts of galaxy clusters and in short filaments, so-called bridges, it is becoming crucial to understand their detailed gas...

Merging galaxy clusters host Megaparsec-scale diffuse radio emission that traces re-accelerated cosmic ray electrons in the intracluster medium. Recent observations report a growing number of enigmatic radio filaments connected to the lobes of cluster radio galaxies, which may transport and preserve relativistic electrons and thereby seed diffuse cluster-scale radio sources. Resolving these...

We investigate a dust-driven vertical shear instability (DVSI) in a radially local, vertically stratified isothermal shearing box. Unlike the classical vertical shear instability, which relies on baroclinicity from global thermodynamic gradients (radial temperature gradients with finite cooling), DVSI is triggered by dust backreaction that generates axisymmetric vertical shear in an otherwise...

NICER has enabled mass–radius inferences for pulsars using pulse profile modeling (PPM), providing constraints on the equation of state (EOS) of cold, dense matter. To date, PPM and EOS inference have been carried out as two separate steps, with the former using EOS-agnostic priors. This approach has several drawbacks. Ideally, one would perform a fully hierarchical Bayesian inference where...

We present a morphological analysis of dwarf galaxies in the Perseus cluster using Euclid Early Release Observations (ERO), exploiting the VIS instrument's diffraction-limited resolution and exceptional surface brightness sensitivity. Working from the ~1100-dwarf ERO catalog of Marleau et al. (2025), we develop a novel cumulative light fraction approach for measuring isophotal shapes in low...

Since the launch of the X-ray satellite Einstein Probe (EP) in 2024, we have finally been able to constrain the origins of several fast X-ray transients (FXTs). Astrophysical transients are known across, and beyond, the whole electromagnetic spectrum, including gamma-ray bursts (GRBs) and gravitational waves. But for long our knowledge on the progenitors of FXTs remained poor. Now that we are...

Atmospheric boundary conditions play a critical role in interior modeling, as they define the interior adiabat and strongly influence the inferred planetary radius for a given interior structure. For hot Jupiters, their extended and highly irradiated atmospheres enable detailed observational constraints on atmospheric composition, now reaching unprecedented quality with JWST and ground-based...

Warps are responsible for various global disc phenomena and observational signatures and have mostly been studied using global hydrodynamical simulations. However, their role in planet formation and affecting dust instabilities is best studied in a local frame. I will present our recent efforts in modelling dusty warps in a local shearing box and show that warps can cause dust instabilities...

The discovery of the phase space spirals in the Solar neighborhood in Gaia Data Release 2 has prompted various attempts to understand their origin. A source of bending waves, which has been neglected as a cause of the phase spiral, is irregular gas inflow along the warp.
We aim to study whether perturbations by the gas warp could induce phase spirals. Accounting for this additional formation...

In the past decade, black holes evolved from a theoretical prediction by General Relativity to actually observable objects. In particular, accretion and outflow of plasma leave key signatures across the electromagnetic spectrum, from the Event Horizon Telescope radio observations to X- and γ-rays, from the shadow size to the shape of the spectral energy distribution (SED). These signatures...

We present the development of a resistive-MHD (RMHD) module within the ideal-GRMHD code GRaM-X. GRaM-X (General Relativistic accelerated Magnetohydrodynamics on AMReX) is a new, GPU-accelerated, dynamical-spacetime ideal-GRMHD code that extends the capabilities of the Einstein Toolkit to GPU-based exascale platforms. It features three-dimensional adaptive mesh refinement (AMR) on GPUs through...

The extended hot ($T=10^6$ K) gas phase of the circumgalactic medium (CGM) is an essential component for studying the baryon cycle of late-type galaxies, because it could supply the galaxy with gas to sustain star formation and possibly contains many of the 'missing' baryons.
Using a simple semi-analytic model based on hydrostatic equilibrium and the latest eROSITA observations, we evolve the...

The Class I protostellar stage is a critical phase early in stellar evolution, where a rotating disk of gas and dust is formed, setting the chemical budget for the formation of planets. However, unlike the slightly older Class II disks, Class I protostars are deeply embedded in their natal envelopes. With the coverage, sensitivity and spectral resolution of the JWST, we are now capable of...

In the interstellar medium, multiple processes in star formation and
evolution deposit, clear, and reorganize dust molecules around stellar
populations. In the Physics at High Angular Resolution in Nearby
Galaxies (PHANGS) surveys, stellar associations trace loosely bound
young stars in recent star formation sites. Leveraging the synergy
between HST and JWST, we measure dust extinction of...

Ultraluminous X-ray sources (ULXs) can be considered for the most part an extreme version of X-ray binaries accreting at super-Eddington accretion rates. The most extreme manifestation of this process, other than their abnormally bright X-ray luminosities ($L_\mathrm{X} \gtrsim 10^{39}$ erg/s) occurs in the form of hundred-parsec nebulae of ionized gas surrounding them, offering a nearby...

Massive stars are fundamental drivers of cosmic evolution, shaping the interstellar medium, enriching galaxies with heavy elements, and producing compact remnants. A large fraction reside in binary or higher-order multiple systems, with most undergoing interaction during their lifetimes, profoundly altering their evolution and final outcomes. Understanding the physics of binary interaction is...

Intro: Katie Mulrey (2 minutes)

Keynote speaker: Marion Mulder (30 minutes)

Title: “Beyond AI - Equity & inclusion in the current political situation”
Abstract: When looking at equity & inclusion in the current (political) situation, AI is one topic that clearly comes to mind. Marion Mulder has been speaking about inclusion through a technology lens for many years and will guide us...

Most of the visible matter in the universe exists as highly ionized plasmas, consisting of highly charged ions (HCIs). Due to their high effective nuclear charge, HCIs strongly emit radiation in the X-ray regime and can be observed with X-ray satellites, such as XRISM.
To study these ions in a laboratory setting and establish spectral benchmarks that meet the accuracy requirements of XRISM...

The Cherenkov Telescope Array Observatory (CTAO) will be the next-generation ground-based facility for very-high-energy gamma-ray astronomy. In contrast to space-based instruments, ground-based gamma-ray observatories detect the brief flashes of Cherenkov light produced when high-energy gamma rays interact with the Earth’s atmosphere, generating particle cascades. This technique enables the...

This will be a talk in two parts.

In the first part I will given an overview of the European Southern Observatory, its capabilities (VLT, ALMA, VLTI, La Sila) and current developments, including the construction of the Extremely Large Telescope where The Netherlands plays an important role, among others through the METIS, Micado and MOSAIC instruments.

In the second part I will give an...

Current high-contrast imaging instruments are limited by wavefront errors originating from non-common path aberrations due, for example, to manufacturing errors in the optics and temperature drifts in the system. These create quasi-static speckles in the final science image that are difficult to distinguish from companions. The Self-Coherent Camera (SCC) exploits the light incoherence between...

NOVA’s instrumentation program is driven by scientific ambition: the need for access to specific data shapes our participation in major international projects. With a strong focus on ESO facilities, NOVA aims both to contribute to future instruments and to sustain and develop key technical expertise within its instrumentation groups.

As ESO prepares for the post-2030 landscape through the...

After more than 30 years of talking, the construction of the Square Kilometre Array (SKA) is now well underway. In this talk, I will give a update on construction, science verification, and what this stage of project development means for the Dutch astronomy community. In particular, I will focus on the establishment of our own regional centre, and its expected role in the community. NAC is...

iDaVIE (immersive Data Visualisation Interactive Explorer) is a software tool developed at IDIA (Institute for Data Intensive Astronomy) in Cape Town (https://idavie.readthedocs.io/en/v1.1/). It allows viewing, manipulation and analysis of 3D data in a Virtual Reality setting where one is immersed in the 3D data environment.

There are two versions of iDaVIE. iDAVIE-v allows viewing of 3D...

In a 2021 study on Dutch traditional media, “plasma physics” was found to be the lowest represented topic amongst news articles discussing physics, at only 0.4%[1]. In contrast, “astronomy and astrophysics” (a topic overlapping with plasma) had over 100 times more representation with 44.4%. Poor science communication representation has led the general public to be unaware of technological...

The three mobile planetariums operated by the Netherlands Research School for Astronomy (NOVA) are a highly effective and successful way of introducing astronomy to school students in a live and interactive way. Our mission is to let every school kid experience the thrill of discovery once in their school career. Since the start of the project, it has reached over 600,000 children. However,...

The outflows of massive stars significantly affect their stellar evolution and surroundings. The mass-loss rates of these stars is thus essential to constrain from their stellar spectra. However, this requires the detailed spectroscopic analysis of large samples of stars. Precisely modelling the wind and atmospheres of massive stars is computationally very expensive, which severely limits the...

The Dutch astronomy community is internationally recognized for its scientific excellence and strong collaboration across institutes. Sustaining this strength requires continued coordination, visibility, and accessible channels for collaboration.

In this presentation, I will briefly introduce my relatively new role as NOVA’s Research and Community Coordinator and outline ongoing efforts to...

We present a new method for fast inference of pulsar emission and interstellar medium (ISM) parameters directly from frequency-resolved pulse profiles. Accurate parameter estimation is challenging due to strong degeneracies, and classical Bayesian likelihood-based fitting becomes computationally expensive for high-dimensional parameter spaces.

We build a physically motivated simulator that...

With the boom of applications of deep neural networks in (astronomical) research, we have grown an urgent need to crack open our own black boxes, lest our reviewers start asking us difficult questions we cannot answer. Enter the field of "explainable AI" (XAI), in which methods to solve this issue are developed and studied. I will give a short introduction into XAI in general, and present our...

Over the past few decades, social media has fundamentally transformed the global communication landscape. Videos have become an increasingly important form of communication, from short-form to long-form content on platforms like YouTube. Especially for smaller institutions and outreach offices, this requires a systematic adaptation of their communication approach. The central resource of the...

We investigate the impact of stellar cluster initial conditions on the dynamical evolution of planetary systems. Two configurations are considered; a sub-virial fractal distribution and a virialised Plummer distribution. Both models are initialised with a virial radius of $0.5$pc, $150$ stars and $~145$ planetary systems. Five realisations of each configuration are performed with identical...

Cassiopeia A (Cas A), the youngest known core-collapse supernova remnant (SNR) in the Milky Way, offers an unparalleled view of the explosions of massive stars. A >350 ks observation with XRISM has delivered an unprecedented high–spectral-resolution X-ray view of this archetypal remnant and produced the mission’s most productive dataset to date, with 5+ published papers. In this talk, I will...

To understand how galaxies form and evolve, we must first contend with dust. Though it makes up only a tiny fraction of a galaxy's mass, interstellar dust acts as a cosmic veil, absorbing starlight and re-emitting it at longer wavelengths. This process, known as attenuation, significantly alters the spectra we observe with instruments like JWST. Until now, large-volume cosmological simulations...

The sizes of galactic disks are known to depend on stellar mass and redshift, with galaxies of a given mass expected to be more compact at higher redshifts. However, observational studies have uncovered disk galaxies at z~3 that have sizes significantly larger than expected from the mass-size relation. Notably, these ‘giant disks’ are preferentially found in proto-clusters, suggesting that...

YSES 1 b is a directly imaged young substellar companion on a wide orbit of 160 AU, making it an interesting challenge for formation theories. Initial photometric observations with SPHERE and NACO from Y to M band suggested physical parameters of Teff=1700 K, R=3 R_J and M=14 M_J. Here, we present new observations in the r’, i’ and z’ band using the MagAO-X instrument and revisit the modelling...

The Square Kilometre Array (SKA) is a next-generation radio telescope currently under construction in South Africa and Australia.
Its low-frequency part (50-350 MHz), located in Australia, features nearly 60,000 antennas in a core region of about 1 km diameter.
The unprecedented antenna density allows to observe individual cosmic-ray air showers to a level of detail no other observatory can...

In order to understand star-forming processes in dusty star-forming galaxies, observations of dense gas tracers, such as HCN, HCO+ and HNC, are required to link existing studies of their molecular gas, typically traced via CO or [CII], and obscured star formation, traced via the dust continuum. Previous studies suggest that high-z DSFGs could be surprisingly lacking in dense gas for sources...

Fast radio bursts (FRBs) are millisecond-duration, extragalactic radio transients of unknown origin. The FRB backend on the CHIME telescope (CHIME/FRB) is the most prolific FRB discovery machine, having detected more than 4000 unique sources of FRBs. The recent addition of three CHIME Outrigger stations across Northern America enables the precise sub-arcsecond localization of multiple FRBs per...

The interpretation of exoplanet spectra obtained with JWST typically assumes that observed atmospheres are in steady state. In this work, we challenge that assumption by demonstrating that stellar flares can induce rapid and long-lasting changes in atmospheric composition that directly impact observables. We model the effects of recurrent stellar flaring on metal-rich exoplanet atmospheres...

Energetic particle events occur when charged particles are accelerated to near-relativistic energies during stellar flares or coronal mass ejections, and they help shape planetary atmospheres through erosion and chemistry. Traditional stellar activity probes, such as optical and soft X-ray flares, trace thermal plasma and are effectively blind to escaping relativistic particle beams. Based on...

Galaxy mergers represent a critical and complex phase in galaxy evolution, often triggering nuclear activity and intense episodes of central star formation that can profoundly influence the subsequent evolution of the system. In this talk, I present new insights into the impact of active galactic nucleus (AGN) feedback on the multi-phase interstellar medium (ISM) in the central region...

The future of very low frequency radio astronomy lies on the Moon, where the absence of an ionosphere and terrestrial radio interference enables observations below ~30 MHz. The upcoming LuSEE-Night mission will deploy four monopole antennas on the lunar farside to measure the global signal from the Epoch of Reionization and coherent emission from exoplanets. Before scientific measurements are...

Active galactic nuclei (AGNs) influence their host galaxies through powerful winds that drive large-scale outflows, regulating star formation by heating, removing, or compressing the interstellar medium (ISM). Despite their importance for galaxy–supermassive black hole co-evolution, the impact of AGN-driven feedback on the surrounding molecular gas reservoir remains poorly understood. In this...

H$\alpha$ emission is abundant in ultracool dwarfs (UCD), but its origin is unclear. While it may stem from residual star-like, chromospheric emission, it may also be attributed to planet-like magnetospheric emission akin to Jupiter's aurora. A way to resolve this issue is to measure the spatial distribution of H$\alpha$ emission on the UCD. Chromospheric emission would appear distributed in...

4U 1556-60 is an X-ray binary that was discovered more than 50 years ago as a persistent X-ray source. However, very little was known about it, including fundamental properties such as its distance, whether the accreting compact object was a black hole or neutron star, and its orbital period. Recently, Gaia Data Release 3 has provided a parallax for the optical counterpart of 4U 1556-60,...

We present the discovery of an extraordinary overdensity around a source of the ALMA Large Program REBELS at z=7.35, among the most extreme proto-clusters known beyond z>7. Within just 21″×21″ (Δz<0.01), we identify 5 sources in [OIII]5007 with NIRCam/Grism observations, also showing in ALMA data as 4 of the brightest [CII] 158μm emission known at z>7. The properties of these galaxies show...

GRS 1915+105, the low mass X-ray binary with the largest accretion disk and the first microquasar observed with superluminal jets, has stayed in a high-luminosity outburst for decades since its discovery in 1992. However, in mid 2018, the source entered a new phase in which the X-rays suddenly dropped to an unprecedentedly low flux that was quickly followed by a rebrightening in the radio,...

We present the first large-scale statistical analysis of an extensive catalogue of interplanetary Type III solar radio bursts compiled through human participation. The catalogue is based on Radio and Plasma Waves (RPW) observations from Solar Orbiter, collected through the citizen-science campaign Solar Radio Burst Tracker hosted on Zooniverse, with contributions from 867 volunteers between...

On August 31st, 2024, the LOFAR radio telescope paused after 15 years of operations to undergo a major upgrade. In this upgrade, our lessons learned from that period are incorporated into new hardware, firmware, and software. Except for the antennas, almost everything is being replaced as we build LOFAR2.0: receiver units, digital beam formers, clock distribution, network infrastructure, the...

The mechanics of binary evolution remain largely invisible other than the luminosities that reach us. However, these luminosities are the end result of a chain of interdependent feedback processes spanning the entire binary system to accrete material from a still-evolving donor star. With recent developments a clear picture of this mass transfer is now possible. Only by tackling system...

The large-scale structure of the Universe encodes a wealth of information about cosmology and galaxy formation. For decades, two-point correlation functions have served as a cornerstone of this effort, distilling the complex distribution of matter into powerful statistical measures. These summary statistics underpin precision constraints on the standard cosmological model and provide key...

Water (H$_2$O) is key for habitability, but the delivery mechanism to (forming) planets is not yet well understood. The James Webb Space Telescope, especially through the MIRI instrument, can now study the planet-forming regions (inner few au) of disks around young stars. Hundreds of ro-vibrational (<10 $\mathrm{\mu}$m) and pure rotational (>10 $\mathrm{\mu}$m) transitions can probe the...

Fast radio bursts (FRBs) are among the most mysterious and exciting phenomena in modern astrophysics. These are extremely energetic bursts originating from extragalactic distances, providing unique probes of the intergalactic medium and offering new ways to study the universe at cosmological scales. Despite major progress in recent years, many questions remain open about their origins,...

Fast Radio Bursts (FRBs) are rapidly becoming unparalleled cosmological tools: the dispersion of these millisecond-duration bursts traces the ionised material along the line of sight, while scattering and Faraday rotation encode the turbulence and magnetic field of intervening media. Nowadays, with more than a hundred FRBs localised to their host galaxies at increasing redshifts, they offer a...

Current and planned X-ray telescopes have imaging resolutions on the order of arcseconds or worse, which exceeds the theoretical diffraction limit by four orders of magnitude. By leveraging a compact, single-spacecraft design, X-ray Interferometry (XRI) can achieve an EHT-like spatial resolution of tens of microarcseconds.
This enormous leap in resolution allows for direct imaging of...

Long-period transients (LPTs) were discovered a few years ago as mysterious radio sources that produce bright pulses that repeat on periods of minutes to hours. While they have been suggested to be extremely slow magnetars or white dwarf binaries, conclusively determining their origins has been complicated by their large distances and high extinction, which make follow-up at other wavelengths...

Understanding the Epoch of Reionisation remains one of the pivotal tasks for modern cosmology, and next-generation telescopes such as EUCLID and JWST are opening up the path to the first precision constraints on reionisation derived from the Lyman-alpha damping wing signature imprinted by the foreground neutral intergalactic medium (IGM) on the spectra of high-redshift quasars.

We developed...

Detection of auroral radio emission from exoplanets presents a unique opportunity to directly probe their magnetic fields. By studying the magnetic characteristics of exoplanets, we can better-understand their atmospheric retention, long-term evolution, and ultimately their habitability. However, an unambiguous detection remains elusive, largely due to limited sensitivity at low radio...

Accreting stellar-mass black holes in Black Hole X-ray Binaries (BHXRBs) are known to undergo distinct accretion states, likely corresponding to changes in the structure of the inner accretion flow and accompanied by strong variations in spectral energy distribution, jet production, and variability properties. These accretion states evolve during outburst cycles, with relativistic jets...

We present a high-resolution spectroscopic study of the ultracompact neutron-star LMXB 4U 1916–053 (Porb ≈ 50 min), a prototypical dipping system in which recurrent intensity drops are produced by variable absorption in disk-associated plasma. Using new XRISM/Resolve observations together with simultaneous XMM-Newton data, we investigate the structure, ionization state, and kinematics of the...

Pebble accretion is widely considered a key, and probably necessary, ingredient for rapid planet formation. However, most studies still rely on simplified gas prescriptions or assume a single particle size. In this work, we revisit pebble accretion using a multifluid hydrodynamical model that evolves the gas and multiple pebble species self-consistently. This allows us to move beyond static...

In this talk, I will present a real-time transient detection pipeline in the image plane for LOFAR data. This pipeline creates short duration snapshot images (seconds to a minute) and searches for transient sources in the differences between consecutive images. Upon detection of a transient candidate that passes our filters, buffered LOFAR station data will be dumped for offline analysis....

Local scaling relations of disc galaxies contain key information on the different physical processes that regulate their formation and evolution. While these relations are well established at z=0, their physical origin and evolution across cosmic time remain poorly constrained.

We present a new and unique radially resolved semi-analytic model for the evolution of star-forming disc galaxies,...

Recently, a new population of bright, seconds to minutes duration radio transients have been discovered, for example the long period transient discovered by de Ruiter et al. (2024). Our team developed a fast subtraction imaging pipeline to search for more of these transients in data from the LOw-Frequency ARray (LOFAR). LOFAR is undergoing a major upgrade to LOFAR2.0, which includes a new,...

We know that different astrophysical objects can accelerate charged particles to extremely high energies, but, we don’t exactly know what these sources are or how they do it. At high energies, we study cosmic rays via the air showers they generate when they interact in the Earth’s atmosphere. These air showers emit sharp pulses of radio emission that contain information about the development...

Astrophysical jets are observed from young stellar objects to accreting compact objects, yet their formation and collimation remain poorly understood. In particular, the role of radiative cooling in driving flow convergence and promoting jet formation remains uncertain. Laboratory plasma experiments provide a complementary approach by enabling controlled studies of supersonic, radiatively...

The BlackGEM telescope array has been in regular operation for over a year now. It has been actively following up on gravitational wave alerts from LIGO-Virgo-KAGRA, as well as high-energy alerts from SWIFT and other telescopes. Additionally, BlackGEM has been utilized for the Local Transient Survey to regularly monitor the nearby universe, and it has conducted deep observations of the...

High-energy neutrinos act as cosmic messengers, pointing back towards sources in the
universe. These particles have an extremely low flux, so radio techniques can help us to
probe large volumes and thus increase detection rates. The Radar Echo Telescope (RET)
aims to detect neutrinos by reflecting radio signals from the ionized trail left behind by
the cascade. This is done in ice, as it...

Fast X-ray transients (FXTs) are singular bright bursts of X-rays. The Einstein Probe (EP) satellite, launched in 2024, is revolutionising the field thanks to its timely discoveries and precise localizations of the events. These newly discovered FXTs have a strong connection with gamma-ray bursts (GRBs), which comes from the emission of a relativistic jet pointing towards us.
It seems that...

The Ionised interstellar medium (IISM) is a major source of unmodelled noise in Pulsar Timing Array (PTA) data. Spatial effects like scattering and scintillation lead to short-term diffractive and long-term refractive noise. These overlaid with variations in electron density further complicate and bias PTA noise models - directly impacting sensitivity to low-frequency gravitational waves....

Since the development of the LOw Frequency ARray (LOFAR), it has played an important role in the search for variable sources at low radio frequencies. In recent years, numerous types of transient radio pulsations have been identified, including variable x-ray binaries and giant pulses from pulsars. To systematically search for these sources, an automated pipeline TraP was developed. This...

Sgr A* displays intermittent IR and X-ray flaring, possibly due to regions of magnetic reconnection near the event horizon. While this mechanism is favored by both phenomenological modeling and simulations, such methods rely on simplified expressions of the radiating electrons’ energy distribution to model the resulting multiwavelength emission. Rather than this approach, we introduce a new...

We rarely have images of individual stars before they end their lives as supernovae. This makes the study of supernova, or more generally astrophysical transient environments invaluable for constraining their stellar progenitors. Much effort has been invested in studying the large populations of low redshift supernovae that have been uncovered in recent years, along with populations of...

We present spectral mapping observations of DESHIMA 2.0 at the 10-meter ASTE telescope in Chile, obtained as part of its commissioning and science verification (CSV) campaign during 2024. DESHIMA 2.0 is an on-chip spectrometer operating between 200-400 GHz with a moderate filterbank resolution of R ~ 500, which is achieved using a superconducting filterbank coupled to an array of microwave...

Sulphur is one of six essential elements to create life as we know it. Tracing the chemical pathways of sulfur-containing molecules that could be present in molecular clouds and planetary atmospheres is important to understand the delivery of sulfur to forming planetary systems. Among possible sulfur reservoirs, sulphur allotropes are potential candidates. Octasulfur is the most stable sulfur...

Before the Gaia mission, eccentricity in wide, evolved binaries (with periods of ~10²–10⁴ days) was considered an oddity, as only a few small samples were known. Recent observations, however, reveal that eccentricity is widespread in these systems, with both the range and the maximum values of observed eccentricities increasing with orbital period. This pattern—consistent across diverse...

Gas-giant exoplanets are expected to generate low-frequency radio emission (< 40 MHz) via the cyclotron maser mechanism. Detecting this emission is likely the only viable way to measure exoplanets’ magnetic field and space-weather conditions. Despite many attempts, there has not been a confirmed detection of an exoplanet in the radio band. I will present results from our ongoing search for...

In gravitational-wave astrophysics, the chirp mass is one of the two primary quantities directly inferred from detected signals. This combination of component masses exhibits a non-uniform distribution with distinct features, most notably a peak around 30 solar masses whose origin remains heavily debated. Reconstructing the systems contributing to this peak provides surprising results: nearly...

The energy region around the "knee" of the cosmic-ray spectrum marks a transition where changes in the observed spectral shape and composition indicate a shift in the underlying physical processes of the sources of Galactic cosmic rays. In this work, cosmic-ray transport around this energy is simulated with CRPropa, using the JF12 Galactic magnetic field model with both large-scale and...

The GUSTO mission aims to unravel the life cycle of interstellar gas in the Milky Way and Large Magellanic Cloud (LMC), tracing the formation and destruction of star-forming clouds, probing the dynamics of the Galactic Center, and exploring the interplay between star formation, stellar feedback, and the structure of the interstellar medium. By mapping [CII] and [NII] emission, GUSTO provides...

The super-fast (~day), very-high-energy (VHE; >0.1 TeV) photon flares from the nearby active galactic nucleus M87 provide a unique, exciting opportunity to fast-forward our understanding of particle acceleration in jets. After a long break since 2010, the Event Horizon Telescope (EHT) multiwavelength (MWL) campaign captured a new VHE flare in 2018 with unprecedented frequency coverage...

Thermonuclear X-ray bursts are observed from weakly magnetized neutron stars in low-mass X-ray binaries (LMXBs). In these systems, accreted material such as hydrogen and/or helium from a donor star undergoes unstable thermonuclear burning on the NS’s surface. These bursts typically show a fast rise for a few seconds, followed by an exponential decay for tens of seconds. Thermonuclear bursts...

Millisecond pulsars are among the most precise clocks in the Universe. The triple system PSR J0337+1715, composed of a neutron star and two white dwarfs, is a unique gravitational laboratory, that enables excellent tests of the Strong Equivalence Principle (SEP). With microsecond-level timing precision, even tiny deviations from theoretical models become detectable. However, recent analyses...

Direct cosmic-ray measurements determine the spectra and composition of charged particles and show that the Galactic spectrum steepens around $\sim 3$ PeV, the so-called knee. This feature is widely taken to mark the energy where typical Galactic accelerators or Galactic confinement begin to fail, but the responsible source class is still unknown. Supernova remnants are the standard...

The molecular composition of exoplanetary atmospheres can be heavily influenced by non-equilibrium and photochemistry. Determining this composition can thus be very computationally demanding, with conventional ODE-solving strategies often taking hours to converge. This makes incorporation into retrieval algorithms difficult. As such, we investigate the application of machine learning for...

The physical state of a star is primarily determined by its initial mass and chemical composition, while other factors (e.g. rotation, magnetic fields, companion) play a secondary role. Precise stellar masses are therefore fundamental for constraining stellar structure and evolution (SSE), particularly for rapidly evolving stars more massive than ~1.2 solar masses (i.e. OBAF-type stars)....

Massive star formation is thought to occur within the Galactic disk, so the presence of massive stars at a Galactic height of more than a kiloparsec is unexpected given their short lifetime. Using the Alma Luminous Star (ALS) III catalogue (Pantaleoni González et al. 2025) and Gaia DR3 data, we determined the scale height of Galactic OB candidate stars (64±4 pc) and identified 90 luminous...

High PeV to EeV cosmic rays can be used to probe extreme environments in the universe like supernovae and AGN. When these cosmic rays hit the Earth's atmosphere they generate large cascades of secondary particles called "airshowers". The evolution of these airshowers is still not completely understood, with current efforts to resolve it focusing on beamforming with radio arrays like LOFAR....

The discovery of gravitational waves (GWs) has revolutionized our understanding of the Universe, providing a unique observational window into cosmic phenomena. Active Galactic Nuclei (AGN) are promising sites for the formation of binary black holes (BHs).
In this scenario, the so-called AGN channel, BHs from the galactic nucleus gradually align with the AGN accretion disk, forming a dynamic...

Post-red giant branch (post-RGB) and post-asymptotic giant branch (post-AGB) binaries consist of a primary star that has recently evolved off either the RGB or AGB, having lost the majority of its envelope, and a main-sequence companion. These systems are characterised by the presence of a stable circumbinary disc. Observed Galactic post-AGB and post-RGB binaries exhibit eccentricities between...

Type-I X-ray bursts in neutron star (NS) low mass X-ray binaries are highly energetic events with the power to dynamically change the accretion flow. Studying such dynamical effects is a powerful new method that could shed light on accretion disk physics, coronae and the origin of relativistic jets. Correctly modelling time resolved X-ray spectra during these bursts allows for measurements of...

State-of-the-art numerical simulations of the early stages of planet formation are often limited by computational cost due to the complexity of the included physics. Multi-physics 3D simulations of the dynamics of gas coupled with dust grains of multiple sizes including collisional evolution has long been unfeasible using conventional methods. We propose the use of machine learning,...

The mechanism of angular momentum transport in a neutron star boundary layer (BL) is still a major open problem in accretion disc theory. As well as the cooling curve after a type 1 thermonuclear burst, which requires some unexplained shallow heating source to explain its relaxation time. In this work, we show that acoustic waves generated in the BL due to the supersonic shear are both...

P-nuclei are neutron‑deficient isotopes whose long‑sought‑after origin in the chemical enrichment of the Universe remains unknown. They are predicted to be produced on accreting neutron stars in X-ray binaries (XRBs), during stable burning and in thermonuclear (type I) X-ray bursts. Until now, it is not expected that these nuclei can leave the gravitational well of the neutron star. However,...

We use the TNG300-1-Dark simulation to investigate the spin bias of low-mass halos and its connection to the strong clustering of ultra-diffuse galaxies (UDGs) reported by Zhang et al. (2025). By comparing two halo spin definitions—one using only bound particles ($\lambda_{\rm b}$) and another including unbound particles ($\lambda_{\rm a}$)—we demonstrate that the spin bias of low-mass halos...

Circumbinary planets (CBPs), planets orbiting binary star systems, offer unique insights into planet formation. However, they are challenging to detect using traditional methods. While photometric surveys such as Kepler and TESS have led to the discovery of around a dozen transiting CBPs, the majority of these systems lack precise mass measurements due to limitations of transit-based methods....

Direct imaging of exoplanets using ground-based telescopes requires coronagraphs operating at deep contrast together with precise wavefront control. While state-of-the-art extreme adaptive optic systems remove the majority of wavefront aberrations caused by atmospheric turbulence, residual errors remain causing leakage of starlight and decreasing the coronagraphic performance. Additional...

Pebbles, solid particles weakly coupled to the gas, are considered a key ingredient in planet formation, enabling both the onset of the streaming instability and the subsequent growth of planetary embryos through pebble accretion. For particles to partially decouple from the gas, they must be sufficiently compact. In contrast, the particles produced naturally from dust coagulation are highly...

Conventional coronagraph architectures struggle to reach the theoretical limit of exoplanet detection when the exoplanet is close to the star, particularly when the telescope has a complex aperture or when the star itself is partially resolved. Coronagraphy or nulling using spatial mode-sorting is capable of reaching the theoretical limit, but the optimal solution has so far only been...

The Milky Way is expected to contain many ultra-compact binaries (UCBs) with orbital periods on the order of hours. Due to the relatively high wavelengths of these signals these are not detectable by ground-based gravitational wave (GW) detectors, but will be in the range of the future Laser Interferometer Space Antenna (LISA). LISA will be used to construct a catalog of the different UCB...

High contrast imaging from the ground requires extremely sensitive wavefront sensing to correct the effects of the atmosphere. While the information limits of a wavefront sensor are well known, a practical, robust design that saturates these limits remains elusive. Furthermore, previous work often ignores the effects of amplitude aberrations (scintillation) when considering the fundamental...

We are currently at the dawn of a new era in multi-messenger astrophysics. Imaging air-Cherenkov telescopes such as MAGIC, H.E.S.S., and VERITAS have already detected around 90 active galactic nuclei (AGN) at TeV energies, while neutrino observatories like IceCube and KM3NeT have identified several high-energy neutrinos likely associated with AGN. A key open question remains: where in the jet,...

Radio waves emitted by pulsars experience a frequency-dependence propagation effect caused by free elections in the ionized interstellar medium (IISM), parameterized by the dispersion measure (DM). Temporal variations in the DM of pulsars provide a powerful probe of the density fluctuations of the free electrons in the ionized interstellar medium. These variations provide insight into the...

The Near-Ultraviolet eXplorer (NUX) is a proposed ground-based observatory that will operate at 300-350 nm to survey fast, hot transient sources. At the moment, its scientific and technical feasibility is being tested with a prototype system called Proto-NUX. The main purpose of Proto-NUX is to find the atmospheric throughput and variability in the 300-350 nm band, and to determine the...

In anticipation of the Square Kilometre Array Observatory, especially its lower range components coming online in the next few years, it is expected that this radio telescope is sensitive enough to detect radio signals from pulsars at greater distances in the universe. Particularly pulsars close to the SMBH Sgr A* are of great interest as time delay effects from their signals can give greater...

Fast radio bursts (FRBs) are transient radio events of extragalactic origin whose sources remain uncertain. As their signals propagate over cosmological distances, they are modified by a range of propagation effects along the line of sight, including dispersion from free electrons and frequency-dependent scattering due to multipath propagation. Isolating the propagation effects local to the...

Accurate pulsar astrometric estimates play an essential role in almost all high-precision pulsar timing experiments. Traditional pulsar timing techniques refine these estimates by including them as free parameters when fitting a model to observed pulse time-of-arrival measurements. However, reliable sub-milliarcsecond astrometric estimations require years of observations and, even then, power...

By harnessing the unique capabilities afforded by optical interferometry, VLTI/GRAVITY+ has recently become a powerful new tool for the direct detection and characterisation of exoplanets. Its extreme astrometric precision allows us to accurately constrain orbital geometries and dynamical masses just as its direct K-band spectra permit peering into the atmospheres of these objects. On top of...

Ram-pressure stripping (RPS) is an environmental process that transforms galaxies as they travel at high velocity through the hot gas in clusters and groups by removing their interstellar medium, forming one-sided tails. With radio continuum observations, we can detect the non-thermal component, i.e. the cosmic ray electrons and magnetic fields, in the stripped tails. Since the process of...

In 2020 the sustainability committee of the Dutch Astronomy Council published an inventory of CO2 impact of astronomy in 2019. In the strategic plan for astronomy 2021-2030 a significant reduction of the CO2 impact was announced. We present an update on the CO2 emissions of Dutch astronomy, in particular related to air travel and discuss this in the context of the announced CO2 reductions.

LOTAAS, the LOFAR Tied-Array All-Sky Survey, offers an extensive dataset for discovering low-frequency radio transients. However, the original single-pulse search was not optimized to detect longer-duration or heavily scattered signals, and was limited by high false positive rates arising from instrumental variability and RFI. Since then, our understanding of FRBs at low frequencies has...

Long-period transients (LPTs) are a recently identified class of coherent radio transients with durations ranging from a few seconds to several minutes, and periodicities on timescales of minutes to hours. To date, only twelve such sources have been reported, with few confirmed to reside in white dwarf–M-dwarf binary systems. The absence of detected optical companions or detection of X-rays in...

Fast radio burst surveys are typically optimized for millisecond-duration events, leaving the parameter space of longer-duration coherent radio transients relatively unexplored. In this work, we investigate the selection function of the CHIME/Slow pipeline. CHIME/Slow is built on the wide-field 400–800MHz Canadian Hydrogen Intensity Mapping Experiment (CHIME) and extends transient searches to...

Binary neutron star (BNS) mergers are among the most information-rich events in modern astrophysics, producing a unique combination of multi-messenger signals including gravitational waves, short gamma-ray bursts, and kilonovae. These signals probe some of the most fundamental open questions in physics: the neutron star equation of state, r-process nucleosynthesis, and the origin of...

55 Cnc e is the first rocky exoplanet for which strong evidence of a thick, volatile atmosphere exists (Hu+2024). The atmosphere of this hot super Earth shows sub-weekly variability in emission (Demory+2016, Meier-Valdez+2023, Patel+2024). Among the multiple suggested scenarios is an outgassing – cloud formation cycle driving this variability. We investigate, whether lava worlds could host...

Planet formation is an important topic, but how planets are forming in protoplanetary disks is still not fully understood. Silicate monomers (um-sized) are present in the disk and may attach to each-other to form fluffy, porous aggregates, which may then further progress into more solid pebbles, into planetesimals or protoplanets through a variety of proposed pathways. The material properties...

Just over a decade ago the first X-ray pulsations were discovered in an Ultraluminous X-ray source (ULX), revolutionizing our understanding of these systems. The detection of pulsations showed at least some ULXs offer us ideal laboratories to study the most extreme manifestation of accretion onto neutron stars (NSs), even if the number of NS-ULXs within the ULX population remains uncertain....

Mass transfer from a thermally pulsing (TP) asymptotic giant branch (AGB) star is a common phase in the evolution of low- and intermediate-mass binary systems. When carbon and s-process-enriched material is transferred from the TP-AGB star to a relatively unevolved companion, the accretor can become a barium- or carbon-enriched star. Observationally, such systems are found in binaries with...

The importance of stellar magnetic activity to research space weather is increasingly recognised. Long-term monitoring campaigns in the radio regime remain sparse, but are necessary to observe stellar radio bursts, radio flares or potentially interactions with the magnetic fields of exoplanets.
The binary system EQ Pegasi is known to exhibit strong and frequent radio emission driven by...

All GRMHD models employed by the Event Horizon Telescope to interpret horizon-scale emission from Sagittarius A and M87 develop magnetically driven polar outflows. These simulations are scale-free and can be rescaled to different black hole masses and accretion rates, making them an ideal framework to test the unification of accretion physics across mass scales. In this work, we investigate...

Black hole low-mass X-ray binaries (BH LMXBs) are transient sources which spend most of their lifetime in quiescent states. Once or twice a year they are characterised by bright outbursts that last for days to months, during which accretion flow, compact jets and discrete ejecta undergo significant evolution. These relatively short outburst timescales make BH LMXBs ideal natural laboratories...

Surface Brightness Fluctuations (SBF) provide redshift-independent galaxy distances and probe stellar populations through pixel-to-pixel brightness variations. With the high resolution Euclid data it is now possible to use this method to determine distances of dwarf galaxies in the whole Local Universe up to 50 Mpc.
In this work, Euclid data is used to measure SBF magnitudes and colors for...

Mass transfer is arguably one of the most important aspects in the evolution of binary stars, with the majority of binaries having at least one episode of mass transfer during their lifetime. Yet its efficiency — the fraction of the transferred mass that is accreted — remains plagued by uncertainties, despite dictating the outcomes of mass transfer and predicted populations of stripped-star...

Fast radio bursts (FRBs) are millisecond-duration radio transients of extragalactic origin whose progenitors and emission mechanism(s) remain mysterious. Of the ~4000 FRBs discovered to date, only ~100 repeat, raising the question of whether repeating and apparently non-repeating FRBs arise from the same underlying population.

I present recent milliarcsecond localisations of FRBs that...

Each stars is expected to have a planetary systems, and most stars end up as a white dwarf. The evolution of a star into a white dwarf has a significant impact on the planetary system. With large sky surveys, we are now starting to see signs of the (disruption of) planetary systems around white dwarfs. This includes enrichment of the white dwarf atmosphere by planet material, engulfment of...

The Dutch Research Council (NWO) is one of the most important science funding bodies in the Netherlands and realises quality and innovation in science. Each year, NWO invests almost 1 billion euros in curiosity-driven research, research related to societal challenges and research infrastructure.
Are you wondering what kind of different funding instruments are available at NWO? How they are...

It is well known that dense environments like clusters play a role in galaxy evolution, showing an increase in quenched galaxies with an increase in density. However, the exact mechanisms involved in quenching these galaxies are not well understood, and there is also evidence indicating that some galaxies experience preprocessing before falling into the cluster. To investigate this, I present...