Netherlands Astronomy Conference 2025

Planet-forming disks go from gas-rich, massive disks made of dust and gas into planetary systems containing only small amounts dust. This dust is produced by collisions between smaller planetary objects, such as planetesimals, asteroids, and comets. Traditionally, we talk about protoplanetary (age ~1 Myr), transitional (~5-10 Myr), and debris disks (~10-hundreds of Myr) even though the overlap...

For many years now pebble accretion is recognized as perhaps the fastest growth mechanism in planet formation. Yet until now most studies have only considered a single pebble size (monodisperse) for calculating the growth rate of the planet. Pebble accretion works because specifically the pebble-sized solids are loosely coupled to the gaseous disk. The mechanics of these loosely coupled...

Fast radio bursts (FRBs) – millisecond-duration, luminous radio transients – remain one of the biggest mysteries in modern astrophysics. While thousands have been detected, their sources and emission mechanisms are still widely debated. Precise localization is crucial for understanding the environments of FRBs, and very long baseline interferometry (VLBI) provides an unparalleled tool for...

As gravitational wave detectors become more sensitive, they will detect so many sources that individual events blend together to form a stochastic Gravitational Wave Background (GWB). Detecting anisotropies in this background could provide valuable insights into various cosmological and astrophysical properties. Given the strong expectation that LISA will detect the astrophysical GWB created...

Many studies have shown that the presence of gas and metals influences the amount of dust observed within galaxies. These studies rely on assumptions of how the metallicity varies within the disk and whether the gas and its location relative to dust. These assumptions are often based solely on observable vicinity within the Milky Way limited by extinction. That is why spatially resolved...

Studying the hot ($T=10^6$ K) gas phase of the circumgalactic medium (CGM) around late-type galaxies is crucial due to its connection to the missing baryon problem and the open question of how gas accretes onto galaxies to sustain star formation.
We use a simple semi-analytic model assuming hydrostatic equilibrium, radiative cooling and mechanical heating from a central source, to evolve the...

Molecules can be used as tracers for various quantities in various astronomical objects. The stability, variety, and ubiquity of Polycyclic Aromatic Hydrocarbons (PAHs) make them especially useful as these astronomical tools. In this work, the model ALPAHCAS is presented that accurately calculates the mid-infrared spectra of PAHs. These spectra are then used for various applications. One of...

Our rapidly increasing observational capabilities for exoplanet characteristics increasingly challenge current modeling tools. Simplifications we make to our atmospheric modeling cause biases in the derived parameters. Especially the unprecedented accuracy of JWST observations show us that often taking into account inhomogeneous, 3D and cloudy atmospheres is no longer a luxury, but a...

Cepheid variable stars are well-known optical and infrared targets, as their period-luminosity relation is an essential rung on the distance ladder, especially in the IR K-band. However, millimeter and sub-millimeter observations of these objects are rare. We present VLA and ALMA observations of Cepheids covering 20 and 260 GHz (down to the radio K-band). Three Cepheids show tentative emission...

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....

Thermonuclear (type-I) X-ray bursts arise from unstable ignition of accumulated material on the surface of neutron stars in low-mass binary systems. Despite many decades of observations, we still lack a complete explanation of the remarkable diversity of burst properties. One of the key inputs is the composition of the fuel accreted from the binary companion, which along with the accretion...

Titan’s upper atmosphere is a key site for studying complex organic chemistry in a cold, oxygen-poor environment, with strong relevance to both planetary science and prebiotic chemistry. PAHs (Polycyclic Aromatic Hydrocarbons) have been detected there previously, but questions remain about their size, formation, and evolution. In this work, we reanalyze Cassini VIMS limb spectra using an...

Intermediate redshift (z~0.5) galaxy clusters contain many more blue galaxies than present-day clusters (Butcher & Oemler 1978). However, it is still unclear whether the truncation of star formation in galaxies (referred to as quenching) is trigger by internal (e.g. AGN feedback) or external environmental processes. This Masters project aims to constrain the timescales and mechanisms...

With high-quality data and a large sample from Euclid, providing powerful statistical insights, this project aims to quantify how the fraction of dust-obscured star formation varies with stellar mass and evolves over cosmic time. Dust plays a crucial role in the evolution of massive galaxies, strongly correlating with stellar mass and affecting our ability to trace star formation history....

Black holes represent some of the most extreme environments in the universe, spanning vast ranges in mass, size, and energy output. Observations from the Event Horizon Telescope (EHT) have provided an unprecedented opportunity to directly image black holes, with future plans aiming to create time-resolved movies of their evolution. To fully leverage these observations, we need theoretical...

Ionized outflows are multiphase plasma streams extending from hundreds to thousands of parsecs from active galactic nuclei, representing a critical mechanism of galactic evolution. These complex gas flows, characterized by velocity ranges of 100-3000 km/s and diverse ionization states, play a crucial role in shaping galactic evolution and structure by removing or heating gas, starving galaxies...

The Habitable Worlds Observatory (HWO) is the next flagship of NASA. The telescope will be a successor to HST with a wavelength coverage from the UV to the near-IR. Its ultrastable ~6-7 meter aperture with high contrast imaging capabilities will allow direct characterization of Earth sized planets within the habitable zone of solar type stars. However, the high contrast imaging instrument is...

Despite an increasing recognition of the importance of stellar magnetic activity for determining the space weather exoplanets experience, long-term radio monitoring campaigns of active radio stars remain sparse. At the same time, the Westerbork Synthesis Radio Telescope (WSRT) is currently underutilized. We know that magnetically active low-mass stars produce radio flares that can interact...

To date, image plane transients found in LOFAR observations are found weeks to months after the observation took place. This significantly hinders obtaining multi-wavelength follow-up observations that are vital in determining the progenitor of the transient and characterising its properties. Instead, we want to be able to find the brightest transient sources, particularly the long period...

Tidal Disruption Events (TDEs) occur when a star is torn apart by the tidal forces of a supermassive black hole, producing a luminous flare that evolves over weeks to months. These transients are valuable for studying astrophysical jet launching, accretion disk formation, and supermassive black hole demographics. The classification of these sources typically requires spectroscopic follow-up,...

Distant quiescent galaxies provide crucial insights into the formation of massive galaxies in the local universe, as they had already ceased star formation when the universe was only a fraction of its current age. To better understand this population, we analyze galaxies from the Heavy Metal survey consisting of 20 massive quiescent galaxies at $1.3<z<2.3$. Half of these galaxies have been...

One of the key open questions in black hole astrophysics is the nature of the electron distribution function (eDF) in accretion flows, specifically: how are electrons heated and accelerated, and how does this affect the observed emission? Answering this question is crucial for interpreting multi-wavelength observations of active galactic nuclei (AGN) and understanding the connection between...

Research in Diffuse Interstellar Bands (DIBs) has been ongoing for over a hundred years, but still little is known about their carrier molecules. Now a new study tries to shed a light on this. The EDIBLES study collects high quality spectra of DIBs in over a hundred different sightlines. Since the inception of the study in 2017 over 10 papers have been published using the EDIBLES study as a...

Planets form in discs of gas and dust around young stars. Within these discs, micron-sized dust particles need to clump together and grow 14 orders of magnitude to form planets. Collisions between dust particles can lead to growth or fragmentation, changing the dust size distribution. The state of the art in coupling dust coagulation to hydrodynamics are 2D simulations with ∼100 particle size...

The Thousand Pulsar Array (TPA) program provides a large pulsar dataset that has been collected over five years with MeerKAT, the most sensitive radio telescope in the Southern Hemisphere. Beyond its primary goals of studying pulsar emission and population statistics, the TPA program also enables the analysis of the interstellar medium (ISM) - a crucial step toward understanding the electron...

According to general relativity, gravitational waves (GWs) should travel at the speed of light. However, different theories beyond General Relativity predict possible deviations from the speed of light, and some even introduce dispersion effects $ E^2 = p^2 + \mathbb{A}_\alpha p^\alpha $, where $\alpha = 0$ corresponds to the case where the graviton has mass $\mathbb{A}_0=m_g^2$. Comparing the...

The Galactic magnetic field plays a crucial role in many astrophysical processes in our Milky Way such as star formation and cosmic-ray propagation. It fulfills multiple roles: for example, it maintains the energy balance in the Milky Way and transports angular momentum. Understanding the Galactic magnetic field is important, as it affects many observations from outside of our Milky Way, such...

To distinguish halo stars from stars in the thin and thick disk, the velocities of the stars are often used, such as applying a cutoff to the Toomre velocity. Gaussian Mixture Models (GMMs) are also used to model the contributions from the three components. However, a Toomre velocity cutoff is somewhat rudimentary, and the GMMs assume that the velocity distributions of all three components are...

We present preliminary streamline calculations for a parcel of gas in radiatively
driven outflows from accretion disks around active galactic nuclei (AGN). This is done by explicitly
calculating the photoionization balance of the wind at each point (r, ϕ, z) along a given streamline
trajectory. The force multiplier, a measure of the distribution of dimensionless line strengths at a
given...

On the 25th of August 2024, the Swift telescope detected Gamma-Ray Burst
GRB 240825A at a redshift of 0.659. The X-ray Telescope (XRT) on board,
localised the source in the Pisces constellation with an uncertainty of
0.0014 degrees. The High Energy Stereoscopic System (HESS), Fermi, Rapid
Eye Mount telescope (RAPAS) and ALMA, among many others, followed up and
observed GRB 240825A and its...

Cassiopeia A (Cas A) is the youngest core-collapse galactic supernova remnant (~350 yrs) and is amongst the closest known (~3.4 kpc). It has a secure supernova classification of Type IIb using light echo spectroscopy analysis. These make it an ideal source for studying supernova ejecta properties and its velocity distribution. We map the plasma properties of Cas A using two observations from...

Fast radio bursts (FRBs) are enigmatic millisecond-duration radio transient flashes of extragalactic origin. Studying burst properties such as dispersion measure allows us to probe the turbulent and dynamic local environments of FRBs.
FRB 20240619D is a repeating FRB source discovered with MeerKAT in 2024. Within hours of its publication, we initiated a high-cadence monitoring campaign as...

The Square Kilometre Array (SKA) is a 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.
With such an extreme antenna density, surpassing e.g. LOFAR by two orders of magnitude, this observatory is well equipped to make the most precise...

We investigate the acceleration and transport of electrons in the highly fine-structured current sheet that develops during magnetic flux rope (MFR) eruptions. Our work combines ultra-resolved MHD simulations of MFR eruption, with test-particle studies performed using the guiding center approximation. Our grid-adaptive fully three-dimensional, high-resolution magnetohydrodynamic simulations,...

Using GRMHD, we are studying particle acceleration of a jet launched after a binary neutron star merger.

Protoplanetary disks observed in scattered light reveal essential insights into the disk’s three-dimensional architecture and
dust properties. These disks, which play a crucial role in planet formation, have complex structures where the visibility of the disk’s
backside can vary significantly based on several parameters.
Aims. We aim to explore the factors impacting backside visibility in...

Recent detections of free-floating planets have provided insights into planetary formation and dynamics. These rogue planets, which do not orbit a host star, are thought to form primarily from dynamical ejections during close stellar encounters. The giant planets in the Solar System have moons, raising the question: what happens to the moons of these ejected planets? In this study, we perform...

Gaia has shown the scientific value of precision absolute and relative astrometry. Libralato et al. 2024 show the scientific potential of combining stellar astrometry from Gaia and Euclid to constrain through relative astrometry the kinematics of globular clusters.
The question of our project is: how to best obtain an absolute astrometric reference frame by combining Gaia and Euclid data on...

Low-mass X-ray binaries (LMXBs) provide an excellent laboratory for studying accretion physics and jet launching due to their rapid variability, which occurs on much shorter timescales than in supermassive black holes (SMBHs). This variability enables direct investigation of the interplay between accretion and jets, a fundamental open question in high-energy astrophysics, by linking X-ray...

Titan's dense atmosphere and complex organic chemistry make it a prime candidate for investigating prebiotic processes beyond Earth. In this project, we investigate the role of Galactic Cosmic Rays and solar wind particles in processing molecular ices relevant to Titan’s atmosphere. Pure ices of phenanthrene (C₁₄H₁₀), acetonitrile (CH₃CN), and their 1:1 mixtures were deposited in situ onto a...

We investigate the radiative properties and multiwavelength variability of two-temperature black hole magnetically arrested disks (MADs) for two spins ($a_*=0\;\&\;0.94$). Using a Monte-Carlo approach, we compute full spectral energy distributions (SEDs), including synchrotron, inverse-Compton, and Bremsstrahlung radiative processes. Spectra are dominated by synchrotron and 1st-order Compton,...

Low-luminosity active galactic nuclei (LLAGN), loosely defined by bolometric luminosities below L$_{\text{bol}}$ < 10$^{44}$ erg s$^{-1}$, constitute the majority of the local AGN population. These systems are assumed to accrete at lower rates, resulting in possible state changes such as radiatively inefficient accretion flows, non-thermal continuum emission, and a jet-dominated structure...

The origin of high-energy cosmic rays remains one of the biggest mysteries in astrophysics. Mass reconstruction of the primary cosmic ray is essential for pinpointing potential sources. In this study, we utilize hadronic interaction models—EPOS, SIBYLL, and QGSJET—to simulate extensive air showers. By analyzing the resulting observables, we aim to establish a robust method for distinguishing...

When a star passes close to massive black hole, it is tidally disrupted, yielding a bright transient that can be detected at optical wavelengths. Over the past decade, many of these Tidal Disruption Events (TDEs) have been discovered. A puzzling property of their host galaxies is the observation that most TDEs are found in the so-called green valley of the galaxy distribution. The nature of...

Omega Centauri (NGC 5139), the most massive globular cluster in the Milky Way, with a recently identified IMBH at its core, represents an unique opportunity to study both dark matter and millisecond pulsars populations. Due to its unique view on the southern sky, the H.E.S.S. TeV gamma rays detector in Namibia is currently observing this region. In this work we will present the H.E.S.S....

We present a comprehensive analysis of the spectro-temporal characteristics of the X-ray variabilities from black hole X-ray binary 4U 1630-472 during its three outbursts (2018, 2020, and 2021) as observed by NICER.
We detected 27 Quasi-Periodic Oscillations (QPOs), out of which 25 were observed during the 2021 outburst. In this study, we specifically focus on the relationship between...

Extra-galactic Fast X-ray Transients (FXTs) are X-ray flashes lasting minutes to hours in the soft X-ray regime (i.e., 0.3-10 keV). Their nature is unclear, but the most remarkable scenarios related to them are shock breakout supernovae, tidal disruption events involving white dwarf stars and intermediate massive black holes, binary neutron star mergers, and high-redshift gamma-ray bursts....

We present the Near-Ultraviolet eXplorer (NUX), which will consist out of 4 small (36 cm diameter) groundbased telescopes that are optimized for the shortest wavelengths that are detectable from Earth (i.e., the near-UV [NUV] wavelength range of 300-350 nm). Each telescope will have a field-of-view of ∼17 square degrees sampled at ∼2.6”/pixel, and will reach a NUV magnitude (AB) of 20 in 2.5...

The majority of the massive OB-type stars (M $\geq$ $8M\odot$) are found in OB associations confined to the Galactic plane. Most of these massive stars are in binaries. If the binary is tight enough, a phase of mass transfer occurs when the initially most massive star (the primary) expands and fills its Roche lobe. As a consequence, the mass ratio inverts and the secondary becomes the most...

The Cherenkov Telescope Array (CTA) is the next generation ground-based TeV gamma-ray observatory comprising three telescope sizes: small, medium, and large, with an energy sensitivity ranging from 20 GeV to 300 TeV. CTA will be deployed across two locations: Paranal, Chile; and La Palma, Spain, providing full coverage of the entire sky. With a 4 m primary reflector, the Small Sized Telescopes...

Cold molecular gas is the fuel for star formation. Tracing the evolution of the cosmic density of molecular gas is therefore key to understanding the physical processes that drive galaxy formation through cosmic time, including the star formation rate density and the baryon cycle of matter in and out of galaxies. In the last decade, spectral scan surveys on all large interferometers (ALMA,...

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...

Extra-Galactic fast X-ray transients (FXTs) are X-ray flashes lasting from a few seconds to several hours. Their progenitor mechanism remains largely unclear, but likely comprises a mix of possibilities, including binary neutron star mergers, tidal disruption events involving a white dwarf and an intermediate-mass black hole, supernova (SN) shock breakouts and gamma-ray bursts (GRBs) with...

Planetary systems present remarkable diversity, yet the underlying processes that shape this diversity remain poorly understood. The prevailing theory suggests that planets form within circumstellar disks, where gas and dust coagulate into planetary bodies. Planetary population synthesis models attempt to replicate this process by simulating planet formation under varying physical conditions....

Edge-on disks provide a unique opportunity to probe the vertical structure and solid-state composition of protoplanetary environments. Recent JWST observations of the binary disk HH 48 have demonstrated that 3D radiative transfer models incorporating full anisotropic scattering are essential for accurately retrieving ice abundances (Sturm et al. 2023b, 2024; Bergner et al. 2024). In HH 48 NE,...