Netherlands Astronomy Conference 2025

As KNA/RNAS Chair I wish to open the conference, during a 10min presentation in which I also shall recall the WWII episode of the Society. After the 10min I will hand over to the LOC Chair.

HARPS3 is a high resolution (R~115,000) stabilized Doppler spectrograph covering a wavelength range from 380-690nm with polarimetric capabilities that is coming online on the roboticized 2.5m Isaac Newton Telescope (INT) at La Palma in Fall 2025. HARPS3 is designed to enable ~10cm/s radial velocity (RV) precision on nearby bright solar-type stars to enable the detection of Earth Twins. The...

I will present the status of WEAVE, the new wide-field spectroscopic survey facility for the William Herschel Telescope at the ING, and some early science results. WEAVE has been operational in its Large Integral-Field Unit (LIFU) mode since late 2022 and is presently commissioning its MultiObject Spectroscopy (MOS) and mini-IFU (mIFU) modes. I will present the instrument performance in the...

One of the remaining unsolved questions is the one of globular cluster formation, as there is still no definite consensus on whether the clusters have formed within the Milky Way galaxy (in situ) or have been accreted. Current estimates suggest that between 25-65% of all Milky Way GCs were accreted, however the exact number is still uncertain. Since GCs are significantly old (up to 12 Gyr),...

In June 2023, International Pulsar Timing Array (IPTA) collaborations in Europe, America, India and Australia simultaneously announced the first compelling evidence of the low-frequency (nHz) gravitational wave background. This was a milestone in gravitational wave astronomy. These results were further strengthened by detailed comparative analysis at the IPTA level. The main source of noise in...

Astrophysical research is increasingly leveraging data science, statistics and machine learning, with applications ranging from detecting transients in images to inferring exoplanet atmospheres. However, studying the most energetic phenomena in the universe presents particular challenges, including comparatively small, heterogeneous datasets and a lack of reliable training data. This talk...

Fast radio bursts (FRBs) are one of the most exciting mysteries in contemporary astrophysics. They last only a fraction of a second but are bright enough to be detectable from halfway across the Universe. FRBs are unique astrophysical tools: they are perfect point sources, impulsive, and being in the radio band they are also distorted in ways that carry valuable information about otherwise...

Massive stars are chemical factories, they are progenitors of supernovae, neutron stars and black holes, and they play a crucial role in the formation and evolution of their local environment as well as their entire host galaxies. Given their prevalence in close binary systems, at the end of their lives they may produce double-compact objects, which are potential gravitational-wave sources....

Exoplanets are not only ubiquitous, but diverse in nature. The mechanisms governing their formation and evolution remain elusive, yet theoretical modelling suggests that the atmospheres of gaseous worlds can offer clues into their history. However, due to the required precision on these measurements, studying planets individually is not sufficient to test these models: one must conduct...

Gravitational waves (GW) are providing a new way to study the properties of compact objects. In this context, understanding what determines the final fate of stars, the role of binary interactions, and which signatures to expect in GW observations is becoming increasingly important. The formation of black holes (BHs) or neutron stars (NS) is not a simple function of the initial mass of a...

How the chemistry in the universe evolves from diffuse interstellar medium to a life-harboring environment on our Earth? Complex organic molecules (COMs), typically defined as carbon-bearing molecules with at least six atoms, have gained their popularity over the past several decades due to their importance of linking atoms and simple molecules with prebiotic species. COMs are suggested to be...

In the past decade, hundreds of exoplanets have been discovered in extremely short orbits below 10 days. Unlike in the Solar System, planets in these systems orbit their host stars close enough to disturb the stellar magnetic field lines. The interaction can enhance the star's magnetic activity, such as its chromospheric and radio emission, or flaring. So far, the search for magnetic...

Accretion and outflows are astrophysical phenomena observed across a wide range of objects, from white dwarfs to supermassive black holes. Developing a complete picture of these processes requires complementary studies across this full spectrum of jet-launching sources. In particular, jet–interstellar medium interaction sites near black hole X-ray binaries provide an indirect probe of the...

The Event Horizon Telescope (EHT) has imaged the black hole shadows of the supermassive black hole at the center of the galaxy M87 (M87) and at the center of the Milky Way (Sgr A), using the technique of very long baseline interferometry (VLBI) at 230 GHz. In the future, black hole imaging will transition to movie making with ground-based upgrades and extensions of the EHT array. However,...

While the political attention to it is waning, the scientific facts have not changed. Human-induced climate change is already causing damage and misery, and unless the world acts quickly and decisively, this will increase in the decades to come. The scientific information on climate change is assessed and brought to climate policymakers globally by a special organization: the IPCC. In this...

The chemical composition of tidally locked gas giant atmospheres is the result of an intricate balance between the temperature, the wind dynamics, and the incident radiation coming from the host star. As such, the planet can show distinct atmospheric signatures dependent on the phase during which it is observed. Now, with the unprecedented sensitivity of the James Webb Space Telescope, we can...

The origins of fast X-ray transients (FXTs), which are bursts of soft X-ray photons (~0.3-10 keV), have so far been amongst the most elusive of transients. Their origins in binary neutron star mergers which lead to the formation of a millisecond pulsars whose rapid spin down power the bursts; tidal disruption events (TDE) involving white dwarfs disrupted by intermediate-mass black holes; shock...

Active galactic nuclei (AGNs) play a crucial role in the coevolution of supermassive black holes (SMBHs) and their host galaxies from high redshift to the present. They influence their host galaxies through powerful winds and jets that generate massive outflows, and these feedback processes can either quench star formation by heating and expelling gas or trigger it by compressing the...

High-resolution spectroscopy (HRS) is a powerful tool for studying the atmospheres of planetary-mass objects, including brown dwarfs and exoplanets. By analysing the fine details in near-infrared spectra, we can detect absorption features from key molecules and their isotopic variants, revealing the chemical composition of these sub-stellar objects. Such measurements offer clues about their...

Dwarf galaxies play an important role when studying the effects of the environment on galaxy formation and evolution. The Fornax cluster, having a dense core and strong tidal fields, offers an ideal laboratory for investigating the influence of the cluster environment on the morphology of dwarf galaxies. We explore the relationship between the morphology of galaxies, in particular the...

XRISM, launched in September 2023, offers unprecedented capability in resolving the Fe K band. We use a deep 430 ks observation with XRISM/Resolve to investigate the AGN environment of NGC 3783 and model the structure through Fe Kα emission lines. I will present our latest results on both the narrow Fe Kα line and the relativistic broad iron line.

Our preliminary findings suggest that the...

It remains an unanswered question what dictates the amount of dust in the interstellar medium. Asymptotic giant branch stars and supernovae produce dust in their cold atmospheres, but dust gets destroyed during star-formation and supernova shockwaves. The timescales for these effects combined with the observed dust masses in galaxies implies that dust also grows in the interstellar...

Population III stars were the first generation of stars that formed in the Universe out of primordial gas. Thanks to JWST, we are now in an era where observing campaigns to discover Pop III stars has become a possibility. Over the last 3 years, several proposals on Pop III stars (from star cluster to galaxy scales) have been successful in getting time on JWST, however no convincing detections...

The recent very-high-energy (VHE; >100GeV) spectra of the afterglow emission of three gamma-ray bursts (GRBs) shake the current understanding of the underlying physics of a relativistic shock, formed at the impact surface from a plasma outflow crashing at almost the speed of light into its surrounding. I will show the limitations of established modeling and discuss new scenarios including...

Understanding the stellar mass build-up and evolution of the surprisingly massive galaxies in the Epoch of Reionization (EoR) requires insight into their molecular gas reservoirs, which fuel star formation. I will present new deep VLA observations of REBELS-25 (z = 7.31), a massive star-forming galaxy and the highest-redshift dynamically cold disk (V_rot,max/σ ≃ 11) confirmed to date. Using...

Fast X-ray transients (FXTs) are extragalactic flashes of X-rays, lasting from seconds to hours, whose nature remains largely unknown. Several progenitor mechanisms have been proposed to explain their origin, for instance, neutron star mergers, tidal disruption events involving a white dwarf and an intermediate-mass black hole, supernova shock break-out, and gamma-ray burst cocoon-like/jet...

HD 135344 is a visual binary system that is best known for the protoplanetary disk around the secondary star. Various substructures, such as a cavity and spiral arms, point to ongoing planet formation, but putative planets have remained hidden. The circumstellar environment of the A-type primary star, on the other hand, has evolved faster as inferred from the absence of accretion and...

Cygnus A (CygA) is one of the most famous radio sources, and it has clear evidence of the central active galactic nucleus (AGN) interacting with its environment. The AGN is driving a cocoon shock that adds $10^{60}-10^{61}$ ergs of energy into the cluster gas surrounding CygA. The proximity of CygA ($z=0.0561$) allows us to answer two critical questions in cluster physics: (1) Which processes...

This talk introduces ShadowSWIFT, a novel moving-mesh hydrodynamical code for large-scale cosmological and galaxy simulations, developed within the SWIFT collaboration. SWIFT is a highly optimised and scalable software that allows hydrodynamical solvers to use multiple subgrid routines. ShadowSWIFT is currently compatible with the EAGLE and GEAR subgrid routines, and is expected to release...

Recent direct imaging surveys like YSES and BEAST have revealed a population of young, super-Jupiter exoplanets at extreme distances from their host stars (>100 AU). These discoveries challenge planet formation theory which struggles to explain how such massive planets are formed so far away from their stars. Proposed mechanisms include in-situ formation through cloud fragmentation or disk...

The Event Horizon Telescope (EHT) has enabled horizon-scale imaging of supermassive black holes. However, constraining black hole spin remains a challenge, despite its importance for testing accretion physics, jet launching, and gravity. Therefore, it is worthwhile to investigate new methods for determining spin, particularly those that make minimal assumptions about the complex astrophysics...

Wide field surveys searching for transiting exoplanets also record and discover both known stellar variability and previously unknown phenomena. Deep and complex eclipses of otherwise unremarkable stars reveal eclipsing companions that have complex substructures. The ASAS-SN survey has now produced over a dozen complex eclipses that last from weeks to years, and we present our analyses of...

Numerous theoretical studies within the modern cosmological framework suggest that gas accretion from the intergalactic medium is essential to feed star formation in galaxies throughout cosmic time. However, the way gas accretion takes place is still poorly understood as a direct evidence of it is still lacking. In some models, gas accretion is expected to take place in the outer discs of...

Coronal mass ejections (CMEs) are a dominant contributor to space weather in the Solar System, with the potential to erode planetary atmospheres. While traditional stellar activity indicators, such as flares, do not confirm the presence of a CME, Solar studies have established that Type II radio bursts provide a direct signature of CME-driven shocks. However, despite extensive searches, no...

Ultra-high-energy cosmic rays are the highest energetic particles known - and yet their origin is still an open question. This is mainly because they are deflected by cosmic magnetic fields during their travel from the sources to Earth, so that their direction of arrival does not correspond to the direction of the source. At the Pierre Auger Observatory, several quantities of ultra-high-energy...

Construction of low frequency component (50 - 350 MHz) of the Square Kilometre Array has started in Australia. With an immensely dense core of almost 60 thousand antennas within a square kilometer, the telescope provides a unique opportunity to study cosmic rays in the energy range between 10$^{15}$ and 10$^{18}$ eV. High resolution observations and new analysis strategies will provide more...

In this talk, I will introduce the Resolved Cluster Evolution Sunyaev-Zeldovich Survey (ReCESS): a 200-hour-plus observing campaign aimed at resolving the intracluster medium (ICM) through the thermal Sunyaev-Zeldovich (tSZ) effect in 25 ACT-selected galaxy clusters within a redshift range of 1.2 < z <2.0 using MUSTANG-2 on the GBT and ALMA. I will present the first results on the average...

The equatorial jets observed on the Jovian planets—Jupiter, Saturn, Uranus, and Neptune—exhibit extreme zonal flow patterns, manifesting as either strongly prograde or strongly retrograde (Ingersoll, 1990). Existing theories have often treated gas giants and ice giants separately, primarily focusing on the shallower atmospheric layers of the ice giants (e.g., Schneider and Liu, 2009; Liu and...

The Radio Detector (RD) at the Pierre Auger Observatory is a new large-scale instrument designed to measure the highest-energy cosmic rays. It consists of 1660 radio antennas spread across 3000 km², detecting the radio emission from extensive air showers in the 30–80 MHz range. By combining these measurements with data from water-Cherenkov detectors, we can determine both the energy and...

Many close-in exoplanets are expected to orbit inside the Alfvén surface of the stellar wind, the region where the stellar wind is dominated by the stellar magnetic field. In this scenario, the planet acts as an obstacle to the stellar wind flow, leading to an electromagnetic coupling between the star and the planet. The energy fluxes arising from this interaction can power enhanced emission...

Mass and angular momentum regulate most of their formation and evolution of galaxies, including their morphological, kinematic, and star-forming properties.

In this talk, I will present our recent results characterising the angular momentum of the molecular gas in nearby disc galaxies. Exploiting data from the PHANGS-ALMA survey, we have performed the first statistical study of the...

Context. Type III solar radio bursts are among the most common radio emissions from the Sun, produced by energetic electron beams propagating through the solar corona and interplanetary space. These bursts are characterized by their rapid frequency drift, and through them, we can further study solar activity. Since the launch of ESA’s Solar Orbiter mission in 2020, the Radio and Plasma...

We present two new radio continuum images obtained with Apertif at 1.4 GHz. The images, produced with a direction-dependent
calibration pipeline, cover 136 square degrees of the Lockman Hole and 24 square degrees of the ELAIS-N fields, with an average
resolution of 17×12′′ and residual noise of 33 μJy/beam. With the improved depth of the images we found in total 63692 radio
sources, many of...

The Radar Echo Telescope for Cosmic Rays (RET-CR) is a prototype experiment for the future neutrino detector, the Radar Echo Telescope for Neutrinos (RET-N). It is deployed at Summit Station in Greenland, with an entire data-taking run conducted in the summer of 2024.

RET-CR explores the possibility of the long-term goal for RET-N, hence advancing neutrino astronomy with new detection...

The Solar and Heliospheric Observatory (SOHO) Extreme-ultraviolet Imaging Telescope (EIT) has been taking images of the Solar disk and corona in four narrow EUV bandpasses (171, 195, 284, and 304 angstroms) at a minimum cadence of once per day since early 1996. The time series of fully-calibrated EIT images now spans approximately 28 years, from early 1996 to the early 2024, covering solar...

Cataclysmic variables, accreting white dwarfs in binaries, can zoom into and out of view of our telescopes in a matter of days or weeks, first brightening then fading, only to repeat this later the same year. This timescale of variability is a sign of the dwarf nova, a class of cataclysmic variable. The dwarf nova outburst is a change in the accretion disc of these systems, which not only...

Light pollution not only disrupts ecosystems and human health but also severely impacts astronomical observations by increasing skyglow, limiting our ability to study the universe. DARKER SKY is an Interreg North Sea project dedicated to reducing light pollution to enhance biodiversity and ecological connectivity across the North Sea region. It has a budget of €4.2 million and involves 13...

Direct imaging is a technique that allows us to spatially resolve the planet from its host star. Due to the big difference in flux between star and planet, a very high contrast must be reached to observe the planet that would be otherwise hidden in the glare of the star.

Coronagraphs are optical systems that work as angular filters, suppressing the on-axis star light and letting the...

In this talk, I will give an overview of the IT research services at SURF that are relevant for astronomy research. In paricular, which solutions are there for large-scale simulations, high-throughput data processing and data storage and management? And how can you get (free) access to the national Computing facilites at SURF or, for even larger needs, to Europe’s fastest supercomputer LUMI.

Pulsar Timing Array (PTA) projects hold the promise of becoming sensitive Gravitational-Wave (GW) detectors in the nanoHertz frequency band. Multiple international PTA collaborations are actively timing an array of pulsars with their respective radio observatories, and each collaboration carries out GW searches in their own data. In principle, a combined search over all available PTA data is...

The design of the Multi-Object Spectrograph (MOS) for Astrophysics, Intergalactic-medium studies and Cosmology (MOSAIC) for the Extremely Large Telescope (ELT) is optimized for key capabilities such as high survey efficiency, high sensitivity to faint targets, and covering an extended parameter space, in terms of available modes (MOS & mIFU), bandwidth, spectral resolution, for the wavelength...

In this presentation, we will share the first results of our project to reach underrepresented school children with our interactive planetarium shows. The NOVA Mobile Planetarium project started in 2010 and has reached approximately 500,000 school children to date. However, data collected over the period 2010-2023 showed that certain regions and groups were underrepresented. Therefore, in 2024...

MICADO is a first light instrument for the Extremely Large Telescope. Together with an adaptive optics system, it will make supersharp images of the near-infrared sky (0.8-2.3 micron). The instrument is lead by the Max-Planck Institute for Extraterrestrial physics in Munich. NOVA contributes to this instrument, with the design and manufacturing of 2 filterwheels, a pupilwheel (including...

Enriching press releases and social media posts with short videos is becoming increasingly important. In 2024, the NOVA Information Center experimented with content creation. For example, we produced one-and-a-half minute videos in which we interviewed three researchers per video. In these videos, we also included b-roll footage of telescopes and astronomical phenomena. In this presentation,...

Fast radio bursts (FRBs) are bright, millisecond-duration radio transients with diverse morphologies and uncertain origins. As detection rates accelerate, manual classification becomes impractical. In this talk, I present a new framework for exploring FRB time-frequency structures using unsupervised machine learning techniques. We apply Principal Component Analysis (PCA) and a Convolutional...

We have recently opened a window on the seconds-to-minutes variable radio sky, and through these observations, a new source class of LPTs has begun to emerge. These new transients have emitted unknown radio flares with durations of seconds to minutes and periodicities of minutes to hours (Hyman et al. 2005; Hurley-Walker et al. 2022). These timescales imply that these transients exhibit...

The Mid-Infrared ELT Imager and Spectrograph (METIS) is one of the first-light instruments for Europe’s Extremely Large Telescope (ELT). Covering the L, M, and N bands, METIS will offer imaging, coronagraphy, and medium-resolution spectroscopy across its full wavelength range (3-13 microns), as well as high-resolution integral field spectroscopy in the L and M bands (3-5 microns).

Following...

We would like to present the Black Hole Render Engine for the industry standard, open-source, 3d graphics software Blender. Our render engine has two unique capabilities. First it is able to render images of textured meshes at arbitrarily close and far away positions to a black hole. Secondly, the camera can be freely orientated in spacetime and placed anywhere between far away (for...

Unlucky stars that venture too close to a supermassive black hole (BH) get ripped apart by gravitational tidal forces. These tidal disruption events (TDEs) offer a rare probe of otherwise quiescent BHs.

TDEs are usually detected in the optical and ultraviolet (UV), where light curves show an early-time peak, often followed by a late-time plateau. Recent modelling shows that these plateaus...

Astronomical instrumentation projects are often very international, with team members coming from different cultural backgrounds, being proficient in multiple different languages, working across different time zones, and frequently having a different (professional) understanding of the same – often English – working language.

In this talk, I would like to share my personal and professional...

We see considerable political pressure against "DEI" (Or EDI, Equity, Diversity and Inclusion). We still have more freedom of speech on this than our colleagues in the USA (where I previously lived and worked for 20 years);

We need to address the question of how we can explain to guys like Donald why EDI matters, what it is and what it isn't. Much of the time we are "preaching to the...

The European Regional Office of Astronomy for Development (E-ROAD), part of the International Astronomical Union’s global OAD network, harnesses astronomy to drive societal progress and contribute to the United Nations Sustainable Development Goals (SDGs). Based at Leiden University, E-ROAD focuses on quality education (SDG 4), gender equality (SDG 5), economic growth (SDG 8), and reducing...

Ground-based observations of spacecraft signals have been used to study space weather. However, single spacecraft measurements observed from the Earth have limitations in studying the structure and evolution of solar plasma as they are unable to differentiate spatial and temporal variations. To overcome this limitation and improve our understanding of interplanetary scintillation, we...

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, discuss how anyone can get involved in the SKA now, 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...

DG CVn (GJ3789) is a famous, nearby (18pc) binary consisting of two young M4.0Ve red dwarf stars. It has been the source of the most luminous gamma flare event ever detected by Swift, and produces large flares in the optical and radio as well. Due to a maximum projected separation of only 0.2", it has been difficult to resolve optically, even for the Gaia mission.

One of the binary...

In the last few years, a new class of mysterious periodic radio transients has been discovered, with periods far exceeding those seen on pulsars. These long-period transients (LPTs) produce bright, often strongly polarised emission in pulses that last less than a minute and repeat on a timescale of minutes to hours. The origins of LPTs are largely unknown still, with proposed progenitor...

Ram pressure stripping, i.e. the advection of the interstellar medium (ISM) of galaxies experiencing a intracluster medium (ICM) wind, is a key process responsible for the environmental quenching of star-formation activity in galaxy clusters. This process also affects the non-thermal component of the ISM, i.e. the magnetic fields and cosmic rays, which can be probed in the radio continuum. In...

The Dust Settling Instabilty (DSI) is a member of the Resonant Drag Instabilities (RDI) family, and is thus related to the
Streaming Instability (SI). Linear calculations found that the unstratified monodisperse DSI has growth rates much higher than the SI
even with lower initial dust to gas ratios. However, recent nonlinear investigation found no evidence of strong dust clumping at...

The interplay between gas accretion, feedback, and galactic dynamics plays a crucial role in shaping galaxy evolution. The MHONGOOSE survey, with its unprecedented HI sensitivity and high spatial resolution, provides a transformative opportunity to study these complex processes in nearby galaxies. By probing gas at extremely low column densities in the outskirts of galaxies, MHONGOOSE enables...

Fast Radio Bursts (FRBs) are millisecond-duration radio transients that serve as unique probes of extragalactic matter. We report on the discovery and localization of two FRBs piercing the Andromeda Galaxy (M31) by the realfast fast transient detection system at the Very Large Array. Their unique sightlines allow constraints on M31’s electron density distribution. We localized FRB 20230930A...

The cosmic star-forming activity peaked at redshifts z=1-4 in the so-called "Cosmic Noon". This vigorous star production is driven by massive galaxies with star-formation rates 100-1000x higher than the Milky Way. However, it has long been unclear what causes these immense star formation: were early galaxies forming stars very efficiently, or are they simply more gas-rich than present-day...

The streaming instability is an efficient method for overcoming the barriers to planet formation in protoplanetary discs. The streaming instability has been extensively modelled by hydrodynamic simulations of gas and a single dust size. However, more recent studies considering a more realistic case of a particle size distribution show that this will significantly decrease the growth rate of...

Radio pulsars are fascinating objects that keep delivering important insights into fundamental physics after more than a half century since their discovery. Precise pulsar timing experiments have provided the most stringent constraints on alternative theories of gravity and the equation of state (EoS) of dense matter inside neutron stars. However, the ability to constrain the EoS with binary...

Very Low Mass Stars (VLMSs) are the most abundant stars in our galaxy. The occurrence rate of Earth-like planets orbiting VLMS is higher than for higher-mass stars. Their planet-forming disks evolve fast, which makes them ideal laboratories to study Earth-like planet formation in the evolved disk. The faintness of VLMSs and the small sizes of their disks make their observations challenging....

Most Sun-like stars host planets. Once these stars run out of fuel in the core, they will go through a short red giant phase and end their life as a white dwarf. It is unknown what happens the planetary systems around these stars: does the red giant engulf them, ejected, or are entirely new planets born?

In my talk, I will present the results of a systematic search of Zwicky Transient...

Most Active Galactic Nuclei (AGNs) are thought to contain a molecular and dusty torus that surrounds the accretion disk and obscures the AGN. The high angular resolution of the Atacama Large Millimetre/submillimetre Array (ALMA) allows us to resolve these tori for the first time, opening up the road to answering some long-held questions. One such question is the dynamics of tori and their...

If a system comes very close to a massive black hole it will be disrupted. The rate and type of these disruptions depends on the mechanism by which such a close passage occurs. We present new results showing that the axisymmetry of the potential of a galaxy (using the Milky way as an example) allows for chaotic orbits, a substantial fraction of which can dive arbitrarily close to the galactic...

Oxygen and carbon are key ingredients for the formation of planets. While planet-forming regions around T Tauri stars are typically oxygen-rich, planet-forming regions around very low-mass star (VLMS) are known to exhibit highly carbon-rich environments. Infrared spectroscopy provides a powerful tool to detect and quantify these essential building blocks in protoplanetary disks. In this talk,...

Post-asymptotic giant branch (post-AGB) stars have recently lost their envelopes and are contracting to higher effective temperatures, while maintaining constant luminosity, to become white dwarfs. About half of the optically bright post-AGB stars are found to exhibit near-infrared excesses in their spectral energy distributions, interpreted as hot dusty discs around the objects, and are...

Before the launch of Gaia, eccentricity in wide evolved binaries (with periods of ~10²–10⁴ days) was considered an oddity, as only a few small samples were known. These observations have revealed that many of these systems are eccentric, with the range of observed eccentricities increasing with orbital period. Notably, the maximum observed eccentricities also rise as the orbital period grows....

One of the most ambitious goals of modern astronomy is to uncover signs of extraterrestrial biological activity. This is, primarily achieved through spectroscopic analysis of light emitted by exoplanets to identify specific atmospheric molecules. Most exoplanets are indirectly identified through techniques like transit or Doppler shift of the host star's flux. Long-term surveys have yielded...

Have you ever looked at a dataset and thought, I know the question I want to ask—but how do I actually get the answer? Or perhaps you’ve developed a new method and are wondering where else it could be useful. Maybe you're curious whether others in the Dutch astronomy community are facing similar data challenges, or have already found creative solutions. If so, this session is for you.

Data...

The Advanced Telescope for High-Energy Astrophysics (Athena) has successfully completed a redefinition phase – both of the technical implementation, and mission driving science objectives – becoming ‘NewAthena’. With mission adoption by ESA foreseen in early 2027, the activities of the NewAthena Science Community are expected to ramp up in the very near term. I will give an update on the...

The Africa Millimeter Telescope (AMT) is the first African millimeter-wave radio telescope and will link to the Event Horizon Telescope (EHT) network. The AMT will be built in the Khomas Highlands of Namibia and due to its unique location will be able to contribute significantly to increased angular and temporal resolution of the EHT array. In addition to participation in Very Long Baseline...

Since 2020, Microsoft’s emissions have risen by more than 30%, and Google’s by almost 50%. The reason, according to both companies, is the insatiable energy demand of generative AI. As a result, both companies are now openly wavering on their previous corporate emissions targets and making it clear that AI growth will take priority over achieving any climate goals.

To put it another way:...

The Low Frequency Array (LOFAR) telescope is preparing for a major upgrade, known as LOFAR2.0. In 2025 and 2026 all 16.000 receivers, the station digital beam formers, clock distribution system, data network, correlator/beam former and central processing cluster will be replaced. On top, two new stations in Italy and Bulgaria will be built and added to the telescope.
LOFAR is a pan-European...

The NOVA Submillimeter (submm) Group was established at the Kapteyn Astronomical Institute in 1998 as part of the Netherlands Research School for Astronomy (NOVA) instrumentation effort. Its primary goal was to develop technology for the ALMA project. This focus shaped the group's research and development direction, particularly in the field of low-noise heterodyne receivers for submillimeter...

The impetus for wide-field searches for counterparts of explosive transients including binary neutron-star mergers, supernovae, and tidal disruption events has never been higher. The ongoing operations with the LIGO-Virgo network of gravitational wave detectors in the 4th observing period continues to offer challenges for optical observers, primarily due to the poor (~100 deg$^2$) localisation...

The Habitable Worlds Observatory (HWO) is the next flagship of NASA, planned to be launched in the 2040s. With a wavelength coverage from the ultraviolet to the near-infrared and a suite of multi-purpose instruments, this observatory will be a successor to the Hubble Space Telescope. It will be the first space telescope designed specifically to directly characterize Earth-sized exoplanets...

Gaia is revolutionising our understanding of the Milky Way and can be used for research in many different areas of astronomy, ranging from solar system science to quasars. One field where the Gaia astrometry excels is the study of so-called runaway stars. Runaway stars move away from their birth region with a high peculiar velocity. The high-mass runaway stars can efficiently and effectively...

Constraining the Epoch of Reionization remains one of the pivotal tasks of modern cosmology, and next-generation telescopes are opening up the path to the first precision constraints on the timing of reionization derived from the Lyman-$\alpha$ damping wing signature imprinted on the spectra of high-redshift quasars by the foreground neutral intergalactic medium (IGM). In the coming years,...

Understanding the processes that drive the quenching of star formation in galaxies is crucial for unveiling the mechanisms that shape galaxy evolution. Quenching transforms actively star-forming galaxies into passive systems on very short timescales of a few hundred Myr, influencing the overall structure, morphology, and chemical composition of galaxies across cosmic time. Investigating...

Recently, we have with LOFAR successfully imaged several deep fields at sub-arcsecond resolutions (e.g. Lockman Hole, ELAIS-N1, and Boötes), revealing the distant universe below 200 MHz in unprecedented detail. However, this has come at the expense of significant computing resources and extensive manual intervention, making it unsustainable for large-scale surveys or ultra-deep wide-field...

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,...